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Saturday, May 9, 2009

Cyclic alkanes and conformations

Naming cyclic alkanes

First you would count the longest carbon chain. You can see that the "cyclic" ring has 8 carbons, so it's octane. Since it's a cyclic ring, you call it a "cyclo" alkane. Hence, the main part of the molecule would be called cyclooctane. The substituent is called a methyl group, so you get the name methylcyclooctane.

Now, the hard part of this is figuring out numberings. You can pick ANY carbon to be "1," so we'll conveniently choose the carbon that the methyl is on as methylcyclooctane. It wouldn't matter if the methyl group was on the top right carbon, because it would still be methylcyclooctane, because you could rotate that molecule to get the one above. Now, let's try two substituents.

We again know it's a cyclooctane, but the problem arises in how to number the substituents. We could name this 1-methyl-3-ethylcyclooctane, or 1-ethyl-3-methylcyclooctane. We name it 1-ethyl-3-methylcyclooctane because of the alphabetization rules. Also, priority is given to the longest carbon chain substituent in naming (so we wouldn't name it 3-ethyl-1-methylcyclooctane).

These are some ways to draw the same compound, cyclohexane. Cyclohexane is a pretty important molecule, and I guarantee you will see these again.

Basically the last two are cyclohexane drawn the way it really does look. The 2nd drawing is for "watered down" organic that is taught to AP Chemistry students. If you take a real orgo class (although I've only taken an intro course) you will learn all sorts of cool stuff like that.

Now, with the 4th cyclohexane, there are two positions for atoms.

Note that this is the same molecule as the top right cyclohexane, except I've drawn in all the hydrogens.

The lines going up and down are considered the "axial" position, while the ones going right and left are considered "equatorial." Now, guess which position is more stable. The equatorial is! If you have an axial position, there is steric repulsion between all the axial atoms.

How to Get Mosquitoes to Bite Your Friends

... not that actually want mosquitoes to bite your friends, but I think you will agree you don't want to be bitten. Here's a list of things that attract mosquitoes. If you want to avoid an encounter with the vampiric swarm you can avoid doing any of these things yourself or you can encourage those around you to do them. Whatever works. Wear Dark Clothing
Many mosquitoes use vision to locate hosts from a distance. Dark clothes and foliage are initial attractants.

You give off more carbon dioxide when you are hot or have been exercising. A burning candle or other fire is another source of carbon dioxide.

Eat Bananas and French Fries
You release more lactic acid when you have been exercising or after eating certain foods (e.g., salty foods, high-potassium foods).

Wear Perfume or Cologne
In addition to perfumes, hair products, and scented sunscreens, watch for the subtle floral or fruity fragrances from fabric softeners and dryer sheets.

Have Cold Hands
Mosquitoes are attracted by a particular temperature range. The exact temperature depends on the type of mosquito. Many mosquitoes are attracted to the slightly cooler temperatures of the extremities.

Perspire, Swim, or Play in the Sprinkler
Mosquitoes are attracted by perspiration because of the chemicals it contains and also because it increases the humidity around your body. Even small amounts of water (e.g., moist plants or mud puddles) will draw mosquitoes. Standing water also allows mosquitoes to reproduce.

Wear Dark Clothing
Many mosquitoes use vision to locate hosts from a distance. Dark clothes and foliage are initial attractants.

You give off more carbon dioxide when you are hot or have been exercising. A burning candle or other fire is another source of carbon dioxide.

Eat Bananas and French Fries
You release more lactic acid when you have been exercising or after eating certain foods (e.g., salty foods, high-potassium foods).

Wear Perfume or Cologne
In addition to perfumes, hair products, and scented sunscreens, watch for the subtle floral or fruity fragrances from fabric softeners and dryer sheets.

Have Cold Hands
Mosquitoes are attracted by a particular temperature range. The exact temperature depends on the type of mosquito. Many mosquitoes are attracted to the slightly cooler temperatures of the extremities.

Perspire, Swim, or Play in the Sprinkler
Mosquitoes are attracted by perspiration because of the chemicals it contains and also because it increases the humidity around your body. Even small amounts of water (e.g., moist plants or mud puddles) will draw mosquitoes. Standing water also allows mosquitoes to reproduce.

I am a veritable mosquito magnet. I wear a lot of black, favor Coppertone™ when outdoors (bloodsuckers seem to love the subtle jasmine scent of that sunscreen), and can be found near the beach or poking at the barbeque, sipping a sports drink or fruity drink. Don't be like me! Or if you are, try one of these natural mosquito repellents.

Friday, May 8, 2009

Alkane Nomenclature:

Learning how to name alkanes will be crucial in your understanding of organic chemistry. All organic compounds are named following a certain set of rules set out by the IUPAC. By memorizing these rules, you should be able to name all compounds.

To name alkanes....
(follow these set of rules)

1.) Count the longest carbon chain

If the carbon chain is:
  • 1 carbon: named "methane"
  • 2 carbons: named "ethane"
  • 3 carbons: named "propane"
  • 4 carbons: named "butane"
  • 5 carbons: named "pentane"
  • 6 carbons: named "hexane"
  • 7 carbons: named "heptane"
  • 8 carbons: named "octane"
  • 9 carbons: named "nonane"
  • 10 carbons: named "decane"

Note that organic chemists, being lazy, will often not label hydrogens or carbons. For instance,

would be hexane (each of the "points" is assumed to be a carbon)

2.) Number the carbon chain, starting with the end closest to the substituent. Always try to get the lowest number possible.

If there are two substituents, name the carbon chain so that it has the lowest possible number.For instance, check out this molecule:

Would this compound be numbered from the left or right? The answer is that it would be answered from the right. If the molecule was named from the left, you would have substituents on carbons 3 and 5. Numbering from the right, the subsituents are on carbons 2 and 4.

Once you have determined which direction you will name, you will have to write down the molecule.

3.) Name and number the substituent

When naming, name the substituent before the parent chain.
Name this compound:

  • The longest carbon chain is 6 carbons. Hence the parent chain is named "hexan
  • Two subsituents are located on carbons 2 and 3, not 4 and 5.
  • There are two "methyl" substituents
  • Hence, we have the name, 2,3-dimethylhexane

If you have two substituents that are not the same, then you must name them both before the parent chain, listed alphabetically. Note that the prefixes used to designate number (i.e. di and tri) do not affect the alphabetization.
Name this compound:

  • The longest parents chain is 6 carbons, hence its parent name is "hexane"
  • I spy, with my own eyes, three substituents! There are two methyl and one ethyl group. How should I number them? Well, seeing as to how I can get 2,3,4 instead of 3,4,5, I shall name them from the left.
  • So the substituents are 2,4-dimethyl and 3-ethyl. Note that "e" in ethyl precedes "m" in "methyl. The "di" doesn't affect the alphabetization

  • Finally, we name the compound as
  • 3-ethyl-2,4-dimethylhexane.

Alkane Reactions:

All single chain hydrocarbons will combust into carbon dioxide and water completely

Halogenation of an alkane. This reaction takes an unreactive molecule (methane) and makes it very reactive (chloromethane).

Thursday, May 7, 2009

Reactions(SN1, SN2, E1, E2)

Two extremily common reactions in Organic Chemistry are substitution and elimination reactions. We are going to cover four basic reactions, E1, E2, SN1, and SN2. These reactions all compete with each other so be sure to pay attention to which conditions fovor each reaction.

The most common is called an SN2 reaction. It is a simple nucleophilic attack of a nucleophile onto an electrophilic carbon. This attack causes and inversion of absolute configuration of the carbon center.

  •   SN2 Nucleophilic Substitution causes inversion of configuration: (best in polar aprotic solvents, strong nucleophiles and good leaving groups.)

 Going from (R) to (S)


If Carbon is tertiary and nucleophile is weak then it undergoes SN1 reaction: j has same products as SN2 but is racemised and best in polar protic solvent and the reaction is 1st order, not 2nd...

-racemization is when there is the absolute configuration of the carbon center is not either retained or inverted but rather randomized.

-1st order means it takes place in one rate limiting step, as opposed to the SN2 and E2 which you will learn about next, which have 2 steps.


Another type of reaction is an elimination reaction. In an elimination reaction, instead of substitute the leaving group with a nucleophile, it is removed and a double bond is formed in the compound.

Stuff in favor of SN2 over E2: Low temperature; Modest bases, nucloephiles; Sterically small bases; Primary is best, tertiary is worst


E1 reactions occur under similiar conditions to the S1 reaction, but instead of having substitution, elimination occurs. E1 vs SN1: both are good with weak nucleophiles and polar protic solvents; both want a good leaving group; tertiary substrates; if SN1, then E1 present too; these two reactions are always competing.

Wednesday, May 6, 2009

College Science Fair Project

Get Science Fair Project Ideas

It can be a challenge to come up with a science fair project idea. There is fierce competition to come up with the coolest idea, plus you need a topic that is considered appropriate for your educational level. I've arranged science fair project ideas by topic, but you might like to take a look at ideas according to education level.

A well-designed project at the college level can open the door to future educational and career opportunities, so it pays to put some thought and effort into your topic. Answer a question, test a hypothesis. College students usually have a semester to complete their project, so you have some time to plan and conduct your research. The goal at this level is to find an original topic. It doesn't have to be something complicated or time-consuming. Also, appearances count. Aim for professional-quality images and presentation. Handwritten work and drawings won't work as well as a printed report or poster with photographs.

Does the presence of detergent in water affect plant growth? In what ways? What is the implication regarding water pollution?

Does magnetism affect the growth of plants? In what way?

How does the shape of an ice cube affect how quickly it melts?

Do the same types of mold grow on all types of bread? Are certain preservatives better at inhibiting dangerous molds than others?

Is the nutritional content of different brands of a vegetable (e.g., canned peas) the same? How much variation is there in any given product?

Do consumers prefer bleached paper products or natural-color paper products? What factors affect the preference? Age? Socio-economic status? Gender?

Is a seed affected by its size? Do different size seeds have different germination rates or percentages? Does seed size affect the growth rate or final size of a plant?

How does cold storage affect the germination of seeds? Factors you can control include the type of seeds, length of storage, temperature of storage, and other variables, such as light and humidity.

Elementary School Science Fair Projects

Get Science Fair Project Ideas

It can be challenging to think
of a good project idea.
H. Berends, stock.xchng

It can be a challenge to come up with a science fair project idea. There is fierce competition to come up with the coolest idea, plus you need a topic that is considered appropriate for your educational level. I've arranged science fair project ideas by topic, but you might like to take a look at ideas according to education level.
Elementary School Science Fair Project Tips

Elementary school projects aren't supposed to be rocket science (though of course they could be). Look for a project that you can do over a fairly short time span, such as over a weekend. Keep in mind, judges will disqualify you if they suspect your parents did the project and not you, so though you may get help from adults, be sure the project is really yours. Resist the temptation to make a display or do a demonstration. Try to answer a question or solve a problem.

Can you predict what things will glow under a black light?
Will chilling an onion before cutting it keep you from crying?
What ratio of vinegar to baking soda produces the best chemical volcano eruption?
What type of plastic wrap best prevents evaporation?
What plastic wrap best prevents oxidation?
Are night insects attracted to lamps because of heat or light?

Atoms and Atomic Theory

Chemistry is the study of matter and the interactions between different types of matter and energy. The fundamental building block of matter is the atom. An atom consists of three main parts: protons, neutrons, and electrons. Protons have a positive electrical charge. Neutrons have no electrical charge. Electrons have a negative electrical charge. Protons and neutrons are found together in what is called the nucleus of the atom. Electrons circle around nucleus.

Chemical reactions involve interactions between the electrons of one atom and the electrons of another atom. Atoms which have different amounts of electrons and protons have a positive or negative electrical charge and are called ions. When atoms bond together, they can make larger building blocks of matter called molecules.

All matter consists of particles called atoms. Here are some useful facts about atoms:

Atoms cannot be divided using chemicals. They do consist of parts, which include protons, neutrons, and electrons, but an atom is a basic chemical building block of matter.

Each electron has a negative electrical charge.

Each proton has a positive electrical charge. The charge of a proton and an electron are equal in magnitude, yet opposite in sign. Electrons and protons are electrically attracted to each other.

Each neutron is electrically neutral. In other words, neutrons do not have a charge and are not electrically attracted to either electrons or protons.

Protons and neutrons are about the same size as each other and are much larger than electrons.

The mass of a proton is essentially the same as that of a neutron. The mass of a proton is 1840 times greater than the mass of an electron.

The nucleus of an atom contains protons and neutrons. The nucleus carries a positive electrical charge.

Electrons move around outside the nucleus.

Almost all of the mass of an atom is in its nucleus; almost all of the volume of an atom is occupied by electrons.

The number of protons (also known as its atomic number) determines the element. Varying the number of neutrons results in isotopes. Varying the number of electrons results in ions. Isotopes and ions of an atom with a constant number of protons are all variations of a single element.

The particles within an atom are bound together by powerful forces. In general, electrons are easier to add or remove from an atom than a proton or neutron. Chemical reactions largely involve atoms or groups of atoms and the interactions between their electrons.

Acids and Bases Definitions Introduction to Key Terms & Concepts

There are several methods of defining acids and bases. While these definitions don't contradict each other, they do vary in how inclusive they are. Antoine Lavoisier, Humphry Davy, and Justus Liebig also made observations regarding acids and bases, but didn't formalize definitions.

Sulfuric acid can donate two
protons or hydrogen ions
in an aqueous solution.
Ben Mills

Svante Arrhenius

acids produce H+ ions in aqueous solutions
bases produce OH- ions in aqueous solutions

water required, so only allows for aqueous solutions
only protic acids are allowed; required to produce hydrogen ions
only hydroxide bases are allowed

Johannes Nicolaus Brønsted - Thomas Martin Lowry

acids are proton donors
bases are proton acceptors
aqueous solutions are permissible
bases besides hydroxides are permissible
only protic acids are allowed

Gilbert Newton Lewis

acids are electron pair acceptors
bases are electron pair donors
least restrictive of acid-base definitions

Properties of Acids

taste sour (don't taste them!)... the word 'acid' comes from the Latin acere, which means 'sour'
acids change litmus (a blue vegetable dye) from blue to red
their aqueous (water) solutions conduct electric current (are electrolytes)
react with bases to form salts and water
evolve hydrogen gas (H2) upon reaction with an active metal (such as alkali metals, alkalin
e earth metals, zinc, aluminum)

Properties of Bases

taste bitter (don't taste them!)
feel slippery or soapy (don't arbitrarily touch them!)
bases don't change the color of litmus; they can turn red (acidified) litmus back to blue
their aqueous (water) solutions conduct and electric current (are electrolytes)
react with acids to form salts and water

Examples of Common Acids

citric acid (from certain fruits and veggies, notably citrus fruits)
ascorbic acid (vitamin C, as from certain fruits)
vinegar (5% acetic acid)
carbonic acid (for carbonation of soft drinks)
lactic acid (in buttermilk)

Examples of Common Bases
  • detergents
  • soap
  • lye (NaOH)
  • household ammonia (aqueous)

Acids and Bases Definitions Introduction to Key Terms & Concepts

Virtual Chemistry Text : Acids & Bases

Virtual Chemistry Text Table of Contents

The citric acid and ascorbic
acid in a lemon are both weak acids.

There are several ways to define acids and bases. One way is to look at hydrogen ion concentration. No matter which method you choose, these categories of chemicals participate in some very important reactions. Learn about acids, bases, and pH.

Tuesday, May 5, 2009

Basic Chemistry Concepts


A knowledge of basic chemistry is important for understanding just about any area of biology from the function of cells to the behavior of organisms and the ecological relationships between organisms and their environment.

Indeed, chemists are fond of teasing biologists by claiming that all biology is chemistry*. While this isn't quite true, in order to make sense of the structure of cells and organisms a little chemistry goes a long way.

Ball and Stick" Model of a Heme group. This group is part of a larger molecule, hemoglobin. Grey=Carbon, Blue= Nitrogen, Red= Oxygen. Hydrogens not shown.

*Of course the physicists say that all chemistry is physics!

Electrons, Chemical Bonds and Periodic Table.

The chemical properties of an atom are determined largely by how full or empty the outer electron shell is. For example, atoms of fluorine(F), chlorine(Cl) and the other elements in that second from the last column of the periodic table need only one electron to fill the outer shell. These atoms have a very strong tendency to steal electrons from other atoms. Oxygen and sulphur have 6 electrons in their outer shell which again holds 8 maximum. Thus these elements tend to steal electrons.
Elements such as Lithium(Li) Sodium(Na) and Potassium(K) on the left hand side of the periodic table have an almost empty shell and these elements readily give up those outer shell electrons to atoms such as oxygen and chlorine. Elements that tend to give up electrons to other atoms are called metals.

Elements in the middle of the periodic table tend to share electrons rather than give them up or take them entirely. Many of these such as iron, copper or gold are also considered metals.

The elements at the far right: Helium, Neon, Argon etc... are chemically inert because they have a full outer shell. They will only react with other chemicals under very special conditions. These elements are sometimes called the 'noble' or inert gases because it is so difficult to get them to form chemical bonds.

Electronegativity: The tendency of atoms to grab electrons is called electronegativity. Here is a periodic table showing relative electronegativities. Higher electronegativites are shown in blue. Notice Fluorine(F) is the most electronegative element. Oxygen and chlorine less so.

Note that many of the elements we think of as metals iron(Fe), nickel(Ni), Copper(Cu), Silver(Ag) are intermediate in electronegativity between the metals in red on the far left of the table(low electronegativity) and the column near the right that contains fluorine(F). But real strong metals such as sodium or potassium ready give up electrons.

So the rule of thumb is atoms of the elements on the left side of the periodic table have a tendency to give up their electrons to atoms of the elements in the row beginning with chlorine. This is important because it dicatates the kinds of chemical bonds there elements will form with each other.

Chemical Bonds.

A chemical bond is an attraction between atoms brought about by a sharing of electrons between to atoms or a complete transfer of electrons. There are three types of chemical bonds: Ionic, Covalent and Polar covalent. In addition chemists often recognise another type of bond called a hydrogen bond.

Ionic Bonds:
  Ionic  bonds arise from elements with low electronegativity(almost empty outer shells) reacting with elements with high electronegativity (mostly full outer shells). In this case there is a complete transfer of electrons

A well known example is table salt, sodium chloride. Sodium gives up its one outer shell electron completely to chlorine which needs only one electron to fill its shell. Thus, the attraction between these atoms is much like static electricity since opposite charges attract.

Covalent bond:

Ionic, Covalent, Polar covalent, Hydrogen bond .

   Covalent bonds involve a complete sharing of electrons and occurrs most commonly between atoms that have partially filled outer shells or energy levels. Thus if the atoms are similar in negativity then the electrons will be shared. Carbon forms covalent bonds. The electrons are in hybrid orbitals formed by the atoms involved as in this example: ethane. Diamond is strong because it involves a vast network of covalent bonds between the carbon atoms in the diamond.

Polar Covalent Bond:
 These bonds are in between covalent and ionic bonds in that the atoms share electrons but the electrons spend more of their time around on atom versus the others in the compound. This type of bond occurs when the atoms involved differ greatly in electronegativity. The most familiar example is water. Oxygen is much more electronegative than hydrogen, and so the electrons involved in bonding the water molecule spend more time there.

The fact that water is a polar covalently bonded moleccule has a number of implications for molecules that are disolved in water. In particular, molecules with polar covalent bods can break apart when they encounter water molecules. They are broken apart because of the electrical attraction between the dissimilar charges of the molecules. Also, since ionically bonded molecules involve ions with opposite charges, water with its polar covalent bonds can separate ions from each other and then surround the ions which prevents them from recombining. The properties of water all relate to this polar covalent bonding. Indeed the sorts of so called hydrophilic and hydrophobic interactions water has with varios organic compounds depend on the nature of the polar covalent bond in water.

Hydrogen Bond.

The fact that the oxygen end of a water molecule is negatively charged and the hydrogen end positively charged means that the hydrogens of one water molecule attract the oxygen of its neighbor and vice versa. This is because unlike charges attract. This largely electrostatic attraction is called a hydrogen bond and is important in determining many important properties of water that make it such an important liquid for living things. Water can also form this type of bond with other polar molecules or ions such as hydrogen or sodium ions. Further, hydrogen bonds can occurr within and between other molecules. For instance, the two strands of a DNA molecule are held together by hydrogen bonds. Hygrogen bonding between water molecules and the amino acids of proteins are involved in maintaining the protein's proper shape.

This picture represents a small group of water molecules. Hydrogen bonds between unlike charges are shown as lines without arrows on the ends. The double arrowed lines represent the fact that like charges repell each other. Both hydrogen bonds and the repelling forces balance each other and are both are important in determining the properties of water.

Properties of Water

Water has a number of unusual properites which come about because the atoms that comprise a water molecule form apolar covalent bonds. The main properties of water that are important for living things are the following:

Ice floats. Usually when a liquid freezes the solid ismore dense than the liquid. In water thesolidphase is less dense than the liquid phase under normal conditions. If ice sank, ponds and lakes would freeze solid to the bottom making things very difficult for fish and other creatures to obtain food and oxygen in the winter.

Water is a great solvent especially for polar molecules of ionically bonded substances like salt. That's because the charged ends of the water molecules are attracted to the charges on other molecules. Water molecules will surround soluable molecules or ions in a hydration shell. This helps keep the molecules in solution.

Many gases dissolve in water because the the combination of attractive and repulsive forces among water molecules leaves space for the gas molecules that in most other liquids would not be there. The two gasses we are most concerned about dissolving are carbon dioxide and oxygen.

Water has a high latent heat. Water can store more heat per volume than just about any common substance and releases the heat slowly. This helps moderate the climate.

Has a high heat of vaporization. It takes a lot of heat to break the hydrogen bonds in water and when they braek, the heat energy is carried off as water vapor. This makes water useful as a coolent for large critters like mammals.

Water is cohesive. Water molecules tend to stick together, up to a point. Many insects take advantage of the surface tension brought about at the surface of lakes and pond by cohesion to walk on the surface of the water.

Water is adhesive. Sicks to surfaces with polar groups such as cellulose.

Water disassociates to form hydrogen ions(H+) and hydroxyl (OH-) in small quanitities. This is important for living things because the number of ions in the solutions inside organisms affects the shape and functioning of many of the molecules. The concentration of hydrogen ions in a solution is so important that scientists use a special scale, the pH scale to measure this concentration.

Fatty acids

Fatty acids are organic acids which have a long chain of carbon and hydrogens attached to the carboxyl group. Oleic Acid is a common saturated fatty acid. Actually the bend in the carbon chain suggests that oleic acid is not completely saturated.

I can't resist this cool looking fatty acid from Chrysanthamums. Notice the interesting triangular ring in the carbon chain.

Finally this exotic looking fatty acid is vitamin A

Organic acids.

Organic acids are very important compounds in living things. They are important components of structural molecules such as phospholipids and are an important source of energy.

Organic acids have a carboxyl group and long a chain of carbons attached to it.

This diagram shows formic acid, the simplest organic acid. The name formic comes from the Latin word(Formica) for ant. This acid is an important alarm and defensive compound for many ants.

Acetic acid, the acid in vinegar, has one more carbon than formic acid.

Carbon: the Three Main Forms of the Element


Carbon is important in biology because carbon forms the "back-bone" of just about all biologically important molecules. This is because carbon forms long and sometimes complex covalently bonded structures and also because carbon compounds vary greatly in the type of interactions they have with water. For example some carbon compounds, such as most lipids, have strictly hydrophobic interactions with water, others such as sugars are hydrophilic. Still others such as proteins and phospholipids are partly hydrophobic and partly hydrophilic.




The pH Scale.

The concentration of hydrogen ions in a solution is very important for living things. This is because, since the hydrogen ions are positively charged they alter the charge environment of other molecules in solution. By putting different forces on the molecules, the molecules change shape from their normal shape. This is particularly important for proteins in solution because the shape of a protein is related to its function.

The concentration of hydrogen ions is commonly expressed in terms of the pH scale. Low pH corresponds to high hydrogen ion concentration and vice versa. A substance that when added to water increases the concentration of hydrogen ions(lowers the pH) is called an acid. A substance that reduces the concentration of hydrogen ions(raises the pH) is called a base. Finally some substances enable solutions to resist pH changes when an acid or base is added. Such substances are called buffers. Buffers are very important in helping organisms maintain a relatively constant pH.

Study the pH chart given below carefully. Note that each decrease in pH by one pH unit means a tenfold increase in the concentration of hydrogen ions.

The Periodic Table

The periodic table is an arrangement of the elements by increasing atomic number. Since the electrons add to energy levels in a regular pattern, elements with similar chemical properties tend to repeat themselves with a set period. This allows the table to be constructed such that elements that are most alike in chemical properties are in the same column.

The first view shows an abbreviated version of the periodic table from the Las Alomos National Laboratory.

Sunday, May 3, 2009

Element List

<><>Atomic Number, Element Symbol & Element Name<><>
Here's a list of chemical elements ordered by increasing atomic number. The names and element symbols are provided.

1 - H - Hydrogen
2 - He - Helium
3 - Li - Lithium
4 - Be - Beryllium
5 - B - Boron
6 - C - Carbon
7 - N - Nitrogen
8 - O - Oxygen
9 - F - Fluorine
10 - Ne - Neon
11 - Na - Sodium
12 - Mg - Magnesium
13 - Al - Aluminum, Aluminium
14 - Si - Silicon
15 - P - Phosphorus
16 - S - Sulfur
17 - Cl - Chlorine
18 - Ar - Argon
19 - K - Potassium
20 - Ca - Calcium
21 - Sc - Scandium
22 - Ti - Titanium
23 - V - Vanadium
24 - Cr - Chromium
25 - Mn - Manganese
26 - Fe - Iron
27 - Co - Cobalt
28 - Ni - Nickel
29 - Cu - Copper
30 - Zn - Zinc
31 - Ga - Gallium
32 - Ge - Germanium
33 - As - Arsenic
34 - Se - Selenium
35 - Br - Bromine
36 - Kr - Krypton
37 - Rb - Rubidium
38 - Sr - Strontium
39 - Y - Yttrium
40 - Zr - Zirconium
41 - Nb - Niobium
42 - Mo - Molybdenum
43 - Tc - Technetium
44 - Ru - Ruthenium
45 - Rh - Rhodium
46 - Pd - Palladium
47 - Ag - Silver
48 - Cd - Cadmium
49 - In - Indium
50 - Sn - Tin
51 - Sb - Antimony
52 - Te - Tellurium
53 - I - Iodine
54 - Xe - Xenon
55 - Cs - Cesium
56 - Ba - Barium
57 - La - Lanthanum
58 - Ce - Cerium
59 - Pr - Praseodymium
60 - Nd - Neodymium
61 - Pm - Promethium
62 - Sm - Samarium
63 - Eu - Europium
64 - Gd - Gadolinium
65 - Tb - Terbium
66 - Dy - Dysprosium
67 - Ho - Holmium
68 - Er - Erbium
69 - Tm - Thulium
70 - Yb - Ytterbium
71 - Lu - Lutetium
72 - Hf - Hafnium
73 - Ta - Tantalum
74 - W - Tungsten
75 - Re - Rhenium
76 - Os - Osmium
77 - Ir - Iridium
78 - Pt - Platinum
79 - Au - Gold
80 - Hg - Mercury
81 - Tl - Thallium
82 - Pb - Lead
83 - Bi - Bismuth
84 - Po - Polonium
85 - At - Astatine
86 - Rn - Radon
87 - Fr - Francium
88 - Ra - Radium
89 - Ac - Actinium
90 - Th - Thorium
91 - Pa - Protactinium
92 - U - Uranium
93 - Np - Neptunium
94 - Pu - Plutonium
95 - Am - Americium
96 - Cm - Curium
97 - Bk - Berkelium
98 - Cf - Californium
99 - Es - Einsteinium
100 - Fm - Fermium
101 - Md - Mendelevium
102 - No - Nobelium
103 - Lr - Lawrencium
104 - Rf - Rutherfordium
105 - Db - Dubnium
106 - Sg - Seaborgium
107 - Bh - Bohrium
108 - Hs - Hassium
109 - Mt - Meitnerium
110 - Ds - Darmstadtium
111 - Rg - Roentgenium
112 - Uub - Ununbium
113 - Uut - Ununtrium
114 - Uuq - Ununquadium
115 - Uup - Ununpentium
116 - Uuh - Ununhexium
117 - Uus - Ununseptium
118 - Uuo - Ununoctium

Periodic Table of the Elements

Click on an element symbol in the periodic table to get facts for that element. Printable periodic tables and a list of elements by increasing atomic number are also availab

What Is a Mole and Why Are Moles Used

Question: What Is a Mole and Why Are Moles Used?

Answer: A mole is simply a unit of measurement. Units are invented when existing units are inadequate. Chemical reactions often take place at levels where using grams wouldn't make sense, yet using absolute numbers of atoms/molecules/ions would be confusing, too.

Like all units, a mole has to be based on something reproducible. A mole is the quantity of anything that has the same number of particles found in 12.000 grams of carbon-12. That number of particles is Avogadro's Number, which is roughly 6.02x1023. A mole of carbon atoms is 6.02x1023 carbon atoms. A mole of chemistry teachers is 6.02x1023 chemistry teachers. It's a lot easier to write the word 'mole' than to write '6.02x1023' anytime you want to refer to a large number of things! Basically, that's why this particular unit was invented.

Why don't we simply stick with units like grams (and nanograms and kilograms, etc.)? The answer is that moles give us a consistent method to convert between atoms/molecules and grams. It's simply a convenient unit to use when performing calculations. Okay... you may not find it too convenient when you are first learning how to use it, but once you become familiar with it, a mole will be as normal a unit as, say, a dozen or a byte.

Molecular Weight and Formula Weight

The molecular weight of a molecule is calculated by adding the atomic weights (in atomic mass units or amu) of the atoms in the molecule. The formula weight of an ionic compound is calculated by adding its atomic weights according to its empirical formula.

*The Mole

A mole is defined as the quantity of a substance that has the same number of particles as are found in 12.000 grams of carbon-12. This number, Avogadro's number, is 6.022x1023. The mass in grams of one mole of a compound is equal to the molecular weight of the compound in atomic mass units. One mole of a compound contains 6.022x1023 molecules of the compound. The mass of 1 mole of a compound is called its molar weight or molar mass. The units for molar weight or molar mass are grams per mole. Here is the formula for determining the number of moles of a sample:

mol = weight of sample (g) / molar weight (g/mol)

Molecules and Moles

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Molecules and Moles

A molecule is a combination of two or more atoms that are held together by covalent bonds. A molecule is the smallest unit of a compound that still displays the properties associated with that compound. Molecules may contain two atoms of the same element, such as O2 and H2, or they may consist of two or more different atoms, such as CCl4 and H2O. In the study of chemistry, molecules are usually discussed in terms of their molecular weights and moles.

Ionic compounds, such as NaCl and KBr, do not form true molecules. In their solid state, these substances form a three-dimensional array of charged particles. In such a case, molecular weight has no meaning, so the term formula weight is used instead.

নেপালের প্রধানমন্ত্রী খাদগা প্রসাদ শর্মাকে ফোন দিয়েছেন প্রধানমন্ত্রী শেখ হাসিনা

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