Proper Handling of Chemicals and Equipment

· Consider all chemicals to be hazardous unless you are instructed otherwise. Material Safety Data Sheets (MSDS) are available in lab for all chemicals in use. These will inform you of any hazards and precautions of which you should be aware.

· Know what chemicals you are using. Carefully read the label twice before taking anything from a bottle. Chemicals in the lab are marked with NFPA hazardous materials diamond labels. Learn how to interpret these labels.

· Excess reagents are never to be returned to stock bottles. If you take too much, dispose of the excess.

· Many common reagents, for example, alcohols and acetone, are highly flammable. Do not use them anywhere near open flames.

· Always pour acids into water. If you pour water into acid, the heat of reaction will cause the water to explode into steam, sometimes violently, and the acid will splatter.

· If chemicals come into contact with your skin or eyes, flush immediately with copious amounts of water and consult with your instructor.

· Never point a test tube or any vessel that you are heating at yourself or your neighbor--it may erupt like a geyser.

· Dispose of chemicals properly. Unless you are explicitly told otherwise, assume that only water may be put in the lab sinks.

· Clean up all broken glassware immediately and dispose of the broken glass properly.

· Contact the stockroom for clean-up of mercury spills.

· Never leave burners unattended. Turn them off whenever you leave your workstation. Be sure that the gas is shut off at the bench rack when you leave the lab.

Chemistry Laboratory Common Equipment

 

Balance (electronic)	Beakers	Bunsen Burner
Crucible	Crucible Tongs	Pipets
Forceps	Funnels	Graduated Cylinders

Buret & Stand        Flasks        Pipets and Bulbs

"Multielectron atom" and "polyelectronic atom" redirect to here.

The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleuscontains a mix of positively charged protons and electrically neutral neutrons(except in the case of hydrogen-1, which is the only stable nuclide with no neutrons). The electrons of an atom are bound to the nucleus by theelectromagnetic force. Likewise, a group of atoms can remain bound to each other by chemical bonds based on the same force, forming a molecule. An atom containing an equal number of protons and electrons is electrically neutral, otherwise it is positively or negatively charged and is known as an ion. An atom is classified according to the number of protons and neutrons in its nucleus: the number of protons determines the chemical element, and thenumber of neutrons determines the isotope of the element.

Helium atom

An illustration of the helium atom, depicting the nucleus (pink) and the electron cloud distribution (black). The nucleus (upper right) in helium-4 is in reality spherically symmetric and closely resembles the electron cloud, although for more complicated nuclei this is not always the case. The black bar is oneangstrom (10−10 m or 100 pm).

Classification

Smallest recognized division of a chemical element

Properties

Mass range: 1.67×10−27 to 4.52×10−25 kg Electric charge: zero (neutral), or ion charge Diameterrange: 62 pm (He) to 520 pm (Cs) (data page) Components: Electrons and a compact nucleus ofprotons and neutrons

Mendeleev's first periodic table (1869) In 1869, building upon earlier discoveries by such scientists as Lavoisier, Dmitri Mendeleevpublished the first functional periodic table. The table itself is a visual representation of the periodic law, which states that certain chemical properties of elements repeat periodically when arranged by atomic number.

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.

This is an online interactive 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 available.

Old alchemical symbol for gold. Modern element symbols are less ambiguous.

It's easier to navigate the periodic table and write chemical equations and formulae once you know the symbols for the elements. However, sometimes it's easy to confuse symbols of elements with similar names. Other elements have symbols that don't seem to relate to their names at all! For these elements, the symbol usually refers to an older element name that isn't used any more. Here's an alphabetical list of element symbols with the corresponding element name. Keep in mind that the names for the elements (and their symbols) may be different in languages other than English: Ac Actinium, Ag Silver, Al Aluminum, Am Americium, Ar Argon, As Arsenic, At Astatine, Au Gold, B Boron, Ba Barium, Be Beryllium, Bh Bohrium, Bi Bismuth, Bk Berkelium, Br Bromine, C Carbon, Ca Calcium, Cd Cadmium

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   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

Some matter is either smaller or larger than an atom. Examples of chemical species that arenot typically considered atoms includes particles that are components of atoms: protons, neutrons and electrons. Molecules and compounds consists of atoms but are not themselves atoms. Examples of molecules and compounds include salt (NaCl), water (H₂O) and ethanol (CH₂OH). Electrically charged atoms are called ions. They are still types of atoms. Monoatomic ions include H⁺ and O^2-. There are also molecular ions, which are not atoms (e.g., ozone, O₃^-).

All matter consists of particles called atoms. This is a list of the basic characteristics of 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.

Since atomic number is the number of protons in an atom and atomic mass is the mass of protons, neutrons, and electrons in an atom, it seems intuitively obvious that increasing the number of protons would increase the atomic mass. However, if you look at the atomic masses on a periodic table you will see that cobalt (atomic number 27) is more massive than nickel (atomic number 28). Uranium (number 92) is more massive than neptunium (number 93). Different periodic tables even list different numbers for atomic masses. What's up with that, anyway?

The reason increasing atomic number doesn't always equate to increasing mass is because many atoms don't have a number of neutrons equal to the number of protons. In other words, several isotopes of an element may exist. If a sizeable portion of an element of lower atomic number exists in the form of heavy isotopes, then the mass of that element may (overall) be heavier than that of the next element. If there were no isotopes and all elements had a number of neutrons equal to the number of protons, then atomic mass would be approximately twice the atomic number (approximately because protons and neutrons don't have exactly the same mass... the mass of electrons is so small that it is negligible). Different periodic tables give differing atomic masses because the percentages of isotopes of an element may be considered changed from one publication to another.

Definition: An isotope is an Atoms with the same number of protons, but differing numbers of neutrons. Isotopes are different forms of a single element.

Examples: Carbon 12 and Carbon 14 are both isotopes of carbon, one with 6 neutrons and one with 8 neutrons (both with 6 protons).

Definition: Atomic mass or atomic weight is the average mass of atoms of an element, calculated using the relative abundance of isotopes in a naturally-occurring element.

Examples: The atomic mass of carbon is 12.011; the atomic mass of hydrogen is 1.0079

Avogadro’s Number

Avogadro's number is defined as the number of molecules in a gram mole of a particular elemental substance. Avogadro's number is named after the chemist Amedeo Avogadro (1776—1856), who first suggested the idea that elements had particular weights. Avogadro did not actually calculate the value of the number, which has been honorarily named after him. In fact, the term “Avogadro's number” was first used by Jean Baptiste Perrin in 1909 in his paper that followed Einstein's theoretical result and calculated the size of molecules.

So what is Avogadro's number good for? Avogadro's original theory, in 1811, suggested that a particular volume of any gas, at the same temperature and pressure, contained the same number of molecules no matter what gas it was. Experiments were done, and eventually it was concluded that one cubic centimeter of gas contained Avogadro's number of gas molecules, or about 6 × 10²³ molecules.

The current value of Avogadro's number is 6.022 × 10²³, as determined by experiments using X ray diffraction. Avogadro's number is very difficult to determine, and many experiments over the years have refined this current value.

The Mole  Avogadro's number is also used to define the mole. A mole, in addition to a small furry mammal, is defined in chemistry as the amount of a substance that contains Avogadro's number of molecules (or other units). A mole of oxygen contains 6.022 × 1023 oxygen molecules. A mole of sandwiches contains 6.022 × 10²³ sandwiches. That's a lot of peanut butter and jelly!

Avogadro's number can also be used to convert between number and mass. Chemists defined the “atomic mass unit (amu)” as a relative measurement of mass. Since atoms and molecules are difficult to see even with the best microscope, it is nearly impossible to measure the mass of an individual atom. So scientists defined the atomic mass unit as   of the mass of an atom of the element carbon-12.

Molecular Masses The atomic weights of elements, in atomic mass units, are used to line them up sequentially in the periodic table. The atomic mass of carbon-12, for example, is 12 amu, while the atomic mass of oxygen is 16 amu. Due to how atomic masses are defined, then, 12 grams of carbon-12 will contain the same number of atoms as 16 grams of oxygen.

But remember the definition of the mole as 6.022 × 10²³ units. A mole of carbon, for example, will contain 6.022 × 1023 atoms of carbon, which will weigh 12 grams! The conversion from moles to grams depends on the molecular mass of the substance in question. To convert from moles to grams, just multiply by the molecular mass in grams per mole.

Einstein's Role In coming up with a theoretical way to calculate Avogadro's number, Einstein provided essential support to the atomic theory of matter, which was still in question at the time that Einstein wrote his paper. Einstein's theoretical result spurred Perrin to measure Avogadro's number experimentally, thus providing solid experimental proof for the existence of atoms and molecules.

Avogadro's Law Avogadro's law states that equal volumes of gases, at the same temperature and pressure, contain the same number of molecules. Avogadro's hypothesis wasn't generally accepted until after 1858 (after Avogadro's death), when the Italian chemist Stanislao Cannizzaro was able to explain why there were some organic chemical exceptions to Avogadro's hypothesis. One of the most important contributions of Avogadro's work was his resolution of the confusion surrounding atoms and molecules (although he didn't use the term 'atom'). Avogadro believed that particles could be composed of molecules and that molecules could be composed of still simpler units, atoms.The number of molecules in a mole (one gram molecular weight) was termed Avogadro's number (sometimes called Avogadro's constant) in honor of Avogadro's theories. Avogadro's number has been experimentally determined to be 6.023x10²³ molecules per gram-mole.

Chemists use Avogadro's number in many calculations. This constant is the number of particles in a mole of a substance. It's an experimentally derived value that you can determine for yourself. One easy method uses electrochemistry to make the calculation. Current (electron flow) over time is measured in an electrochemical cell. The number of atoms in a weighed sample is related to the current to calculate Avogadro's number.