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Basic Chemistry

• All Matter in universe is composed of Atoms
• Elements are composed of only 1 type of atom.
• Atoms are mostly empty space.
• Atoms have Electrons which are very small and are negatively charged and have a negligible mass (mass = 0).
• Electrons move in orbits around the center of the atom - in relatively distinct areas called Energy Levels.(aka. Orbits or shells)
• The farther from the center an electron is the more energy it has.
• Electrons (& therefor atoms, can gain and lose energy) and do this by moving between energy levels.
• Atoms have a Nucleus which contain Protons & Neutrons.
• Protons are Positively Charged and have a mass =1
• The number of protons in an atom’s nucleus determines what element it is
• Neutrons have no charge and are therefor called Neutral and have a mass = 1.

• Chemical elements are represented on the periodic table using the above format.
• The letter is an abbreviation of Element Name
• Atomic Number is the number is the number of protons the atom has. It is the number of protons an element has which determines what element it is.
• Mass number is the total mass of an atom in AMU. It is the same as the number of protons & neutrons of the element. One can calculate the number of neutrons an atom has by subtracting the atomic number (# protons) from the mass number. Mass number CAN change without changing the identity of the element.
• Atoms having the same atomic numbers and different mass numbers are called Isotopes.

• Isotopes are atoms of the same element with different numbers of neutrons (mass).
• They react chemically the same as the "normal" form of the element
• They are frequently radioactive

Interactions of matter:

• Atoms interact through the process of chemical bonding.
• Process is determined by the number of electrons found in the outermost energy level of an atom.
• Involves the transfer & sharing of electrons between atoms.
• ELECTRON / ENERGY LEVEL RULES:
• Atoms in a neutral state have an equal number of protons and electrons.
• Atoms "fill up" their energy levels from the lowest to the highest. Electrons rarely "skip" levels.
• The 1^st Energy level can only hold 2 electrons
• The 2^nd and 3rd energy levels can only hold 8 electrons
• Atoms seek to have a "full" outermost energy level. All chemical reactions happen to accomplish this

• When a Chemical Reaction occurs atoms gain, lose or share electrons.
• Atoms always want to have their outer energy level "full" of electrons
• When an atom has a different number of protons & electrons it is called an Ion.
• If an ion has more protons than electrons - it is Positively Charged
• If an atom has more electrons than protons it is Negatively Charged.
• Atoms of opposite charge are attracted to each other.
• There are three types of chemical bonds. Ionic bonds, Covalent Bonds, & Metallic Bonds.
• Ionic bonds form when 1 atom "gives" one or more electrons to another atom.
• This results in 1 positively charged ion & 1 negatively charged ion
• Since opposite charges attract, they come together and bond
• Covalent bonds form when 2 atoms "share" one or more electrons between them.
• There are 2 types of covalent bonds:
• Non-Polar Covalent bonds form when two atoms share electrons equally
• Polar Covalent bonds form when two atoms share electrons unequally.
• Atoms can share more than 1 electron between them forming multiple bonds
• A Molecule is a group of 2 or more atoms held together by covalent bonds.

Summary of Ionic & Covalent Bonds

• A Chemical Reaction = whenever a chemical bond is formed or broken.
• 2 types (sometimes 3) of substances with chemical reactants
• Reactants = Substances existing before the reaction
• Products = Substances existing after the reaction
• Catalysts = Substances which speed up the rate of a reaction
• Chemical Equations are a shorthand way of showing chemical reactions.
• Separates Products and reactants.
• Usually follow flow of energy.
• Rx’s naturally occur when they release energy
• Can however occur when energy is added.

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Mr. Stanley

Last Updated: March 11, 2004