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)
- All Matter in universe is composed of Atoms
Atoms have a Nucleus
which contain Protons & Neutrons.
- The farther from the center an electron is the more energy it
- Electrons (& therefor atoms, can gain and lose energy)
and do this by moving between energy levels.
- Protons are Positively Charged and have a mass =1
- The number of protons in an atoms nucleus determines
what element it is
- Neutrons have no charge and are therefor called Neutral and have a mass = 1.
The "basic" Atom
Summary of Subatomic Particles:
Levels / orbits
Periodic Table Notation:
- Chemical elements are represented on the periodic table using
the above format.
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.
- The letter is an abbreviation of Element Name
- 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
Example Isotopes: Hydrogen
Interactions of matter:
Atoms interact through the process of chemical bonding.
ELECTRON / ENERGY LEVEL RULES:
- 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 in a neutral state have an equal number of protons and
- Atoms "fill up" their energy levels from the lowest
to the highest. Electrons rarely "skip" levels.
- The 1st Energy level can only hold 2 electrons
- The 2nd and 3rd energy levels can only hold 8
- 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.
When an atom has a different number of
protons & electrons it is called an Ion.
- Atoms always want to have their outer energy level
"full" of electrons
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.
- If an ion has more protons than electrons - it is Positively Charged
- Ionic bonds form when 1 atom "gives" one or more
electrons to another atom.
- This results in 1 positively charged ion & 1 negatively
- 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
- A Molecule
is a group of 2 or more atoms held together by covalent bonds.
Summary of Ionic &
- A Chemical Reaction = whenever a chemical bond is formed or
- 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
- Separates Products and reactants.
- Usually follow flow of energy.
- Rxs naturally occur when they release energy
- Can however occur when energy is added.
Structural Formulas are
used to graphically represent a chemical formula
- Useful in visualizing how chemicals react and form new ones.
- When drawing them use the following rules:
- The Periodic table abbreviation is used to represent the
- A single strait line (---)
represents a single bond
- Two parallel strait lines (==)
represent double bonds
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Last Updated: March 11, 2004