Download Chemistry Notes

NOTES: ATOMS AND CHEMISTRY
I. The Chemistry of matter
A. All matter in the universe is composed of atoms.
B. Parts of an atom
1. Electron Shell – The outer part of an atom. This is where
the electrons are found.
a) Electrons – Negatively charged particles found in the
electron shell. Electrons orbit the nucleus.
2. Nucleus – The center of the atom. Composed of Protons
and Neutrons.
a) Proton – Positively charged particles.
b) Neutron – Neutral particles.
C. For the Elements, the number of electrons in an atom is
equal to the number of Protons. This is called the Atomic
Number.

Different Atoms have different numbers of Protons,
Neutrons and Electrons. These are called Elements.
D. Elements – Matter composed of the same type of atoms.
Example: Gold is an element; it is made of gold atoms.

There are 93 natural elements found on Earth.
E. Compounds – Matter composed of 2 or more elements
chemically combined. Example: H20 (water)

Compounds are held together by atomic bonds, there are
2 types:
F.
Ionic Bond – A weak bond formed by two differently charged
Ions sticking together.
a) Ion – An atom which has gained or lost electrons.
Example: Salt (NaCl)
Sodium: Na (#11)
Chlorine: Cl (#17)
11P
17P
11N
17N
G. Covalent Bond – A very strong bond caused by the sharing of
electrons between atoms. This bond requires lots of energy to
make and to break.
Example: Water H2O
Hydrogen: H (#1)
1P
Oxygen: O (#8)
8P
8N
Hydrogen: H (#1)
1P