1. ATOMS
CHEM-IS-TRY

2. Atoms are the basic building components of all matter.
Atoms are composed of three types of particles: protons, neutrons, and electrons.
Protons and neutrons reside in the dense, central, positively-charged nucleus of an atom.

3. Electrons orbit the nucleus and are located in the region outside the nucleus.

4. The mass of a single proton, for example, is approximately 1
The mass of a single proton, for example, is approximately 1.67 x 10e-27 kg. The mass of an electron is approximately 9.11 x 10e-31 kg.
Mass of a neutron
x kg

5. Protons have a positive charge (+)
Neutrons are neutral with no charge.
Electrons have a negative electric charge (-).
In a neutral atom, the number of protons always equals the number of electrons.

6. # protons = atomic number
# electrons in a neutral atom = number of protons
# of neutrons = the difference between the mass number and the atomic number
mass number = protons + neutrons

8. Arrangement of the electrons
The maximum number of electron in the first energy level = 2 electrons
The maximum number of electron in the second energy level = 8 electrons
The maximum number of electron in the third energy level = 18 electrons
The maximum number of electron in the fourth energy level 32 electrons
The maximum number of electron in the fifth energy = 50 electrons
The maximum number of electron in the sixth energy level = 72 electrons
The maximum number of electron in the seventh energy level = 98 electrons