1. The Atom

2. What’s Inside an Atom

3. The Nucleus
The nucleus is the small dense, positively charged center of the atom. It contains most of the atom's mass.

4. The Proton Proton Profile Charge: positive Mass: 1 amu
Location: nucleus

5. The Neutron Neutron Profile Charge: Neutral Mass: 1 amu
Location: Nucleus

6. The Electron Electron Profile Charge: negative Mass: almost zero
Location: electron cloud (outside the nucleus)

7. The Atomic Number
The atomic number is the number of protons in the nucleus of an atom
The number of protons determines the element
Atomic Number

8. Mass Number
The mass number is the sum of the protons and neutrons in an atom (measured in amu)
Mass Number

9. Isotopes
Isotopes are atoms that have the same number of protons, but have different numbers of neutrons.

10. Calculating the number of Neutrons in an Atom.
How many neutrons are in a Carbon atom with an atomic weight of 14.
Atomic weight is the number of protons and neutrons.
The atomic number is the number of protons………….so,
14 – 6 = 8 neutrons

11. Average Atomic Mass
The average atomic mass is the weighted average of the masses of all the naturally occurring isotopes of an element.

12. Calculating the Average Atomic Mass
What is the average atomic mass of Chlorine;
if 75% is chlorine-35, and
25% is chlorine-37?
(35 X .75) + (37 X .25) =
(26.25) (9.25) = amu