1. Atomic Structure and the Periodic Table
Protons, Neutrons, Electrons and What Those Numbers Mean

2. When classifying elements on the Periodic Table, 2 different methods are used:
The Atomic Number of an element
The Atomic Mass of an element

3. What is Atomic Mass? The average mass of an atom of an element.
The sum of the number of protons added to the sum of the number of neutrons.

4. Find the atomic mass of the following:
Lithium
Element number 30 Ar
Scandium
Element number 9 Cl

5. Atomic Number The number of protons in the nucleus of an atom
Also tells us the number of electrons in an atom.

6. Find the atomic number of the following:
Beryllium Ne
Tin As
Magnesium W

8. On the Periodic Table.. Atomic number is written on the top left.
In the middle is the Chemical Symbol (letter(s) that represent the type of atom)
Atomic mass is written on the bottom

9. How to use the numbers…
The number of subatomic particles in an atom can be determined by knowing the atomic number and atomic mass, and that there is an important difference in these numbers.

10. How to find the 3 subatomic particles:
Number of protons is equal to the atomic number
Number of electrons is equal to the atomic number
Side note: In a neutral atom, the electrons are always equal to the protons.
Number of neutrons is calculated by subtracting the atomic number from the atomic mass.

11. Example Atomic number = 11 Atomic mass = 22.990 Protons = 11
Electrons = 11
Neutrons = 23 ( rounded up) – 11 = 12

12. Let’s try another… Atomic number = Atomic Mass = Protons = Electrons =
Neutrons =