1. Atomic Structure
SOL 6.4

2. Parts of an Atom
Protons
Neutrons
Electron

3. Protons Have a positive (+) charge Are located in the nucleus
Give an atom its identity
Are equal to the atomic number

4. Lithium has an atomic number 3. Therefore, Lithium has 3 protons.
Another way of phrasing this fact is, any atom with the atomic number 3 MUST be Lithium.

5. Neutrons Have NO charge- they are neutral Are located in the nucleus
Remember the ‘NEWS’ about atoms-Neutral neutrons are located in the nucleus!

6. The mass number of an atom is calculated by adding protons + neutrons
The mass number of an atom is calculated by adding protons + neutrons. Atomic mass is an average of the masses of all the atoms of that element.
The atom to the left has 3 protons and 3 neutrons.
3 + 3 = 6
The mass number of this atom is 6.

7. Isotopes are the SAME element, but have different numbers of NEUTRONS and therefore different mass numbers.

8. Electrons Are the smallest, lightest particle
Are located outside the nucleus in the elctron cloud
Have a negative charge
Are equal to the number of protons in a neutral atom
“I don’t care”

9. Models of the Atom
Bohr model
Electron cloud model

10. What is the atomic number?
Let’s Practice!
What is the atomic number?
What is the mass?
How many protons?
How many neutrons?
How many electrons? 9 17

11. Element
An element is the simplest form of matter. It is made up of only ONE type of atom.
An element ALWAYS has the same number of protons and same atomic number. However, it may have different numbers of neutrons and different masses (isotopes).
Elements are represented by chemical symbols. Chemical symbols are ALWAYS Capitalized (one letter) or Capital lower case (two letters).