1. Bohr-Rutherford Diagrams for Atoms
13p
14n

2. Bohr stated that…
Electrons move around the nucleus in nearly spherical paths called orbitals, like planets around the Sun.
The number of orbitals for an element is the period number.
The maximum number of electrons in an orbital is the number of the elements in the period.

3. Trends in the Periodic Table
1 orbital
Period 2 -
2 orbitals
Period 3 -
3 orbitals
Period 4 -
4 orbitals

4. Bohr-Rutherford Diagram
Bohr-Rutherford diagrams represent the arrangement of protons, neutrons, and electrons in an element.
In these diagrams, the number of protons and neutrons are written in the centre to represent the nucleus of the atom.
Circles are drawn around the nucleus to represent orbitals, and electrons are shown in these orbitals.

5. Examples of Bohr-Rutherford diagram:
Lithium (Li)
Atomic Number=3
Atomic mass = 7 3p 4n
# protons = 3
# electrons = 3
# neutrons = 4

6. Rules for adding electrons
The first orbital can hold up to 2 electrons.
The second and third orbital can hold up to 8 electrons.
When filling orbitals with electrons, place the first 4 electrons in a compass point before pairing.

7. Example of Bohr-Rutherford diagram:
Aluminum (Al)
Atomic Number = 13
Atomic mass = 27
13p
14n
# protons = 13
# electrons = 13
# neutrons = 14

8. Bohr-Rutherford diagram of the first twenty elements:
The electrons in the outer orbital are called VALENCE ELECTRONS 3p 4n
How many valence electrons does lithium have?
Just 1!
Draw the Bohr-Rutherford diagrams of the first TWENTY elements on the chart provided.

9. Trends in the Periodic Table
Group 1
1 valence e-
Group 13:
3 valence e-
Group 15
5 valence e-
Group 17
7 valence e-
Group 18
8 valence e-
(2 for He)
Group 16
6 valence e-
Group 2:
2 valence e-
Group 14:
4 valence e-