Bohr-Rutherford Diagrams for Atoms

13p14n

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.

Trends in the Periodic TableTrends in the Periodic Table

Period 1 -Period 1 -1 orbital1 orbital Period 2 -Period 2 -

2 orbitals2 orbitalsPeriod 3 -Period 3 -3 orbitals3 orbitals Period 4 -Period 4 -

4 orbitals4 orbitals

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.

Examples of Bohr-Rutherford diagram:

Lithium (Li)Atomic Number=3

# protons = 3

# electrons = 3

# neutrons = 4

Atomic mass = 7

3p4n

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.

Example of Bohr-Rutherford diagram:

Aluminum (Al)Atomic Number = 13

# protons = 13

# electrons = 13

# neutrons = 14

Atomic mass = 27

13p14n

Bohr-Rutherford diagram of the first twenty elements:

• Draw the Bohr-Rutherford diagrams of the first TWENTY elements on the chart provided.

• The electrons in the outer orbital are called VALENCE ELECTRONS

3p4n

• How many valence electrons does lithium have?

• Just 1!

Trends in the Periodic TableTrends in the Periodic TableGroup 1Group 11 valence e1 valence e--

Group 2:Group 2:2 valence e2 valence e--

Group 13:Group 13:3 valence e3 valence e--

Group 15Group 155 valence e5 valence e--

Group 16Group 166 valence e6 valence e--

Group 17Group 177 valence e7 valence e--

Group 18Group 188 valence e8 valence e--

(2 for He)(2 for He)

Group 14:Group 14: 4 valence e4 valence e--