Valence Electrons & Bohr Diagrams

Learning Goal Today’s learning goal is for students to: For students to recall knowledge of the atomic structure & valence electrons For students to develop their knowledge of Bohr Rutherford Diagrams For students to apply their knowledge of valence electrons to drawing Lewis Dot Diagrams

RECALL: Atomic Structure Atoms have a nucleus that contains Protons and Neutrons Electrons are contained in shells that surround the nucleus An atom is made of mostly empty space Protons have a positive charge Electrons have a negative charge Neutrons are Neutral

Valence Electrons Electron Shell Number of Electrons 1 2 8 3 4 18 5 6 32 7 Each electron shell can hold a certain number of electrons Electron shells are filled from the inside out Noble Gases have full outer electron shells All other elements have partially filled outer electron shells

Noble Gas Stability Noble gases are usually unreactive This is because they have full valence shells An element with a full valence shell is a happy element  For two atoms to join together atoms must gain, lose or share electrons Elements with full valence shells do not easily gain or lose electrons

Noble Gas Stability Atoms want to gain stability Atoms will try to gain or lose electrons to have a full valence shell Metals try to lose electrons Non-Metals try to gain electrons

Bohr-Rutherford Diagrams

Two Important Scientists The Bohr atom model and the Rutherford atom model of the atom were put together to come up with the Bohr-Rutherford model of the atom The Bohr-Rutherford model allows the subatomic particles to be visible to the eye

Four Steps To Draw A Bohr-Rutherford Diagram Draw the nucleus Write P – Number of Protons & N - Number of Neutrons in the middle of the nucleus Nucleus

3. Follow the octet rule The octet rule is a chemical rule of thumb that says how electrons should be arranged in each orbital when drawing Bohr- Rutherford Diagrams Where: The 1st orbit has a max of 2 electrons The 2nd orbit has a max of 8 electrons The 3rd orbit has a max of 8 electrons

4. Fill in # Electrons in orbitals Na - Sodium Remember the Octet Rule 2, 8, & 8 When filling in electrons, pair them up electrons leaving lone electrons to the end Example: Sodium (Na) Has Atomic # 11 Has Atomic Mass of 23 P – E – N - ● 11 P 12 N ●

4. Fill in # Electrons in orbitals ● Draw electron orbitals as needed Use dots to represent the number of electrons each element has The electrons on the most outside orbital are the Valence Electrons ● ● ● ● ● 11 P 12 N ● ● ● ● ●

Example

Worksheet Time! Bohr Rutherford Diagrams!

Lewis Dot Structures Sometimes it can take a while to draw every single electron in a diagram – as in Bohr Rutherford Diagrams So Gilbert Newton Lewis, an American physical, came up with an idea to simplify drawing atomic structures We now use his Lewis dot structures to show how many valence electrons an element has These dots can also represent bonds when put with another element