Homework from last time. Your Homework Question: What is the difference between an Atom and an Element? Out of 3 marks

Transcription

1 Homework from last time Your Homework Question: What is the difference between an Atom and an Element? Out of 3 marks

2 How is this possible?

3 Bohr Models S Objective: Assemble or draw Bohr atomic models for the first 18 elements and group them according to the number of outer shell electrons.

4 Bohr models? I thought we don t use the planetary model anymore? It is true that we don t use the planetary model to describe the atomic model anymore but for low atomic number elements Bohr s model works wonderfully well in describing the arrangement of the atom It describes the electron structure of elements It tells us the number of protons, neutrons an atom has in its nucleus It gives us the number of valence electrons an atom of an element has

5 Quick recap Subatomic Particle Symbol and Charge Mass Location Proton p + 1 amu Nucleus Neutron n 0 1 amu Nucleus Electron e times lighter than a proton & neutron! Electron orbitals (outside the nucleus) Bohr Diagrams are meant to show how many electrons exist for an atom and where they are! The reactivity of the atom depends on electrons!

6 Valence Shells Valence shells are the most outer ring from the nucleus in an atom Valence shells are filled with valence electrons These are the special electrons that allow atoms to react and form substances

7 What does reactivity mean? Reactivity is something you will study a lot of next year in science class but it all boils down to how the electrons act when they are excited Excited electrons have the ability to jump to different electron shells and give off energy in the form of light. Bohr studied a lot on this subject and that is why we still use his knowledge today much of it is still true and useful! Colour green red purple lavender yellow Element copper strontium potassium Lithium sodium

8 How to draw Bohr models Determine the number of subatomic particles How many electrons, protons, and neutrons exist for this element Draw the nucleus as a circle Inside the circle indicate how many protons and neutrons exist (use the symbols). The number of protons equals the atomic number The number of neutrons equals the atomic mass (rounded) minus the atomic number Draw a circle around the nucleus to indicate the first energy level (the first electron shell) Fill this with the maximum amount of electrons allowed If necessary, draw additional, bigger circles around the nucleus to represent more energy levels and fill with the maximum amount of electrons

9 Rules for energy levels (electron shells) You are only responsible for drawing Bohr models up to 3 energy levels (3 circles around the nucleus) The first energy level can have a maximum of 2 electrons (2e) The second can have a max of 8 electrons (8e) The third can have a max of 8 electrons (8e) Rules get pretty fuzzy after that as the Bohr model starts to fall apart when we start adding fourth and fifth energy levels We always start draw Bohr diagrams from inside outside

10 Some practice 6 C Valence Electron amount:

11 Some practice 16 S Valence Electron amount:

12 Some practice 11 Na Valence Electron amount:

13 Some practice Valence Electron amount:

14 Some practice Valence Electron amount:

15 Our Objective Homework time! Draw the Bohr Diagram for Neon. What do you notice about the number of valence electrons? Definition 27 can be done now! Outcome questions due Friday and quiz coming up next week! Objective: Assemble or draw Bohr atomic models for the first 18 elements and group them according to the number of outer shell electrons.