Chemistry– 12/13/2019 Objectives (I can…) Bell Ringer – Review 3.2 Describe the early models of the atom and construct Bohr Models of the atom. Bell Ringer – Review Determine the number of electrons, protons, and neutrons in potassium Homework: Complete Bohr Model Worksheet Read chapter 5 and complete study guide

Bell ringer Determine the number of p+, e-, and n0 in the potassium 39 19 #p+ = 19 #e - = 19 #n0 = 39 – 19 = 20 K

Constructing Bohr Models Step 1: Determine the number of p+, e-, and n0 in the atom. Example: Lithium #p+ = 3 #e - = 3 #n0 = 4

Constructing Bohr Models Step 2: Place the p+ and e- in a center nucleus Step 3: Place electrons in orbits around the nucleus. Place electrons in orbit around nucleus. Fill each level with the appropriate number of electrons Maximum electrons in each level 1st level: 2 2nd level: 8 3rd level: 18 4th level: 18 5th level: 32 #p+ = 3 #n0 = 4

Constructing Bohr Models Step 2: Place the p+ and e- in a center nucleus Step 3: Place electrons in orbits around the nucleus. Place electrons in orbit around nucleus. Fill each level with the appropriate number of electrons 3 p+ 4 n0 2e– 1e– #p+ = 3 #n0 = 4

Constructing Bohr Models Bohr models are limited in scope, in larger atoms electrons will begin filling the next electron level before completing the earlier level. For this reason, you will not be expected to construct any Bohr models with an atomic number greater than 20. We will revisit Bohr models later

Constructing Bohr Models EXAMPLE: Beryllium

Constructing Bohr Models EXAMPLE: Potassium

Constructing Dot Diagrams Dot diagram – A diagram to represent electrons in the outer energy level of an atom; uses the element symbol and dots

Constructing Dot Diagrams Dot diagram – A diagram to represent electrons in the outer energy level of an atom; uses the element symbol and dots Example: Lithium Bohr Model Dot Diagram Li #p+ = 3 #n0 = 4

Constructing Dot Diagrams Beryllium Potassium

Atomic Structure Isotopes – Atoms with the same number of protons but different number of neutrons. Bohr Models of Isotopes Carbon-12 Carbon-14

Atomic Structure Isotopes – Atoms with the same number of protons but different number of neutrons. Dot Diagrams Carbon-12 Carbon-14

Isotope Practice Problems Construct Bohr Models and Dot Diagrams of the following Isotopes Lithium-6 Lithium-7 #p+ = #p+ = #e- = #e- = #no = #no =

Isotope Practice Problems Uranium-238 Uranium-235 #p+ = #p+ = #e- = #e- = #no = #no =

Constructing Bohr Models and Dot Diagrams More examples or worksheet?