Ions

Valence Shell The outer ring of an atom filled with valence electrons

Octet Rule Atoms are most stable when they have a full octet, or 8 valence electrons Some atoms are exceptions – they are most stable with only 2 electrons (H, He, Li, Be, B) Noble gases are all stable

Anions Some atoms GAIN electrons to become stable Negative charge

Anion Charge If chlorine gains an electron… P: 17+ E: 18- Overall charge: -1

Cations Some atoms LOSE electrons to become stable Positive charge

Cation Charge If sodium loses an electron… P: 11+ E: 10- Overall charge: +1

Bohr Model K Mg O F Ne Complete the following Bohr models. Determine if the element needs to lose or gain electrons to become stable (remember the levels!) K Mg O F Ne

Patterns with valence electrons What patterns do you notice based on your Bohr models? The number of valence electrons matches the group number

Oxidation Number The number of electrons needed to gain or lose for stability equals the oxidation number, or charge Also a pattern by group Label these representative groups: Group 1: +1 Group 5: -3 Group 2: +2 Group 6: -2 Group 3: +3 Group 7: -1 Group 4: none Group 8: none

Ion P, N, E Symbol Protons Neutrons Electrons Charge K+1 19 20 18 +1 Be+2 Al+3 P-3 S-2 I-1 Xe

Lewis Dot Structures Used to represent the number of valence electrons Can be used later in symbolizing chemical bonds between atoms

Checkpoint Why do atoms gain or lose valence electrons? Describe the change in an atom that has a +3 charge. Why is it positive? What does the “3” mean? When atoms gain or lose electrons, where do they go? Define the octet rule. Describe the patterns seen on the periodic table related to electrons.