7-1 Lewis Dot Diagrams

Dot Diagrams . : : . : . . : . : . : : . : : . . : . : . : : . : : [x] s2p6 H . He : s2 s2p1 s2p2 s2p3 s2p4 s2p5 C : . : . N X . X : . : . O Be : : . F : Ne : . X Al . : . X : . : X : . X X : X : +4 -4 +1 +2 +3 -3 -2 -1 [x] [x] [x] [:x:] : [:x:] : [:x:] : Ion formation: Loss (oxidation) or gain (reduction) of electrons

[ ] [ ] A1. NaI I Na Does it start with a metal? Yes, so it is Ionic. Use brackets & charges. (-) ions have 8 dots, (+) ions have 0 dots. -1 [ +1 ] [ ] Na I

Rules for Ionic Combos If the combo starts with a metal, assume it is all charged and use brackets. Put opposite charges next to each other and similar charges away. Metal ions always are positive, non-metals are negative. Determine the charges by columns in the periodic table. Negative (-) ions will end up with 8 electron dots, positive (+) ions have 0.

[ ] [ ] A2. BaO O Ba Does it start with a metal? Yes, so it is Ionic. Use brackets & charges. (-) ions have 8 dots, (+) ions have 0 dots. -2 [ +2 ] [ ] Ba O

[ ] [ ] [ ] A3. CaF2 F F Ca Does it start with a metal? Yes, so it is Ionic. Use brackets & charges. (-) ions have 8 dots, (+) ions have 0 dots. -1 -1 [ ] [ +2 ] [ ] F Ca F

[ ] [ ] [ ] [ ] A4. K3P K K P K Does it start with a metal? Yes, so it is Ionic. Use brackets & charges. (-) ions have 8 dots, (+) ions have 0 dots. [ +1 ] [ -3 ] [ +1 ] K P K [ ] +1 K

B1. H2 H H If it doesn’t start with a metal, it’s covalent. Count the number of total valence electrons. Each H has 1 electron for a total of 2. Place 2 dots between each adjacent atoms to bond them. H H

Rules for Covalent Combos Make sure you have the right number of dots or you will never get the right answer. Electron dots will always be in pairs. Every non-metal but hydrogen must have 8 electron dots to be stable. Hydrogen only needs 2 electron dots to be stable. If you are short, move pairs in between to make double or triple bonds

B2. Cl2 Cl Cl If it doesn’t start with a metal, it’s covalent. Count the number of total valence electrons. Each Cl has 7 electron for a total of 14. Place 2 dots between each adjacent atoms to bond them. Place the remaining dots in pairs symmetrically around the 4 sides of each atom. Cl Cl Each atom has a complete octet (8).

H S H B3. H2S If it doesn’t start with a metal, it’s covalent. Count the number of total valence electrons. Each H has 1 electron for a total of 2. A S atom has 6. The total is 8 dots. Place 2 dots between each adjacent atoms to bond them. Hydrogens only need 2 dots, other non-metals need 8. Place the remaining dots in pairs symmetrically around the 4 sides of each atom. H S H Each atom has an octet (8) or complete valence shell.

B4. OF2 F O F If it doesn’t start with a metal, it’s covalent. Count the number of total valence electrons. Each F has 7 electrons for a total of 14. An O atom has 6. The total is 20 dots. Place 2 dots between each adjacent atoms to bond them. Place the remaining dots in pairs symmetrically around the 4 sides of each atom. F O F Each atom has a complete octet (8).

H N H H B5. NH3 If it doesn’t start with a metal, it’s covalent. Count the number of total valence electrons. Each H has 1 electron for a total of 3. An N atom has 5. The total is 8 dots. The 1st atom is usually central. Place 2 dots between each adjacent atoms to bond them. H only requires 2 dots. Other atoms require 8 dots. H N H H

Cl P Cl Cl B6. PCl3 If it doesn’t start with a metal, it’s covalent. Count the number of total valence electrons. Each Cl has 7 electrons for a total of 21. A P atom has 5. The total is 26 dots. The 1st atom is usually central. Place 2 dots between each adjacent atoms to bond them. H only requires 2 dots. Other atoms require 8 dots. Place the remaining dots in pairs symmetrically around the 4 sides of each atom. Cl P Cl Cl

B7. CH4 H H C H H If it doesn’t start with a metal, it’s covalent. Count the number of total valence electrons. Each H has 1 electron for a total of 4. An C atom has 4. The total is 8 dots. Place 2 dots between each adjacent atoms to bond them. H only requires 2 dots. Other atoms require 8 dots. H H C H H

I H C H H B8. CH3I If it doesn’t start with a metal, it’s covalent. Count the number of total valence electrons. Each H has 1 electron for a total of 3. An C atom has 4. An iodine has 7 dots. The total is 14 dots. The 1st atom is usually central. Place 2 dots between each adjacent atoms to bond them. H only requires 2 dots. Other atoms require 8 dots. Place the remaining dots in pairs symmetrically around the 4 sides of each atom. I H C H H

C1. O2 O O Each O has 6 electron for a total of 12 dots. Place 2 dots between each adjacent atoms to bond them. Place the remaining dots in pairs symmetrically around the 4 sides of each atom. H only requires 2 dots. Other atoms require 8 dots. If you are short, move pairs in between to make double or triple bonds O O Now each atom has an octet (8) of valence electrons.

C2. CO2 Each O has 6 electron for a subtotal of 12. The C has 4 for a grand total of 16 dots. Place 2 dots between each adjacent atoms to bond them. Place the remaining dots in pairs symmetrically around the 4 sides of each atom. H only requires 2 dots. Other atoms require 8 dots. If you are short, move pairs in between to make double or triple bonds O C O Double bonds give each atom 8 electrons.

C3. C2H2 H C H C A triple bond in needed so each atom has 8 electrons. Each C has 4 electron for a subtotal of 8. Each H has 1 for a grand total of 10 dots. The 1st atom is usually central. Place 2 dots between each adjacent atoms to bond them. Place the remaining dots in pairs symmetrically around the 4 sides of each atom. H only requires 2 dots. Other atoms require 8 dots. If you are short, move pairs in between to make double or triple bonds H C C H A triple bond in needed so each atom has 8 electrons.

D1. H3O+ Each H has 1 electron for a subtotal of 3. An O has 6. A positive charge means 1 electron is missing. (Negative charge indicates extra electrons.) The total is 8 dots. O has to be central. H’s can only make 1 bond. Place 2 dots between each adjacent atoms to bond them. H only requires 2 dots. Other atoms require 8 dots. Place in brackets & label the charge. [ ] H O H H +1

D2. NH4+ Each H has 1 electron for a subtotal of 4. An N has 5. A positive charge means 1 electron is missing. (Negative charge indicates extra electrons.) The total is 8 dots. The 1st atom is usually central. Place 2 dots between each adjacent atoms to bond them. H only requires 2 dots. Other atoms require 8 dots. Place in brackets & label the charge. [ ] H +1 H N H H

[ ] H O D3. OH- The H has 1 electron. An O has 6. A negative charge means there is 1 extra electron. (Positive charge indicates missing electrons.) The total is 8 dots. Place 2 dots between each adjacent atoms to bond them. H only requires 2 dots. Other atoms require 8 dots. Place the remaining dots in pairs symmetrically around the 4 sides of each atom. Place in brackets & label the charge. -1 [ ] H O

D4. PO4-3 Each O has 6 electrons for 24. A P atom has 5. A negative 3 charge means 3 extra electrons. (Negative charge indicates extra electrons.) The total is 32 dots. The 1st atom is usually central. Place 2 dots between each adjacent atoms to bond them. H only requires 2 dots. Other atoms require 8 dots. Place the remaining dots in pairs symmetrically around the 4 sides of each atom. Place in brackets & label the charge. [ ] O -3 O P O O

Review Examples E1 – AlCl3 E4 – OCl2 E8 – HCN Get out your periodic table & dot diagram handout.

[ ] [ ] [ ] [ ] E1. AlCl3 Cl Al Cl Cl Does it start with a metal? Yes, so it is Ionic. Use brackets & charges. (-) ions have 8 dots, (+) ions have 0 dots. +3 -1 [ ] [ ] [ ] Cl Al Cl Done! -1 [ ] Cl -1

E4. OCl2 Cl O Cl If it doesn’t start with a metal, it’s covalent. Count the number of total valence electrons. Each Cl has 7 electrons for a total of 14. An O atom has 6. The total is 20 dots. Place 2 dots between each adjacent atoms to bond them. Place the remaining dots in pairs symmetrically around the 4 sides of each atom. Cl O Cl Each atom has a complete octet (8).

E8. HCN H is a non-metal so this is covalent. Add up the valence electron dots for each atom. The C has 4 electrons. The N has 5 dots. The H has 1 for a grand total of 10 dots. The 1st atom is usually central, but H can only make 1 bond. The C is then central. Place 2 dots between each adjacent atoms to bond them. Place the remaining dots in pairs symmetrically around the 4 sides of each atom. H only requires 2 dots. Other atoms require 8 dots. If you are short, move pairs in between to make double or triple bonds H C N A triple bond in needed so the C & N each have 8 electrons.

Dot Diagrams Quiz Formula Ionic or Covalent? (1st element?) SBr2 SrF2 SiO2