7-1 Lewis Dot Diagrams. Dot Diagrams [x] [:x:] : : : :.. O : : : : Ne : :.. X H. X. Be : X : X :. Al. : C :.... X : :... N... : X : :. F : X : : : : :

7-1 Lewis Dot Diagrams

Dot Diagrams

[x] [:x:]:

:

:: . .O

::: :Ne

: :. .X

H.

X. Be:X:

X: .

Al.

: C:. .

. .X:

:. ..N

. . .

:X

: :.F:

X

::: ::: .X

:He:

[:x:]

::[:x:]:

:[x] [x]+4-4

+1 +2 +3 -3 -2 -1

s1

s2 s2p1 s2p2 s2p3 s2p4 s2p5

s2p6

Ion formation: Loss (oxidation) or gain (reduction) of electrons

A1. NaI

• Does it start with a metal? • Yes, so it is Ionic.• Use brackets & charges.• (-) ions have 8 dots, (+) ions have 0 dots.

Na[ ]+1

I[ ]-1

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


Ba[ ]+2

O[ ]-2

A3. CaF2


Ca[ ]+2

F[ ]-1-1

][F

A4. K3P


P[ ] K[ ]+1+1

][K][ K

+1

-3

B1. H2

• 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• 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).

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


H S H

Each atom has an octet (8) or complete valence shell.

B4. OF2• 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



F O F


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 HH

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 ClCl

B7. CH4• 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 C HH

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.

H C HH

I

C1. O2• 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

C O

Double bonds give each atom 8 electrons.

O

H

C3. C2H2 • 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

C C

A triple bond in needed so each atom has 8 electrons.

H

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 HH[ ]+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 N HH[ ]

+1H

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.

H O[ ]-1

OO

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 P[ ]-3

Review Examples

• E1 – AlCl3• E4 – OCl2• E8 – HCN

• Get out your periodic table & dot diagram handout.

Cl

E1. AlCl3


Al[ ] Cl[ ]-1

-1][

][Cl-1

+3

Done!

Cl

E4. OCl2• 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



Cl O


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

C N

A triple bond in needed so the C & N each have 8 electrons.

H

Dot Diagrams Quiz

Formula Ionic or Covalent?

(1st element?)

Dot Diagram

SBr2

SrF2

SiO2

Documents

7-1 Lewis Dot Diagrams. Dot Diagrams [x] [:x:] : : : :.. O : : : : Ne : :.. X H. X. Be : X : X :. Al. : C :.... X : :... N... : X : :. F : X : : : : :