Chemical BondsUnit 6

Chapter 6

IONIC

COVALENT

METALLIC

I. Why do atoms bond?A. Atoms bond in order to become stable

B. Electron configurations of the noble gases are stable.

1. Helium is stable with 2 valence e-.2. All others are stable with 8

valence e-.

C. Atoms of unstable electron configurations will gain, lose, or share electrons to become stable like a noble gas.

not stable stable

not stable stable

II. Electron Dot Notation

A. Only valence electrons are used in bonding

B. Electron dot notation highlights the valence electrons

Al Ca F Cs

12 3 4 5 6 7

8

Representative Group Valence Electrons

How to draw the electron dot notation of an atom:

Step 1: Write the chemical symbol

Step 2: Imagine a box around it

Step 3: Draw a dot for each valence electron Dots only go on the SIDES of the box

Rule: One dot per side before you double up

As

As

As

As AsYES!

Now you try some.

Li Cl Ne

Sr C Mg

Pb N I

What would happen if sodium and chlorine bump into each other?

An electron would transfer from the Na atom to the Cl atom so that each atom would become a stable ion.

Net charge +1 Net charge -1

III. Ionic BondsA. Metal – Nonmetal

B. Electrons are transferred from the metal to the nonmetal

C. Ions are produced

D. Ion attraction makes the bond

(+) (-) Na+1 Cl-1

E. A Crystal is formed

Ca I Ca I

Let’s Practice!

K Br

Before bonding After Bonding Chemical Formula

K Br KBr

I ICaI2

+1 -1

+2-1

-1

Ion net charge = zero!

Ion net charge = zero!

A. Nonmetal – Nonmetal

B. Electrons are shared

C. Molecules are produced

D. Sharing makes the bond (tug-o-war)

F F or F F

IV. Covalent Bonds

2 Shared electrons 2 Shared electrons

E. Can have double and triple bonds

Double: O O or O O 4 Shared electrons 4 Shared electrons

Triple: N N or N N 6 Shared electrons 6 Shared electrons

(a stronger bond)

(the strongest bond)

F. Diatomic elements are formed as follows:

H2 N2 O2 F2

Cl2 Br2 I2

BrINClHOF

Let’s Practice!Before bonding After Bonding Chemical Formula

C H

H

H

H HH C H H

CH4

All atoms are stable!

Now you try some.

1. N and F

2. H and O

3. Diagram the molecule C2H6O

Answer to #1:

N F

F

F

FF

F N F NF3

before after formula

Answer to #2:

HO

H

H OH

H2O

before after formula

Answer to #3: C2H6O

O HC

H

H

H

H

C

H

C

H

H

H

O

H

C

H

H

or

A. metal – metal

B. Electrons are pushed from atom to atom.

C. Electrons are free to move among the metal atoms allowing metals to conduct electricity. (see picture below)

D. A mixture of metals is called an Alloy.

V. Metallic Bonds

A. Formula Writing1. Cation first, anion second

Ca+2 Cl-1

2. Net charge must equal zero

Ca+2 Cl-1 Cl-1 = zero (It takes 2 chloride ions to stabilize the Ca)

3. Write the formula: CaCl2

VI. Ionic Binary Chemicals

B. Naming1. The metal ion has the same name as the metal atom.

Ca+2 is named calciumK+1 is named potassium

2. Some metals form more than one ion. These metals require a roman numeralafter their name to indicate which ion isin the chemical formula.

Fe+2 is named iron (II)Fe+3 is named iron (III)

NO roman numeral in the name, elementonly produces one common ion.

Roman numeral is necessary, elementcontains more than one common ion.

3. The nonmetal ion will end with the suffix -ide.

Examples:

S-2 is named sulfideF-1 is named fluoride

O-2 is named oxideP-3 is named phosphideN-3 is named nitride

A. Formula Writing1. Follow the ionic rules.

2. Ternary chemicals contain a polyatomic ion.

polyatomic ion- a group of covalently

bonded atoms that act as a single ion

examples: CO3-2 NH4

+1

VII. Ionic Ternary Chemicals

3. RULE: If more than one polyatomic ion is needed to write the

chemical formula use parenthesis.

example: Ca+2 NO3-1

NO3-1

CaNO32

zeronet charge

Ca(NO3)2

YES, two NO3-1 ions!(looks like we have 32 oxygen atoms)

B. Naming 1. Follow the ionic rules.

2. Examples:

Al(OH)3 is named aluminum hydroxide

Cu(NO3)2 is named copper (II) nitrate

K2CO3 is named potassium carbonate

A. Greek prefixes are used to identify the number of each element in a covalent compound.

mono = 1di = 2tri = 3tetra = 4penta = 5hexa = 6hepta = 7

VIII. Covalent Chemicals

B. Rule: mono- is never used for the first

element in the compound.

C. Sometimes the last letter of the prefix is dropped if the name of the element starts with a vowel.

D. Examples:

CO2 is named carbon dioxideCO is named carbon monoxidedinitrogen monoxide is written as N2O