bonding

BONDING

K Warne

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Periodic Table Test

Give the names of

the following

elements:

1. Na

2. S

3. N

4. C

5. Ca

6. Cu

7. F

8. Ne

9. Pt

10. Mg

Give the SYMBOL

of the following

elements:

1. Iron

2. Chrome

3. Lead

4. Mercury

5. Gold

6. Platinum

7. Phosphorus

8. Uranium

9. Nickel

10. Silicon

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Bonding

O

H2O

O

H2O

OO

Two hydrogen molecules and one oxygen molecule react to form two water

molecules.


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HH

Reactions

H2 + Cl2 2HCl

3H2 + N2 2 NH3

H H Cl Cl ClH ClH

H HN N N

HH

N

H HH

H

H H

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Covalent bond

A shared PAIR of electrons. Electrons from one atom are attracted strongly by the

nucleus of another atom.

Formed between non metals. (Attract electrons strongly!)

Pure covalent bonds have EQUAL SHARING of the

electrons.

In diatomic Molecules; H2, O2, F2, Cl2, Br2, I2, N2,

H H

In covalent substances the electrons are strongly held in the bonds

and so the substance will NOT conduct electricity.

HH •x

Couper structure





Covalent Molecules – Bohr Diagrams

H2, O2, F2, Cl2, Br2, N2, H2O, NH3, CH4

O O

p=8

n=8

p=8

n=8

O=OO2

Two shared

electron pairs

Two shared

electron pairs

form a DOUBLE

covalent bond!





F F

Fluorine F2

p=9

n=10

p=9

n=10

F-F





Diatomic Molecules

O2 indicates that two oxygen atoms are BONDED

together into an oxygen molecule.

2O just indicates that you have two oxygen atoms.

O2 2OWhat is the difference?

O O O O

O2=Bonded

oxygen molecule

NOT bonded = 2O





Covalent Molecules CH4

H

H

C

C

H

methane

CH

H

H

H

Since carbon has 4

valence electrons 4

hydrogens are needed

4 shared pairs = 4

covalent bonds





x

x

Covalent Molecules N2

N

N

N Nxx x

3 shared pairs is a

triple bond

One lone or

unbonded pair

each

NN

A triple covalent bond

is very strong so

nitrogen is VERY

UNREACTIVE!

~70 % of the

atmosphere is nitrogen

– it does not react with

almost anything!

Nitrogen is used in

crisp packets to keep

the crisps fresh

because it does NOT

react with them.





Ionic Bonding

Formed when there is a ………….

of …………………...

Formed between ………….. and ………………….

Metals …………………….. and

become ……………………... ions -CATIONS.

Non metals …………………... and become …………………………. ions - ANIONS.

…………………………… between oppositely charged ions bonds the ions together.

Na.

..

:Cl: -

..Na

+

.

:Cl:..

..

Na.

+ : Cl: --> [Na]+ [Cl]-

.

ELECTROSTATIC

ATTRACTION





F-

Fluoride F- Bohr Diagram

p=9

n=10

-1





P=8

N=8

2-

+ 2e-

Oxygen

(Atom)

Oxide

(ion)

P=8

N=8





Ionic Bonding – Bohr Diagrams

The final compound is ALWAYS NEUTRAL

The total charges of the cations and anions must balance

out.

p=17

n=18

Cl

p=17

n=18

Cl-formula

-1

p=11 n=12

Na

p=11 n=12

Na+

+1

Chlorine

atom

Chloride ion(Bohr diagram)

Sodium atomSodium ionNa





Li

Br2

P=

35

n=

45

p=

35

n=

45

Br -

p=

35

n=

45

2Li + Br2

2LiBr

Br -

p=

35

n=

45

--

+ +

Li+ Li

+

Li

Formation of Lithium Bromide





MUST BE LEARNT BY HEART!ONE TWO THREE

Hydrogen H+

Beryllium Be2+

Aluminium Al3+

Lithium Li+

Magnesium Mg2+

Iron(III) Fe3+

Sodium Na+

Calcium Ca2+

Potassium K+

Barium Ba2+

Silver Ag+

Lead Pb2+

Copper(I) Cu+

Zinc Zn2+

Ammonium NH4+

Iron(II) Fe2+

Oxonium H3O+

Copper(II) Cu2+

VALENCY TABLE 1





Bonding - Metallic Bonding

- Exists between _________________.

- Metal electrons are _____________ - therefore they become______________________ (move from one atom to another).

- This leaves _______________ -which become surrounded by a ‘sea’ of ______________________ electrons.

- A force of _______________________exists between the delocalized ___________________ and the positive ___________- which forms the ___________________ bond.

All the _____________ of

metals can be explained

in terms of this bonding.





Bonding Summary

Covalent Non metals

Shared

electrons

Molecules

Ionic

• Metals + non metals

• +/- Ions - Lattice

• electrostatic attraction

Metallic

• Metals

• “delocalised” electrons

H xH•

Cl-Na+

Properties• Non - conducting

• (Electrons held in

bond.)

• V Low or V High

melting points

• Insoluble (H2O)

Properties• High Melting points

• Soluble (H2O)

• Conduct electricity when

ions free to move(liquid

or solution).

Properties• Good Conductors

• Malleable

• Ductile

• Luster (shiny).

H-H

Eg Hydrogen (H2)



BondingElement Number of Bonds(Valency)

Lithium 1

Magnesium 2

Silicon 4

Phosphorus 3

Chlorine 1

Aluminum 3

Arsenic 3

Helium 0

Nitrogen 3





Valency - No of Bonds

Element

SymbolGroup No Period

Valence

electrons

Valency

(Bonds)

Na 1 3 1 1

N

Cl

6 2

1 2

7 2

B 3 2 3 5

Be 2 2

Al 3 3

Si 4 4

H

Hydrogen is an exception - it often reacts as a metal!





BondingElement 1 &

Valency

Element 2 &

Valency

Element 1 -

bonds

Element 2 -

bonds

Compound Formulae

Na +1 Cl -1 Na — Cl— Na —Cl NaCl

H +1 O -2 H— O — H

O

H

H2O

Na +1 S -2

Ca O

H C

Li O

Si O

C O





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WarneScience




bonding

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