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KS4 Chemistry

Ionic Bonding

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Full electron shells

Atoms of noble gases, group 8, have completely full outer shells. This makes them very unreactive or stable.

1st shell holdsa maximum of

2 electrons

2nd shell holdsa maximum of

8 electrons

3rd shell holdsa maximum of

8 electrons

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Atoms and electron changes

Every atom would like to have a full outer shell like the noble gases.

Atoms can get full outer electron shells by either gaining or losing electrons

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From atoms to ions

How can reactive metal atoms become stable positive ions?

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Bonding: example 1

• Making sodium chloride – table salt!!!

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It will have to gain an electron!!!

What would a chlorine atom have to do to have a stable electron configuration like a noble gas?

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What would a sodium atom have to do to have a stable electron configuration like a noble gas?

It will have to lose an electron!!!

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Can you think of a way that chlorine could gain an electron and sodium could lose an electron?

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Sodium gives an electron to chlorine!!!

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Once this happens both of the atoms will now be ions and will each have a charge!!

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The oppositely charged ions attract each other and form an ionic bond!!

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Key definitions

An ionic bond is formed when ions that have opposite charges attract

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Formation of an ionic bond

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+ - + - + -+- + - +-

+ + ++ + +

+ + +

- - -- - -

- - -

- + - + -++ - +-

+ ++ + +

+ +

- - -

+-

+

+

-- -- - -

Ionic lattices

In an ionic compound, millions and millions of ions are packed all joined by ionic bonds

+ - + - + -

+- + - +-

+ + ++ + +

+ + +

- - -- - -

- - -

- + - + -

++ - +-

+ ++ + +

+ +

- - -

+-

+

+

-- -- - -

+ - + - + -

+- + - +-

+ + ++ + +

+ + +

- - -- - -

- - -

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Bonding example 2

• Making Magnesium oxide

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What would magnesium need to do to get a stable full outer shell?

Mg

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O

What would oxygen need to do to get a stable full outer shell?

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Mg O

Can you think of a way that Magnesium could lose two electrons and oxygen could gain two electrons?Magnesium gives two electrons to oxygen!

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Once this happens the Magnesium and Oxygen atoms each get charge and become ions of opposite charge

2.8.2 2.6[2.8]2+ [2.8]2-

Mg

2+2-

O

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Magnesium oxide: part 2

Mg O

The positive magnesium ions and the negative oxygen ions are strongly attracted to each other and form an ionic bond.

+2 -2

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+ - + - + -+- + - +-

+ + ++ + +

+ + +

- - -- - -

- - -

- + - + -++ - +-

+ ++ + +

+ +

- - -

+-

+

+

-- -- - -

Ionic lattices

In an ionic compound, millions and millions of ions are packed together in a regular cubic arrangement, joined by ionic bonds..

+ - + - + -

+- + - +-

+ + ++ + +

+ + +

- - -- - -

- - -

- + - + -

++ - +-

+ ++ + +

+ +

- - -

+-

+

+

-- -- - -

+ - + - + -

+- + - +-

+ + ++ + +

+ + +

- - -- - -

- - -

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Formation of an ionic bond

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Multiple-choice quiz

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Compounds

Compounds are made up of two OR MORE different elements chemically combined

Example: water – H20

O

H

H

Others compounds, like DNA, have large, complex structures containing thousands or even millions of bonded atoms.