Chemistry Topic 3: Ionic Bonding

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  • Created by: Livy
  • Created on: 11-11-13 17:33

What are Ions?

Atoms are neutral, as the protons and electrons are EQUAL. Unfilled outer shell-atoms (e.g. groups1-7) are UNSTABLE

Atoms loose or gain electrons to achieve a full outer shell - STABLE

The number of protons and electrons are now NT EQUALso the atom has a POSITIVE OR NEGATIVE charge

The atom is now an ion.

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How are Ionic Compounds Formed?

They are formed when oppositely charged Ions attract eachother in a GIANT IONIC LATICE.

The attractions between these ions are electrostatic, which means an attraction between positive and negative charges.

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What Becomes Positive and What Becomes Negative?

Metals are POSITIVELY CHARGED (they loose electrons)

Non-metals are NEGATIVELY CHARGED (they gain electrons)

Ionic bonding can only occur between a metal and a non-metal.

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Compound Ion Names

To recap, compound ions can be made of a single ion or a group of ions. 

Names you need to know

Hydroxide  :  OH

Sulphate  :  SO

Nitrate  :  NO

Carbonate  :  CO

Ammonium  :  NH

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Ionic Compounds Continued

There are two types of ions: -ide, which are negatively charged ions of elements

                                         -ate, which are negatively charged compound ions that contain O

 The only exception to this is HYDROXIDE ION, which contains HYDROGEN AND OXYGEN

Ionic compounds are neutral, so the positive and negative charges are equal.

Formula:

Potassium Sulphide:

Magnesium Nitrate:

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Redox and Oxidisation

Redox: reduction and oxidisation

Reduction: when oxygen is removed and electrons are gained by atoms

Oxidisation: When oxygen is added to anything and electrons are lost by atoms

Oxidisation

Is

Loss(of electrons)

Reduction

Is

Gain(of electrons)

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Properties of Ionic Substances

Crystalline : Regular lattice structure

Brittle : Any distortation of crystal will bring ions with the same charge together. They then repel, splitting the crystal

High Melting and Boiling Point : The strong electrostatic attraction between ions requires a lot of energy to break 

Conducts Electricity when Dissolved/Molten : Ions can move around at a liquid, allowing them to carry a charge

Soluble in water : The electrons in the water bond attract to the Oxygen at the end of the bond, so Oxygen is slightly negative. Hydrogen is then short of electrons and positive. Due to this, water is a polar molecule

Polar molecules and the ions in the lattice are attracted

The positive Hyrogen and the negative ions and the negative Oxygen and the positive ions attract

The H O molecules pull the water apart.

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Charge Density

Charge Density = charge/volume

e.g. Li+

CD=2/1=0.5 or a half

The more concentrated the charge is, the more attractive it is (the smaller the CD)

The smaller the ion is, the more attractive it is

The higher the charge, the more attractive the ion is

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