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Ionic Bonding
Ions are electrically charged particles formed when atoms lose or gain electrons
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Metal atoms and non-metal atoms go in opposite directions when they ionise:
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

Metal atoms lose the electron, or electrons, in their highest energy level and become
positively charged ions
Non-metal atoms gain an electron, or electrons, from another atom to become
negatively charged ions

There is a quick way to work out what the charge on an ion should be:
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The number of charges on an ion formed by a metal is equal to the group number of
the metal
The number of charges on an ion formed by a non-metal is equal to the group
number minus eight

Representing Positive Ions
You need to be able to show the electronic structure of some common metal ions, using
diagrams like these:
Lithium, Li

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Sodium, Na

Magnesium, Mg

Lithium is in Group 1
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When this
electron is lost, a lithium ion Li+ is formed
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It has one electron in its highest energy level
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Magnesium is in Group 2
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When these
electrons are lost, a magnesium ion Mg2+ is formed
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Representing Negative Ions
You need to be able to show the electronic structure of some common non-metal ions,
using diagrams like these:

Fluorine, F






Chlorine, Cl

Oxygen, O

Fluorine is in Group 7
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It gains an
electron from another atom in reactions, forming a fluoride ion, F-
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Chlorine is in Group 7
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It gains an
electron from another atom in reactions, forming a chloride ion, Cl-
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It has six electrons in its highest energy level
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When metals react with non-metals, electrons are transferred from the metal atoms to the
non-metal atoms, forming ions
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Consider reactions between metals and non-metals, for example:
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sodium + chlorine → sodium chloride
magnesium + oxygen → magnesium oxide
calcium + chlorine → calcium chloride

In each of these reactions, the metal atoms give electrons to the non-metal atoms
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There is a strong electrostatic force of attraction between these oppositely charged ions,
called an ionic bond
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Ionic Compounds
Group 1 and Group 7 - The elements in Group 1 of the Periodic Table are called the alkali
metals
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Their ions have a
single positive charge
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The elements in Group
7 of the Periodic Table are called the halogens
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Their ions have a single negative charge
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Sodium chloride - Ionic lattice of sodium chloride, showing positively charged sodium ions
bonded to negatively charged chloride ions
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It contains oppositely charged ions held together by strong

electrostatic forces of attraction – the ionic bonds
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Formulae of Ionic Compounds
Ionic compounds are represented by formulae
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For example: ZnCO3 is the formula for zinc carbonate
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Notice that we don't need to
write a 1 next to the Zn or C
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For example: Fe(OH)3 is the formula for iron(III) hydroxide
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The formula is written
like this because the oxygen and hydrogen atom often act together
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For example, the
compound formed from Na+ and SO42- will consist of two Na+ ions to every one SO42- ion
so that the compound is neutral overall
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Here are the formulae of some common positive ions (cations):

Here are the formulae of some common negative ions (anions):



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