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Topic 4a ­ Bonding
Revision Notes

1) Introduction

Atoms form bonds to get a full outer shell of electrons
Elements in Group 0 (He, Ne, Ar, Kr, Xe, Rn) do not normally undergo chemical
reactions as they have full outer shells and, so, do not need to form bonds to…

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Metallic bonding ­ metals lose their outer shell electrons to produce a lattice of
positive metal ions surrounded by delocalised (free) electrons.

3) Types of Structure

a) Giant ionic lattices e.g. sodium chloride

o Lattice of oppositely charged ions.
o High melting and boiling points (strong forces of attraction between…

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Structure of ice ( is hydrogen, is oxygen)

c) Giant metallic lattices e.g. magnesium

o Lattice of metal ions surrounded by delocalised electrons
o High melting and boiling points usually (strong forces of attraction between
metal ions and free electrons need to be broken)
o Conduct when solid as delocalised…

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4) Electronegativity and bond polarity

Electronegativity is the ability of an atom to attract the electrons in a covalent bond.
When there is a big difference in electronegativity between the atoms at either end of
a covalent bond the electrons will be pulled towards the more electronegative atom
(shared unequally).…

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o Water, ammonia and HF have higher melting and boiling points than expected due to
the strength of the hydrogen bonds that have to be broken
o Ice is less dense than water because, in ice, the molecules are held further apart so
there is more space in the structure

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6) Shapes of Molecules

The following procedure allows the shape of a molecule to be worked out:
Draw a dotcross diagram
Count number of electron pairs round the central atom
Pairs of electrons repel each other and get as far apart as
Lone pairs repel more than bonding pairs…

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Topic 4b ­ Periodicity
Revision Notes

1) Blocks in the Periodic Table

An element can be assigned to the s, p or d block by working out which sublevel its
outermost electron is in:

Na is 1s2 2s2 2p6 3s1 so is in the sblock
O is 1s2 2s2 2p4…

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3) Trends Across Period 3 (NaAr)

Be able to describe and explain trends in the following:

1st ionisation energy Describe ­ general increase
Explain ­ bigger nuclear charge, same shielding
Dip from Mg to Al because Mg is losing 3s electron, Al is losing 3p.
3p is higher in energy,…


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