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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
possible
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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