Chemistry - Summary of trends in the periodic table
Summary of trends in the periodic table
Behaviour varies significantly across a complete period such as period 3
(Na, Mg, Al, Si, P, S, Cl, Ar). Atomic radius decreases from Na to Cl,
ionisation energy and electronegativity increase from Na to Cl, and the
elements and their compounds show marked variations.
Na, Mg and Al are metals. Si is a covalent network lattice. P4, S8 and Cl2
are discrete molecules. The use of Si in semiconductors hints at some
slight metallic characteristics. So metallic character decreases and
non-metallic character increases across the period.
In terms of redox properties, there is a change from reductants (Na, Mg)
to oxidants (Cl2), i.e. reducing strength decreases and oxidising strength
increases going across the period. The trends going down a group are the
reverse of the trends going across a period.
These trends can also be summarised in the periodic table:
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