Chemistry - The significance of the 4s subshell
The significance of the 4s subshell
Earlier discussion of the trends across the periodic table showed
significant changes in properties from clearly metallic to clearly
non-metallic, with associated variations in chemical behaviour (e.g. the
change from strongly-reducing to strongly-oxidising) across the
eight-element sets that make up periods 2 and 3. A significant physical
variation is the change from solids at the start of each period to gases at
The first transition series is a 10-element set in which there is much
greater similarity in chemical and physical properties.
All 10 elements are metals and solids at room temperature and have high
melting temperatures. All 10 are reductants.
The name 'transition series' is appropriate because these 10 elements
interrupt - or are a transition in - the changes in properties across
The great similarity in properties across the first row transition series
can be related to the 4s configuration of the outer shell of the atoms of
the 10 elements. While progressive filling of the 3d subshell is a distinct
characteristic of the elements between 21Sc and 30Zn, the similar
properties and chemical behaviour can be linked to the similarity in the
number of electrons - generally two (4s) in the outermost shell. Similarity
in properties across the second and third transition series can be related
to the 5s2 and 6s2 outer-shell electron arrangements respectively.
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