Why are d and f block elements called transition elements?

1 Answer
Nov 23, 2017

They lie between the s-block (metals with low electronegativity) and the p-block (non-metals with high electronegativity) - representing the transition between the two.

They typically are considered to be the titanium family through the copper family.

Explanation:

Transition metals typically have a medium electronegativity, and as such a unique set of behaviours that vary from the s-block metals.

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For example, gold and some of the other "noble metals" are highly resistant to corrosion and tend to remain in their elemental state rather than becoming oxidized, but the s-block metals often favor the oxidized state (like sodium for example).

[This is due to the high electronegativity values (gold is 2.4), whereas s-block metals would have values ranging from just below, to just above 1.0).]

Not all transition metals exhibit this property, but as electronegativity increases during the transition from metal to non-metal, the properties & behaviours begin to vary.

From an electronic point of view, the transition metal have valence electrons that include their ns electrons, while additional electrons are available in the partially-occupied (n-1)d orbitals. From left to right, the d electrons become less and less available for bonding.