Question

Explain the variation of atomic radius in 3d series

Answer 1

For the elements from Sc to Mn the atomic radii decrease. This decrease is because of the gradual increase in nuclear charge with the increase in atomic no. The increased nuclear charge makes the atom shrink in size and hence the size of the atom decreases. However since the electrons added to 3d orbitals screen the 4s electrons, the attraction between the nucleus and the 4s electrons decreases, i. e. due to screening effect caused by 3d electrons to the magnitude of nuclear charge decreases and consequently the atomic radii for the elements from Fe to Cu remain almost uncharged. Towards the end of each series, there is an increase in electron-electron repulsion between the electrons being added to 3d orbitals. This increase in repulsion becomes greater than that of the attraction between the nucleus and the 4s electrons. Because of the greater magnitude of electron-electron repulsion, the electron cloud of Zn expands and hence its size also becomes greater than that of Cu.
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Answer 2

Answer:

Concept:

With an increase in atomic number, the atomic radii of elements in the 3d-series increasingly shrink in radius.

Explanation:

1. Atomic radius typically shrinks over time. However, for the 3d transition elements, the atomic radius decreases as expected from Sc to V, and then virtually stays the same up to Cu.

2. As we progress through the 3d series from Sc to Zn, extra electrons are added to the 3d orbitals, but they only partially shelter the increased nuclear charge, leading to a modest rise in the effective nuclear charge.

3. However, because the additional electrons in the 3d subshell strongly resist the 4s electrons and these two forces operate in the opposite direction, atomic radii remain constant as a result.

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