how many valence electrons does a Ni^+2 posses?
The correct answer and explanation is:
Correct Answer: Nickel ion (Ni²⁺) has 8 valence electrons.
Explanation:
Nickel is a transition metal with the atomic number 28. The electron configuration of a neutral nickel atom (Ni) is:
Ni: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁸ 4s²
This configuration shows that nickel has two electrons in the 4s orbital and eight electrons in the 3d orbital. In total, a neutral nickel atom has 10 electrons in its outer shells beyond the noble gas core of argon.
When a nickel atom loses two electrons to become a Ni²⁺ ion, it typically loses the two electrons from the 4s orbital first, not from the 3d orbital. This is because the 4s electrons are at a higher energy level and are removed more easily during ionization. So the configuration for Ni²⁺ becomes:
Ni²⁺: [Ar] 3d⁸
Now, the valence electrons are considered as the electrons in the outermost shell that are available for bonding. In transition metals like nickel, the 3d electrons are counted as valence electrons even though they belong to the penultimate energy level.
For Ni²⁺, the 4s orbital is empty after ionization, but the 3d orbital still contains 8 electrons, which are the ones that can participate in bonding or chemical reactions. Therefore, the Ni²⁺ ion has 8 valence electrons.
This concept is important in coordination chemistry and when determining the geometry and bonding of transition metal complexes. Transition metals often form bonds using their d-electrons, and the number of valence electrons directly influences the stability and reactivity of the ion.