how many valence electrons does a Nickel have?
The correct answer and explanation is:
Correct Answer: Nickel has 2 valence electrons.
Explanation:
Nickel is a chemical element with the atomic number 28 and the symbol Ni. To determine how many valence electrons it has, first consider its electron configuration. The full electron configuration of a neutral nickel atom is:
1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁸ 4s²
This configuration shows that the 3d and 4s orbitals are the outermost orbitals occupied by electrons. However, when identifying valence electrons for transition metals like nickel, focus is placed on the electrons in the highest principal energy level, which is the 4th level in this case.
In nickel’s configuration, the 4s² electrons are in the outermost shell (n = 4), while the 3d⁸ electrons belong to the third energy level. Therefore, the electrons in the 4s orbital are the true valence electrons of nickel, since they are farthest from the nucleus and participate most readily in chemical bonding.
As a result, nickel has 2 valence electrons, both located in the 4s orbital.
It is important to understand that for main-group elements (like those in Groups 1, 2, and 13-18), the number of valence electrons is often equal to the group number. But for transition metals, the situation is more complex because their d electrons can also be involved in bonding, especially in forming coordination compounds or variable oxidation states. However, when asked to count only the outermost shell electrons, which define chemical reactivity and valence, the correct answer for a neutral nickel atom is 2.
In summary, although the 3d electrons play a role in bonding and in defining the chemical characteristics of nickel, only the 2 electrons in the 4s subshell are considered its valence electrons.