How many valence electrons does a nickel atom Ni) have?
The Correct Answer and Explanation is:
Correct Answer: 2 valence electrons
Nickel (Ni), with the atomic number 28, belongs to the transition metals in Group 10 of the periodic table. The electron configuration of a neutral nickel atom is:
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁸
To determine the number of valence electrons, attention must be given to the electrons in the outermost shell. In the case of nickel, the outermost principal energy level is n = 4, which contains 4s². The 3d⁸ electrons are in the inner shell (n = 3), so they are not counted as valence electrons under a strict definition that considers only the highest principal energy level.
Thus, nickel has 2 valence electrons, both found in the 4s orbital.
However, in chemical bonding and coordination chemistry, the 3d electrons can participate in reactions, particularly because transition metals often use both their s and d electrons. As a result, in some contexts, the d-electrons may be considered as part of the “valence shell” when discussing reactivity or bonding in coordination compounds. Despite this, the standard definition based on the outermost shell limits valence electrons to the 4s² electrons only.
This limited number of valence electrons explains nickel’s typical oxidation states, which are +2 and sometimes +3. The +2 oxidation state results from the loss of the two 4s electrons. Because of its electron configuration, nickel is chemically versatile and forms various complex compounds, especially in coordination chemistry and catalysis.
In summary, the nickel atom possesses 2 valence electrons, located in the 4s orbital, which primarily influence its chemical reactivity and bonding behavior in most compounds.
