Cobalt Valence Electrons
Why cobalt has 9
Cobalt has 27 electrons, arranged as 1s2 2s2 2p6 3s2 3p6 3d7 4s2. Counting the 4s electrons plus the 3d electrons gives 9, the usual textbook convention for transition metals. Some courses count only the electrons in the outermost shell, which gives 2 for cobalt; check which convention your class uses.
Cobalt is a transition metal in group 9. Counting its outer s electrons plus the d electrons beneath them gives 9, the same as the group number.
What that means for bonding
Transition metals can lose different numbers of these electrons, which is why cobalt shows several oxidation states (+1, +2, +3, +4, +5). When it forms a cation it loses the 4s electrons first.
Electrons per shell: 2, 8, 15, 2. See the cobalt electron configuration and orbital diagram or the full cobalt data sheet.
Same group, same count
Cobalt valence electrons FAQ
How many valence electrons does cobalt have?
Cobalt has 9 valence electrons. Its electron configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁷ 4s²; the count is 2 outer s + 7 d electrons; 2 in the outermost shell. If your course counts only outermost-shell electrons, the answer is 2.
How do you find the valence electrons of cobalt?
Cobalt is a transition metal in group 9. Counting its outer s electrons plus the d electrons beneath them gives 9, the same as the group number.
How many bonds does cobalt form?
Transition metals can lose different numbers of these electrons, which is why cobalt shows several oxidation states (+1, +2, +3, +4, +5). When it forms a cation it loses the 4s electrons first.