The lowest oxidation number of an atom in a compound A2B is -2 . The number of electrons in its valence shell is .
Answer
6
Solution
A2B 2A+ + B2-
∵ lowest oxidation number = −(8 − valence electrons) ⇒ B gains 2 electrons to complete its octet
⇒ valence electrons of B = 8 − 2 = 6 (group 16, e.g. O, S)
Answer: 6