Question

determine the number of valance electrons in an atom of each element: Ba, Cs, Ni and S

Answer 1

Valence electrons are electrons present in the outermost orbit of an atom. Atomic no of Ba is 56. Hence there are 56 electrons in the Barium atom and hence its electronic configuration is

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 6s²

As seen there are 2 electrons in the outermost orbit of Ba.

2. Electronic configuration of Cs 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 6s¹. there is one velence electron in Cs.

3. Ni is 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d8, since 4S is incomplete and 3d is also incomplete ( 10 electrons are in 3d)

the valence electrons are 10. Since the neutral Ar has 10 electrons less than that of Ni.

4. Atomic no of S is 16, its electronic configuration is 1s²2s²2p⁶3s²3p⁴. There are 6 electrons in the outermost orbit of S.