Answer:
c) selenium
Step-by-step explanation:
Selenium is present in group sixteen.
It has six valance electrons.
Its atomic number is 34.
Atomic mass of selenium is 78.96 amu.
Electronic configuration pf selenium:
Se₃₄ = 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁴
we can see there are six valance electrons are present in selenium (4s² 4p⁴).
Valance electrons are those electrons which are present in outer most electronic shell.
Other options are incorrect because,
There are 4 valance electrons in carbon.
2 valance electrons of barium.
one valance electron of lithium.