Give the symbol or name of the elements that correspond to these configurations.?

Question

(a) 1s22s22p63s1

(b) 1s22s22p63s23p63d104s24p6

(c) 1s22s22p63s23p64s1

Answer 1

Hi,

(a) 1s2 2s2 2p6 3s1
1s, 2s, and 2p are filled in Ne, so the next electron goes in 3s and that's Na.

(b) 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6
All orbits are filled through 4p, so that's Kr.

(c) 1s2 2s2 2p6 3s2 3p6 4s1
The first element with an electron in 4s is K, potassium.

Hope this helps.
FE