What is the ground-state electron configuration of chlorine and the number of valence electrons in it?

Explanation:

Chlorine is an element in group 7 on the periodic table.

  It is the second element in this group of halogens

 The element has a total of 17 electrons:

Ground state configuration  = 1s² 2s² 2p⁶ 3s² 3p⁵

Valence electrons are the outermost shell electrons;

  From the configuration: 3s² 3p⁵ is the valence shell

           Number of electrons  = 2 + 5  = 7

percent abundance for cu-63 can be shown as:

63 x + 65 (1-x) = 62.9296

65 - 62.9296 = 2 x

x = 1.035

thus, percent abundance for cu-63 is 1.035

percent abundance for cu-65 can be shown as:

63 x + 65 (1-x) = 64.9278

65 - 64.9278 = 2 x

x = 0.0361

thus, percent abundance for cu-63 is 0.0361

the mass spectrum of cu-63 showing the intense peak as, this isotope is found in nature more abundantly around 92.38 % in comparison to cu-65 which is found 62.58 % naturally