Question

1. An atom of an element has three electrons in its 3rd orbit, which is the outermost shell. Write
(i) the electronic configuration
(ii) atomic number
(iii) number of protons, electrons, neutrons
(iv) valency

Answer 1

here is your ans.. hope it will helpful

Answer 2

The atom has three electrons in the third shell which is the M shell. This means the K shell and L shell is filled. The K shell contains maximum 2 electrons and L shell contains maximum 8 electrons.

• (i) The electronic configuration of the atom is 1s²2s²2p⁶3s²3p¹.
• (ii) The atomic number of an atom is the number of electrons. The atom has filled K shell, L shell and has 3 electrons in M shell. Therefore the total number of electrons in the atom is 2 + 8 + 3 = 13 electrons. The atomic number of the atom is 13.
• (iii) The number of electrons is equal to the number of protons. The number of electrons is also the atomic number of the element. Therefore, the no. of electrons is 13 and the no. of protons is 13. The no. of neutrons is dependent on the atomic mass of the element.
• (iv) The valency of the element is the no. of electrons it can donate or accept to attain stability. Since it has 3 electrons in the outermost shell, it can donate 3 electrons to attain stability. Hence the valency is 3+.