Question

Give scientific reasons:

(a) An atom is electrically neutral though it contains charged particles.

(b) Two electrons in Helium are placed in only one shell while three electrons in Lithium occupy two shells.

Answer 1

(a) The atom, containing charged particles, is electrically neutral because in an atom, magnitude of positive charge i.e., number of protons is equal to the magnitude of negative charge i.e., number of electrons.

(b) In an atom, the 1^st shell i.e., K shell can have a maximum of two electrons only.

Helium (He) atom has two electrons, both of which are present in the K shell.

Lithium (Li) atom has three electrons in it. As the K shell can have only two electrons, the third electron is transferred to the next shell i.e., the L shell.