State reasons for the following statements:
$(i)$ Some elements possess fractional atomic mass.
$(ii)$ Isotopes of an element have similar chemical properties.
$(iii)$ Noble gases are inert.

(N/A) $(i)$ Some elements possess fractional atomic mass because they occur in nature in different isotopic forms. The atomic mass of an element is calculated as the weighted average of the masses of its naturally occurring isotopes.
$(ii)$ Isotopes of an element have similar chemical properties because they possess the same atomic number and the same number of valence electrons,which determine the chemical behavior of an atom.
$(iii)$ Noble gases are inert because the outermost shell of their atoms is completely filled with electrons (stable octet/duplet configuration). Consequently,they do not show affinity towards chemical reactions.