Give a reason to explain why
$(a)$ isotopes of an element show identical chemical properties?
$(b)$ the atomic masses of elements are in fractions?
$(c)$ atoms combine with other atoms?

(N/A) Isotopes of an element have identical electronic configurations,meaning they possess the same number of valence electrons. Since chemical properties are determined by valence electrons,all isotopes of an element exhibit identical chemical properties.
$(b)$ The atomic mass of an element is the weighted average of the masses of its naturally occurring isotopes. Because these isotopes have different masses and exist in specific natural abundances,the resulting average atomic mass is often a fraction.
$(c)$ Atoms combine with other atoms to attain the stable electronic configuration of the nearest noble gas (octet or duplet rule),thereby reducing their potential energy and becoming more stable.