Give reasons for the following:
(a) Isotopes of an element are chemically similar. , (b) An atom is electrically neutral
(c ) Nobles gases show least reactivity , (d) Nucleus of an atom is heavy and positively charged
(e ) Ions are more stable than atoms.

Explanation

(a) Isotopes of an element have same atomic number as well as electronic distribution . Since the chemical properties of the element are related to their electronic distribution or configuration the elements with similar configuration have similar properites .Thus the isotopes of an element are chemically similar .
(b) In an atom the number of protons in the nucleus is the equal to the number of electrons in the extra nuclear portion .since each proton and each electron has the same charge but with opposite magnitude atom is therefore electically neutral . (c ) The atoms of the noble gas elements have complete outermost electron shells .With the exception of helium
(He) which has two electrons in its only shell (k shell )the rest of the members of the family have eight electrons in their outermost or valence shell. This means that atoms of these elements have no urge to take part in chemical combination or they are least reactive in nature.
(d) for answer consult section 4.4
(e ) When an atom changs inn to ion (cation or anion) the valence shell of the ion has a complete octert (i.e it has eight electrons in the outermost or valence shell ) .In some ions the valence shell is K shell and it has only two electrons (e.g `Li^(+)` ion or `H^(-)` ion ) The ions are therefore , quite stable in nature.