A.. Noble gas has closed valence shell. Thus they are stable and do not show any reactivity.

b.. in an atom there are equal number of protons and electrons. So the positive charges of protons are balanced by the equal number of electrons. Thus atom is neutral.

c.. RChemical property is determined by number of electron (in outermost shell) isotopes have equal number of protons (and equal number of electrons). thus they show same chemical properties.

d.. ions loose electron to attain nearest noble gas electronic configuration , and become stable. But atoms does not have filled valence shell. Thus ions are more stable than atoms.

e.. 11Na+ : number of electrons is (11-1)= 10
electronic configuration
K shell : 2electrons (filled),
L shell : 8electrons (filled)
So from electronic configuration we can see Na+ has filled in K and L shell.