In: Chemistry
Consider the following species: Na, Mg, Cl^-1,S,Cl,Ar,Na^+
(a) Order the above species in order of increasing atomic/ionic radius.
(b) Order the above species in order of increasing electron affinity
The atomic/ionic radius decreases along a row in a periodic table from left to right . this is because electrons are added same subshell and as a result force of attraction between the nucleus and outermost electrons increases and the atomic/ionic radius increases. All these elements are 3rd period element. The order among the neutral ions are : Na>Mg>S>Cl>Ar.
Now , cations gave lesser ionic radius as in cations the outermost subshell is removed. Onthe other hand anions have longer ionic radius than the neutral element as with more and more number of electrons, nuclear force of attraction on the electrons decreases.
So, the order is Ar<Cl<Cl^-<S<Mg<Na^+,Na
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electrons affinity of an element is defined as the energy released when a electron is added to an element. Electron affinity decreases down the groups and from right to left across the periods on the periodic table because the electrons are placed in a higher energy level far from the nucleus, thus a decrease from its pull.
order among the neutral element : Na<Mg<S<Cl<Ar
Now +ve ions have a greater affinity for -vely charge electron and anions have less affinity as it it already in -ve state. So, the overall order is Na<Na^+<Mg<S<Cl^-<Cl<Ar