Complete the table given below and answer the following questions (Symbols used are not true.)

a) Which element in the table is the most stable one? Justify your answer.

b) Which element donates electrons in chemical reaction?

c) Write the chemical formula of the compound formed by combining element S with P.

The maximum electrons which can be accommodated in first, second, third shells are 2,8,18 respectively. (The sum of numbers in electronic configuration must be equal to the atomic number). Filling starts from inner orbits. Accordingly, the configuration is given.

a) Element R is most stable.

Atoms with octet configuration are stable. The arrangement of 8 electrons in the outermost orbit of an atom is called octet configuration. These atoms are chemically stable. Atom R contains 8 electrons in its second shell (outermost), hence it is most stable.

b) Element S donates electrons.

Atoms get stability when they acquire octet structure. To acquire octet structure they either gain, lose or share electrons and try to get 8 electrons in the outermost shell.

Now in the case of S, it can easily lose 2 electrons and get stability ( 2^nd shell has octet configuration ) instead of gaining 6 more electrons to get octet structure in 3^rd shell. So, it prefers to donate its 2 electrons and be stable.

c) SP₂ {S is magnesium (atomic no – 12) and P is fluorine (atomic no – 9), so it is MgF_2, magnesium fluoride}.

As explained above, S loses 2 electrons to be stable. P tries to gain 1 electron to get octet structure in 2^nd shell. So, the 2 electrons donated by S are acquired by 2 P atoms to form bond. Thus, both acquire stability and form compound.