The electron affinity of the elements in group 1 to 7

The total number of electrons present in the first twenty elements of the periodic table is 

An element in period-3 whose electron affinity is zero.

The amount of energy released when one or more electrons is added to the neutral atom is 

Which of the element whose atomic number is given below cannot accommodate in the present set up of the long form of the periodic table?

Element 'A' has electronic configuration 2, 7; 'B' has electronic configuration 2, 8, 5 and 'C' has electronic configuration 2, 8, 7. Which two elements will exhibit similar chemical properties?

The non-metallic character of the elements from left to right across the period

The ionization potential across a period

Which of the following sets of atomic number belong to that of alkali metals?

An alkaline earth metal