Question

With the increase in the atomic number in a period of the periodic table:
A) Electron affinity increases
B) Metallic character decreases
C) Ionization energy decreases
D) Atomic mass decreases

Answer 1

Hint: We know that elements are arranged in a series of rows (periods) in order of increasing atomic number so that the elements with the same properties occur in the vertical column. Elements in the same period have the same number of electronic shells on moving across a period from left to right which thereby decreases the atomic size on moving across the period as the effective nuclear charge also increases.


Complete solution:
On moving left to right across a period the atomic size of the element decreases as the valence electrons are in the same outermost shell also the atomic number increases on moving across the period which in turn also increase the effective nuclear charge and therefore increases the attractive force between the outermost shell and the nucleus of the atom thereby causing a decrease in the atomic size of the element.
And we know that as the atomic size decreases, the electronegativity increases on moving across a period. Electronegativity is the opposite of electro positivity which is also known as the metallic character. Therefore, as the electronegativity increases the metallic character keeps on decreasing.
Also, we know that electron affinity and the ionization energy increase on moving across a period which will cause the elements to readily accept the electrons in their valence shell rather than losing. And on moving down the group we see that as one more shell is added in the atomic radius it becomes easy to remove an electron from the outermost shell as the force of attraction between the nucleus and the outermost shell decreases.
So, the metallic character increases on moving down the group and decreases on moving across a period.

So, clearly we can conclude that the correct answer is Option B.


Note: Metallic character is the tendency of an element to lose electrons easily and non – metallic character is the tendency of the elements to gain electrons easily. The natural element with the highest metallic character is Cesium and the least metallic elements are carbon, phosphorus, Sulphur, bromine and iodine.