The following table shows the position of six elements A, B, C, D, E, and F.in the modern periodic table: Out of D and E which one has a bigger atomic radius and why?

Element D has a bigger atomic radius than E. In the third-period element D comes first then the element E. Hence, element D has bigger atomic radius. Atomic radius decreases in moving left to right along a period. This due to an increase in nuclear charge which tends to pull the electrons closer to the nucleus and reduces the size of the atom.

The following table shows the position of six elements A, B, C, D, E, and F.in the modern periodic table: Which element is a non-metal with valency 3?

A non-metal with valency 3 is B. An element is called a non-metal if it has 5, 6, 7, or 6 electrons in its valence shell. Therefore, a non-metal needs 3, 2, 0r 1 electrons to complete its octet. Thus, the valency of a non-metallic element = 8 - the number of electrons in the outermost shell.

The following table shows the position of six elements A, B, C, D, E, and F.in the modern periodic table: Which element is a metal with valency 2?

Element D has valency of 2 since it is in group 2. Group number indicates the valency of an element. Groups in the Periodic Table signify an identical outer electronic configuration. On the other hand, the number of shells increases as we go down the group. Group 2 elements are known as alkaline earth metals.

State two demerits of Mendeleev's classification of elements.

1. No proper position could be given to the element hydrogen. In the periodic table, the location of hydrogen is uncertain. It was put with alkali metals within 1A class, but certain hydrogen properties are close to those of halogens. So, it can also be put for halogens in the band. 2. As isotopes are atoms of the same element having different atomic masses, they should have been given different positions while arranging them in the order of atomic mass. But this was not done.