Question

The valency of elements in the periodic table in respect of hydrogen:
A) Increases regularly from 1 to 8
B) Decreases regularly from 1 to 8
C) First increases from group I to group IV and the decreases.
D) First decreases from group I to group IV and the increases.

Answer 1

The answer to this question lies in the trends of the periodic table in which the atoms are arranged according to the increasing atomic number and the valency where valency is the number of valence electrons present in the outermost shell.

Complete answer:
In the lower classes, we have studied the various periodic tables proposed by several scientists and about the present periodic table which is called the modern periodic table.
We have also seen the trends in the periodic table about their valency, electron affinity and many other parameters.
Now let us see how valency of the atoms varies with respect to the first element in the periodic table that is hydrogen.
- Valency is nothing but the combining capacity of atoms or the molecules and it measures the total number of electrons that are present in the outermost orbit of the shell.
- Thus, according to this definition, we can say that valency is concerned mainly with the number of valence electrons or can also be calculated as 8 minus the number of electrons present in the outermost shell.
Based on this data, by looking into the periodic table, we can say that the number of valence electrons increases up to group IV and then because of the addition of electrons in the same shell, the valency decreases.

Therefore, the correct answer is option C).

Note:
Note that the maximum number of valence electrons that an outermost shell can accommodate is eight according to the octet rule which states that the atoms tend to form the compounds in a way that gives them eight valence electrons and therefore, is the electronic configuration of noble gas..