Question

An element \[R\] forms the highest oxide \[{{R}_{2}}{{O}_{5}}\] . The element \[R\] belongs to:
A. group $14$
B. group $15$
C. group $16$
D. group $17$

Answer 1

Hint: The periodic table is defined as a chart in which chemical elements are arranged in groups and periods. The periodic table is used for analyzing a chemical reaction and also to know the physical and chemical properties of an element.

Complete step by step answer:
A period is defined as a horizontal row of chemical elements arranged in the periodic table. There are seven periods in the periodic table. All the elements in a period have the same number of electron shells.
A group is defined as a vertical column of chemical elements arranged in the periodic table. There are eighteen groups in the periodic table. All the elements in a group have the same number of valence electrons.
Valency is defined as the combining capacity of an atom. It is the ability of an atom of an element that can react and combine with the number of atoms of another element.
Now, let us see how to write a chemical formula for a compound. The steps are as follows:
Firstly, we will write the symbols of both the elements.
Below each symbol, write the valency of each element.
Now, we will interchange the valencies.
If the two valencies have a common factor between them, divide them by it and write the valencies in the simplest form.
Now, at last write the formula.
In this question, as we can see the chemical formula of the compound \[{{R}_{2}}{{O}_{5}}\] , two atoms of $R$ have combined with five atoms of oxygen. Therefore, the valency for two atoms of $R$ will be $5\times 2=10\,units$
Hence, for one of $R$ , the valence will be $\dfrac{10}{2}=5\,units$
The valency of element $R$ is $5$ .
To calculate the group number, the formula used is:
$10+$ valency
Now, substituting the value of valency of $R$ in this formula, we get,
$\Rightarrow 10+5=15$
So, the element $R$ belongs to the group $15$ .

So, the correct answer is Option B .

Note: Each element needs to complete its octet and bond with another element to form molecules and become stable.
An element loses or gains electrons, equal to its valency, to combine with another element.
Elements present in the same group have the same valency .