Question

The position of $3$ elements A, B and C in the periodic table is shown above: Give reasons, explain the following:
(a) Element A is a non-metal.
(b) Atoms of element C have a larger size than A.
(c) Element B has a valency of $1$

$Group \to$ $Period \downarrow$	$1$	$16$	$17$
$1$	$B$
$2$			$A$
$3$		$C$

Answer 1

The above representation is just like periodic table, you have to think about the elements A, B and C using the hint given below. Group $1$ element are all alkali metals having valency of $1$ thus now see in which period B belongs according to the above diagram, it is from period $1$ thus you have to give name of that element that is present in group $1$ and period $1$ .

Complete step-by-step answer: We know that the above representation is given to us for predicting the elements that are labelled. So, if you have little knowledge about the periodic table you can easily solve the questions. Let’s take option (a) where we have to find out the name of element A, the hind is given as it is a non-metal now our task is to see the labeling and find out in which period and in which group it belongs.
For an element it is given that it exists in the group $17$ and period $2$ , let’s remember which element is present in the periodic table. The element which is present there is fluorine, now lets’ recheck the hint we have given in the question that the element is a non-metal. So, yes fluorine is a non-metal.
Element A is fluorine.
Next we have element B as it is given in last option that B is having a valency of $1$ now if you see the diagram represented for it, it is having position as group $1$ and period $1$ so now according to the periodic table and the element which is having these positions is hydrogen (H).
Element B is hydrogen.
Al last we left with element C so if you see the second comment about element C you will get an idea about its size, size of C is larger than size of A element so let’s see its representation in the diagram. You will see that this element is having a period no. $3$ and group no. $16$ . It means this element is from the oxygen family and it is sulphur.
Element C is sulphur.

Note: Whenever you are solving these types of problem in which you have to find out the original element in place of A, B and C. Try to find out from which group it belong, the group name is according to the first element as they have example- Oxygen family. After that try to remember the elements of family and use hints for solving them.