Question

Match the elements in column ‘X’ with the correct group they belong to column ‘Y’.

X	Y
1.Element with atomic number 19	A. Group 18
2.Element with electronic configuration 2	B. Group 16
3.Element with valency of -2	C. Group 1
4.Element ‘P’ which loses 3 electrons to form a cation	D. Group 17
5.Element ‘Q’ in period-3 which has the highest electron affinity	E. Group 13

Answer 1

We know that the periodic table is the chart of elements arranged in increasing order of atomic numbers. The periodic table is divided into eighteen groups and seven periods. The horizontal rows of the periodic table are termed as periods and the vertical columns are termed as columns.

Complete step by step answer:
Let's try to match the columns X and Y one by one.
The element whose atomic number is 19 is potassium. The electronic configuration of potassium is 2,8,8,1. Only one electron is present in the valence shell. So, potassium belongs to group 1 of the periodic table. Therefore, 1 matches with C.
The element whose electronic configuration is 2 is Helium (He). We know that helium is a noble gas. So, helium belongs to group 18 of the periodic table. Therefore, 2 matches with A.
The element with valency of -2 belongs to group 16 of the periodic table. Elements of group 16 such as oxygen, sulphur etc. can gain two electrons to achieve noble gas configuration. For example, the electronic configuration of oxygen is 2,6. So, two electrons needed to achieve octet. So, 3 matches with B.Element 'P' loses 3 electrons to form a cation, that means, P has 13 electrons. So, it can lose its three electrons to achieve stable configuration. So, the element P is Aluminium. The electronic configuration of aluminium is 2,8,3. As it has three valence electrons, it belongs to group 13 of the periodic table. Therefore, 4 matches with E.
Element 'Q' in period-3 has the highest electron affinity. The element Q is chlorine. Chlorine belongs to the group 17 of the periodic table. Therefore, 5 matches with D.

Hence, the correct match is,

X	Y
1.Element with atomic number 19	C. Group 1
2.Element with electronic configuration 2	A. Group 18
3.Element with valency of -2	B. Group 16
4.Element ‘P’ which loses 3 electrons to form a cation	E. Group 13
5.Element ‘Q’ in period-3 which has the highest electron affinity	D. Group 17

Note: According to modern periodic law, the properties (physical or chemical) of elements are periodic functions of atomic numbers. Henry Mosley was the scientist who said that atomic number of elements is better than atomic mass for classification of elements.