Question

In the Modern Periodic Table, calcium (atomic number 20) is surrounded by elements with atomic numbers 12, 19, 21 and 38. Which of these have physical and chemical properties resembling calcium?

Answer 1

Hint: Write down the electronic configuration of all the elements given in the question. The elements with the same number of valence electrons to that of calcium will have physical and chemical properties resembling calcium.

Complete-step- by- step answer:
The modern periodic table is a display of chemical elements which are arranged on the basis of atomic number, similar chemical properties and electronic configuration of the elements. Groups and periods are the 2 ways in which elements are categorised in the periodic table. Groups are vertical columns whereas periods are horizontal rows. Elements belonging to the same group will have similar electronic configuration in their outermost shells and hence will have similar chemical and physical properties.

In order to find the elements that have physical and chemical properties resembling calcium, we just have to find those that have electronic configuration similar to that of calcium and hence belong to the same group (Group II).
Calcium, with atomic number 20 has an electronic configuration of – 2,8,8,2. So, let us now write down the electronic configuration of all the other elements and compare it to that of calcium.

Atomic number 12 – 2,8,2
Atomic number 19 – 2,8,8,1
Atomic number 21 – 2,8,8,3
Atomic number 38 – 2,8,18,8,2

We can see that the elements with atomic number 12 and 38 have similar electronic configuration with that of calcium. Also they belong to the same group (Group II).
Hence, elements with atomic numbers 12 and 38 will have physical and chemical properties resembling calcium.

Note: Elements of a period do not have similar electronic configuration. Hence, they do not share much similarity in physical and chemical properties. Only elements in a groups have similar physical and chemical properties.