Question

The elements with the atomic number 10, 18 belong to the:
(a) Same period
(b) Same group
(c) Different periods
(d) None of these

Answer 1

Hint: The atomic number (also called the proton number) of an element represents the number of atoms present in the nucleus of every atom of that element. It is denoted by the symbol Z.

Complete step by step answer: The periodic table of elements is a display of the chemical elements in a tabular form in which the chemical elements are placed by arranging them by their electronic configuration, atomic number and other chemical properties. There are seven rows on the periodic table which are called periods. They generally have metals on the left side and nonmetals on the right side of the periodic table. There are eighteen columns on the periodic table which are called groups. Group 17 elements are named as halogens and group 18 elements are named as noble gases.
From the periodic table, it can be understood that the atomic number 10 represents the element Neon (Ne) and the atomic number 18 represents the element Argon (Ar). Both of these elements are noble gases or inert gases and belong to the eighteenth group. Thus, the elements with atomic number 10 (Ne), 18 (Ar) belong to the same group which is group 18. So, the correct option is (b).

Additional information:
(1) The elements in the same group tend to display a very clear trend in properties with increase in atomic number.
(2) The groups are vertical columns of the periodic table and are numbered from the left column to the right column from 1 to 18 whereas the periods are the horizontal rows of the periodic table.
(3) The elements in the groups 1 and 2 are termed as s-block elements while the elements in the groups 13 to 18 are called p-block elements. The elements in the groups 3 to 12 are called the d-block elements whereas the lanthanides and actinides fall under f-block.

Note: Elements in the same group generally contain the same number of valence electrons. The elements in group 1 contain one valence electron, elements in group 2 contain two valence electrons, group 13 elements contain 3 valence electrons and so on. So, elements in group 18 contain 8 valence electrons.