Question

The element with the atomic number 3,11,19,37 and 55 belong to:
A.Alkali metals
B.Alkaline earth metals
C.Halogens
D.Noble gas

Answer 1

Hint: The arrangement of chemical elements in periodic table is done in accordance with their atomic number which represents the actual number of protons that contain the positive charge in the nucleus of the atom. The positive charge of the nucleus is due to the presence of the protons which increases with increase in the atomic number.

Complete step by step answer:
Alkali metals: They are elements found in periodic tables forming the group 1. They are named as alkali metals because on reacting with the water molecules it forms the alkalies (basic in nature).Group 1 include the elements:
 $
 Li\left( 3 \right) \\
  Na\left( {11} \right) \\
  K\left( {19} \right) \\
  Rb\left( {37} \right) \\
  Cs\left( {55} \right) \\
  Fr\left( {87} \right) \\
$
Alkaline earth metals: They are the elements in the periodic table which forms the group 2. They are known as alkaline earth metals because they are in solid state at normal room temperature but oxides of these metals on dissolving with water form the basic solution. Group 2 includes the elements:
$
  Be\left( 4 \right) \\
  Mg\left( {12} \right) \\
  Ca\left( {20} \right) \\
  Sr\left( {38} \right) \\
  Ba\left( {56} \right) \\
  Ra\left( {88} \right) \\
$
Halogens: they are chemical elements forming the group 17 of the periodic table. The word halogen in the Greek mythology means salt producing, so the halogens are named after their property for producing salts on reacting with sodium. The halogens are known for their electronegative property. Group 17 include the elements:
$
  F\left( 9 \right) \\
  Cl\left( {17} \right) \\
  Br\left( {35} \right) \\
  I\left( {53} \right) \\
  At\left( {85} \right) \\
$
Noble gases: they are the elements in the periodic table which forms the group 18 and they are known as noble gas because of their inert nature which is due to the complete electronic configuration in their atomic structure. Group 18 includes the elements:
$
  He\left( 2 \right) \\
  Ne\left( {10} \right) \\
  Ar\left( {18} \right) \\
  Kr\left( {36} \right) \\
  Xe\left( {54} \right) \\
  Rn\left( {86} \right) \\
$

So, the correct answer is Option A.

Note:
Electronic configuration refers to the arrangement of the electrons in the shells of the atoms, which increases with increase in the atomic number of the element. With increase in the atomic number the number of shells increases and the atomic radii of the atom also increases affecting other properties of the atom.