Question

The lightest element in the periodic table is _?
a.) Lithium
b.) Fluorine
c.) Hydrogen
d.) helium

Answer 1

Hint: The periodic table is the tabular arrangement of elements found in nature. The elements are arranged according to their chemical properties and size. To find the lightest and heaviest elements, write down the atomic number of the given elements. Use it to determine the number of protons and neutrons as it will give us the average atomic weight.

Complete step by step answer:
We know that the periodic table is a tabular display of chemical elements found in nature. There are 118 elements in the periodic table. They are arranged according to their atomic number, electronic configuration and repetitive chemical properties.
We know that an atom consists of subatomic particles namely proton, neutron and electron. The average atomic weight of an element is given by the number of neutrons and protons in its nuclei.
Let us discuss the elements given to and try to find out the lightest of them.
Lithium has an atomic number of 3, with a chemical symbol of Li. It contains three protons, four neutrons and three electrons. Its atomic mass is 6.941 amu.
Fluorine has an atomic number of 9, with a chemical symbol of F. It contains 9 protons, 10 neutrons and 9 electrons. It is an univalent poisonous gaseous halogen, it is 18.998 amu.
Hydrogen has an atomic number of 1, with the chemical symbol H. It consists of just a single proton and a single electron and no neutrons. It is the lightest gas with an atomic mass of 1.00794 amu.
Helium has an atomic number of 2, with a chemical symbol of He. It consists of two protons, two neutrons and two electrons. Its atomic mass is 4.0026 amu.
We can see from the above discussion that hydrogen has only 1 proton which is responsible for the atomic weight. Thus, hydrogen is the lightest element.
So, the correct answer is “Option C”.

Note: Hydrogen is the lightest element in the periodic table but the periodic table is divided into groups. Among the group 1 elements, lithium is the lightest and among group 17 elements, fluorine is the lightest. Lithium is the lightest alkali metal, with a silvery color and a soft but solid consistency. Fluorine is the most chemically reactive and electronegative of all the elements. It forms compounds even with the noble gases’ krypton, xenon and radon.