Question

Write the name of the lightest element.

Answer 1

Elements are chemical substances which cannot be further broken into smaller particles by any chemical way. The atomic mass value of lighter elements is low.

Complete step-by-step solution:
We know that a lighter element has a lower value of atomic mass. Hydrogen is the lightest element on the Earth. Hydrogen has the atomic mass value of 1.0079 a.m.u. and the atomic number is 1. It is placed in group 1A in the s-block of the periodic table. As the atomic number of Hydrogen elements is 1, so, it has the electronic configuration ${\rm{1}}{{\rm{s}}^{\rm{1}}}$. The Hydrogen element is colourless and has no specific odour and is formed as ${{\rm{H}}_{\rm{2}}}$, which is a diatomic molecule.
Hydrogen has three isotopes which are Protium, Deuterium and Tritium. Protium present in 99.9 %, deuterium present in 0.01 % and tritium present in very small quantities. Tritium is produced by many nuclear reactions. The electronegativity value of Hydrogen is 2.1 according to Pauling. Hydrogen has a density of ${\rm{0}}{\rm{.0899 \times 1}}{{\rm{0}}^{{\rm{ - 3}}}}{\rm{g}}{\rm{.c}}{{\rm{m}}^{{\rm{ - 3}}}}$ at 20$^{\circ}$C. Hydrogen is also flammable and many reactions may lead to the explosion or can also cause fire. It is soluble solvent water. Hydrogen is less reactive at the normal temperature.

Additional information:
Hydrogen has many uses such as in the fuel refinement, in the synthesis of ammonia, in hydrogenation of the unsaturated vegetable oils, hydrogen is consumed to produce solid fat, hydrogen is used in rocket fuels, in organic chemical products, as rocket propellent.

Note: There are many light elements such as Hydrogen, Helium, Lithium, Sodium and Potassium. Students may get confused in figuring out which is the lightest element. By comparing the values of atomic mass, we can conclude that Hydrogen is the lightest element having atomic mass of 1.0079 a.m.u.