EVERYDAY SCIENCE

Detailed explanation-1: -helium (He), chemical element, inert gas of Group 18 (noble gases) of the periodic table. The second lightest element (only hydrogen is lighter), helium is a colourless, odourless, and tasteless gas that becomes liquid at −268.9 °C (−452 °F).

Detailed explanation-2: -It is the second lightest and second most abundant element in the observable universe, after hydrogen. It is present at about 24% of the total elemental mass, which is more than 12 times the mass of all the heavier elements combined.

Detailed explanation-3: -Hydrogen is the lightest element and exhibits the simplest atomic structure.

Detailed explanation-4: -Helium has a molecular weight of 4 and, like hydrogen is lighter than air. While helium is not as light as hydrogen, it is inert and non-flammable (unlike hydrogen, which is highly flammable). For this reason, helium is used to inflate party and meteorological balloons as they will rise in air.

Detailed explanation-5: -Hydrogen, helium, lithium and beryllium are the lightest four elements, with one, two, three and four protons, respectively. Hydrogen has no neutrons, helium has two, lithium has four and beryllium has five, and the masses of the elements increase in that order.