Question

$H{{e}_{2}}$ does not exist since its bond-order is zero.”
Answer whether the above statement is true or false.

Answer 1

The difference between the number of electrons in bonding molecular orbital $({{N}_{B}})$and the electrons in the antibonding molecular orbital $({{N}_{A}})$is known as the Bond order. Bond order is calculated using the following formula-
$\text{Bond order}=\dfrac{{{N}_{B}}-{{N}_{A}}}{2}$

Complete step by step solution:
-Helium was first detected by French astronomer Pierre Janssen in 1868 as a bright yellow line in the spectrum of the chromospheres of the sun during a solar eclipse in India.
-Helium got his name from a Greek word for the sun, ‘helios’.
-Helium is a colourless, odourless, tasteless and is the second most abundant element after hydrogen in the universe. It is one of the noble gases in the periodic table.
-Synthesis of helium can be done by bombarding lithium or boron with high-velocity protons.
-There are nine known isotopes of helium, out of which only helium-3 and helium-4 are stable isotopes.
-$H{{e}_{2}}$has the molecular orbital electronic configuration $\sigma 1{{s}^{2}}{{\sigma }^{*}}1{{s}^{2}}$ .
Bond order of $H{{e}_{2}}=\dfrac{{{N}_{B}}-{{N}_{A}}}{2}=\dfrac{(2-2)}{2}=0$
-But $H{{e}^{+}}$ion exists which have the electronic configuration as $\sigma 1{{s}^{2}}{{\sigma }^{*}}1{{s}^{1}}$
Bond order of $H{{e}^{+}}=\dfrac{{{N}_{B}}-{{N}_{A}}}{2}=\dfrac{(2-1)}{2}$
As the bond order of Helium ion is positive, it exists.

So, the statement in the question is true.

Note: Helium is used for many purposes in different ways. Helium is lighter than air, hence used in airships and sky balloons for easy lifting. Helium offers an advantage over hydrogen because of its lifting power. An atmosphere of helium, oxygen, and nitrogen is used in deep-sea breathing systems by scuba divers and mountain climbers which reduces the risk of nitrogen narcosis and oxygen toxicity at high pressures. Helium is used as a coolant in magnetic resonance imaging, nuclear reactors, and in cryogenics due to its extremely low melting and boiling points. Helium being inert is used as a protective gas in growing silicon and germanium crystals. Helium is also used to pressurize liquid-fuel rockets and in supersonic wind tunnels.