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Which of the following elements does NOT usually form molecules and is found in its atomic form?
Hydrogen
Helium
Nitrogen
Oxygen
Helium
Helium is a noble gas belonging to Group 18 of the periodic table, possessing a completely filled valence shell. Because its outermost electron configuration (1s2) is stable, it does not need to gain, lose, or share electrons, and thus exists naturally as a monatomic element.
Helium is a noble gas belonging to Group 18 of the periodic table, possessing a completely filled valence shell. Because its outermost electron configuration (1s2) is stable, it does not need to gain, lose, or share electrons, and thus exists naturally as a monatomic element.
Think of Helium as a person who is already completely satisfied and has everything they need, so they don't feel the need to join a group or form a partnership to be 'complete'.
Noble Gases (He, Ne, Ar, Kr, Xe, Rn) are 'Lone Wolves' of the Periodic Table.
1s2 тАФ electronic configuration of Helium representing a filled valence shell.
Elements form molecules to achieve a stable electronic configuration, typically an octet (or duplet for hydrogen). Noble gases like Helium have a stable duplet configuration, resulting in high ionization energy and negligible chemical reactivity, which allows them to remain in their stable atomic form without bonding.
Helium is a monatomic gas, meaning it exists as individual atoms.
Hydrogen (H2тАЛ), Nitrogen (N2тАЛ), and Oxygen (O2тАЛ) are all diatomic molecules in their standard state.
Noble gases are chemically inert due to their stable valence electron shells.
Inert nature makes it safe for use in weather balloons and cryogenics.
Used in cryogenics for cooling superconducting magnets.
Used in deep-sea diving gas mixtures to prevent nitrogen narcosis.
Standard state: All noble gases are monatomic at standard temperature and pressure.
Wrong options explanation: Hydrogen, Nitrogen, and Oxygen are reactive non-metals that form stable diatomic covalent molecules (H2тАЛ, N2тАЛ, O2тАЛ) to complete their valence shells.
B is correct тАФ Helium is a noble gas with a complete valence shell, making it inherently stable as a monatomic element.
Always remember the diatomic elements (HONClBrIF: Hydrogen, Oxygen, Nitrogen, Chlorine, Bromine, Iodine, Fluorine) тАФ these always exist as X2тАЛ in nature, unlike the noble gases.
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