Home › KCSE › Chemistry › Chemical Bonding and Molecular Geometry › Why is hydrogen an exception to the octet rule?
Why is hydrogen an exception to the octet rule?
AIt never forms any covalent bonds
BIt always loses its single electron
CIt needs ten electrons to fill up
DIt needs only two electrons to fill up
Answer & Solution
Correct answer: D. It needs only two electrons to fill up
1. Hydrogen's valence shell is the first shell, which holds a maximum of two electrons.
2. So hydrogen is full at two electrons and has no way to reach eight.
3. It therefore forms one covalent bond and stops, which is why it sits outside the octet rule.
4. The transition and inner transition elements are also outside the rule, for different reasons.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 7 "Chemical Bonding and Molecular Geometry", section The Octet Rule_
Related questions
An ionic formula such as Al2O3 does not tell you:For p-block elements forming cations, electrons are removed from which orbitals first?In a chlorine molecule, each chlorine atom ends up surrounded by how many electrons in totA monatomic anion typically forms when a nonmetal atom gains enough electrons to reach:The calcium ion Ca2+ is isoelectronic with which noble gas?When transition metals ionise, the electrons removed first come from the:Breaking the bonds in one mole of hydrogen molecules requires about:Most covalent compounds are poor conductors of electricity because they are: