Chemistry · Chemical bonding. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
Atoms bond to reach a more stable, lower-energy arrangement, usually the electronic configuration of a noble gas. How an atom bonds depends on how strongly it holds its own electrons and attracts others. Four properties measure this: atomic radius, ionisation energy, electron affinity and electronegativity.
An ionic bond forms when a metal atom transfers electrons to a non-metal atom and the oppositely charged ions attract each other. A covalent bond forms when two atoms share electrons: one, two or three shared pairs give single, double or triple bonds.
In a coordinate covalent bond both shared electrons come from one atom, the donor. The other atom, the acceptor, has room for the pair.
Students say atoms get bigger across a period because they have more electrons. The extra electrons go into the same shell while the nuclear charge increases, so the atoms get smaller and ionisation energy rises.
Answer: The bond in HCl is polar covalent; the bond in NaCl is mainly ionic.
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