Ionic, covalent, and metallic bonds — why atoms bond the way they do and what that predicts about a compound's properties. Electronegativity difference is the one number that decides which bond type forms. Every question comes with a written explanation of the bond type and why it fits.
A bond only becomes ionic when the electronegativity difference is large enough for one atom to essentially take an electron rather than share it — many compounds between two different nonmetals are covalent instead.
Both involve unequal electron sharing, but a polar covalent bond still shares electrons to some degree — an ionic bond involves an essentially complete transfer, not just an imbalance.
Metallic bonding isn't atom-to-atom like ionic or covalent bonds — it's a lattice of positive metal ions surrounded by electrons that are free to move throughout the whole structure, which is why metals conduct electricity.
Straight from the bank — one per difficulty tier. Reveal the answer to see the explanation you'd get in a real session.
Sodium (a metal) reacts with chlorine (a nonmetal) to form sodium chloride. What type of bond forms between the sodium and chlorine atoms?
A — Ionic bond. A metal (sodium) bonding with a nonmetal (chlorine) transfers an electron rather than sharing it, forming oppositely charged ions that attract each other — an ionic bond. Covalent bond (B) describes electron sharing, which typically happens between two nonmetals, not a metal and a nonmetal.
Two oxygen atoms bond to form O₂. Given that both atoms have identical electronegativity, what type of bond forms?
A — Nonpolar covalent bond. When two atoms with identical electronegativity bond, they share electrons completely equally, since neither atom pulls harder on the shared pair — this is a nonpolar covalent bond. Polar covalent bond (B) would require an electronegativity difference between the two atoms, which isn't the case here since both are oxygen.
A compound forms between two elements with an electronegativity difference of 0.4. Based on typical bonding guidelines, what type of bond is most likely present, and why?
A — Nonpolar or very weakly polar covalent bond, because the electronegativity difference is too small to cause significant electron transfer. A small electronegativity difference like 0.4 falls near the boundary most guidelines use to separate nonpolar from polar covalent bonds — nowhere close to the roughly 1.7 difference typically associated with ionic bonding. Electrons are shared, not transferred, when the difference is this small. Ionic bond (B) confuses "any difference at all" with "a large enough difference to transfer an electron" — real bonds exist on a spectrum, not an all-or-nothing split.
Bonding questions reward knowing the electronegativity-difference spectrum, not just the three bond-type names in isolation.
For every bonding question, think through whether the two elements are metal-nonmetal, nonmetal-nonmetal, or metal-metal before picking a bond type. Untimed practice is where that classification habit sticks.
Move to timed sessions once bond-type classification is instant.
Pair chemical bonding with the periodic table in a mock — electronegativity trends come directly off the table.
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