Ionic and Covalent Bonds: Quiz

Ionic and Covalent Bonds: Quiz

7 questions

1. Question 1EasyWhich pair of elements is most likely to form an ionic compound?

   ACarbon and oxygenBPotassium and chlorineCNitrogen and hydrogenDSulfur and oxygen
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   Answer: Potassium and chlorine

   A metal (K) and a non-metal (Cl) with a large electronegativity difference (3.16 − 0.82 = 2.34). The others are non-metal pairs, which bond covalently.

2. Question 2EasyIn a covalent bond, electrons are…

   Atransferred from one atom to anotherBshared between two atomsCdelocalised throughout a metal latticeDremoved from both atoms
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   Answer: shared between two atoms

   A covalent bond is a shared pair of electrons. Transfer gives ionic bonding; delocalised electrons describe metallic bonding.

3. Question 3MediumUsing EN values C 2.55 and O 3.44, the C–O bond is best described as…

   Anonpolar covalentBpolar covalentCionicDmetallic
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   Answer: polar covalent

   ΔEN = 3.44 − 2.55 = 0.89, between about 0.4 and 1.8, so polar covalent with O δ−.

4. Question 4MediumWhat is the formula of the ionic compound formed by aluminium and oxygen?

   A$\ce{AlO}$B$\ce{Al2O3}$C$\ce{Al3O2}$D$\ce{AlO3}$
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   Answer: $\ce{Al2O3}$

   $\ce{Al^3+}$ and $\ce{O^2-}$: 2 × (+3) = +6 balances 3 × (−2) = −6.

5. Question 5MediumWhich property is typical of an ionic compound?

   ALow melting pointBConducts electricity as a solidCConducts electricity when dissolved in waterDExists as separate molecules
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   Answer: Conducts electricity when dissolved in water

   Dissolved (or molten) ions are free to move and carry charge. In the solid the ions are fixed in the lattice, so it does not conduct.

6. Question 6HardWhen water boils, what is overcome?

   AThe O–H covalent bondsBThe attractions between water moleculesCIonic bonds between H⁺ and O²⁻DThe bonds inside the oxygen nucleus
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   Answer: The attractions between water molecules

   Boiling separates whole molecules; the covalent O–H bonds inside each molecule stay intact.

7. Question 7MediumWhich bond is the most polar? (EN: H 2.20, C 2.55, N 3.04, O 3.44, F 3.98)

   AC–HBN–HCO–HDF–H
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   Answer: F–H

   ΔEN: C–H 0.35, N–H 0.84, O–H 1.24, F–H 1.78. The largest difference gives the most polar bond.