Chemical Bonding

Sample questions

Showing 10 of 70 questions from this chapter. The full bank is in the chapter test below.

1. 1

   A chemical bond is formed between two atoms when:

   • A.✓ the force of attraction between them overcomes the force of repulsion (correct answer)
   • B.the force of repulsion between them becomes equal to the force of attraction
   • C.the force of repulsion between them becomes greater than the force of attraction
   • D.both atoms lose all of their valence shell electrons

   Why: A bond exists only when the net interaction between the two atoms is attractive, so attraction must dominate repulsion. If repulsion is equal to or greater than attraction, the atoms separate instead of bonding.
2. 2

   An ionic compound A+$\ce{B-}$ is most likely to be formed when:

   • A.the ionization energy of A is high and the electron affinity of B is low
   • B.✓ the ionization energy of A is low and the electron affinity of B is high (correct answer)
   • C.the ionization energy of A and the electron affinity of B are both high
   • D.the ionization energy of A and the electron affinity of B are both low

   Why: Ionic bonding requires that A lose electrons easily, which needs a low ionization energy, and that B attract them strongly, which needs a high electron affinity.
3. 3

   According to the Lewis concept, an ionic bond is formed by:

   • A.the mutual sharing of one or more pairs of electrons between two atoms
   • B.the donation of a lone pair of electrons by one atom to another atom
   • C.✓ the complete transfer of electrons from one atom to another atom (correct answer)
   • D.the sideways overlap of two parallel half-filled p orbitals

   Why: An ionic bond involves complete transfer of electrons, so the atoms become oppositely charged ions that attract each other. Mutual sharing produces a covalent bond and lone-pair donation produces a dative bond.
4. 4

   A sodium atom loses its outermost electron to give the $\ce{Na+}$ ion. The electronic configuration of $\ce{Na+}$ (2,8) is the same as that of:

   • A.He
   • B.Ar
   • C.Kr
   • D.✓ Ne (correct answer)

   Why: Sodium (2,8,1) loses one electron to give $\ce{Na+}$ with the configuration 2,8, which is exactly the configuration of neon, the noble gas nearest to sodium in the periodic table.
5. 5

   A covalent bond is formed between two atoms by:

   • A.the complete transfer of one electron from one atom to the other
   • B.✓ the mutual sharing of one or more electron pairs between the two atoms (correct answer)
   • C.the transfer of a complete lone pair from one atom to the other atom
   • D.the electrostatic attraction between two oppositely charged ions

   Why: In a covalent bond the two atoms share one or more electron pairs, and each atom thereby completes its valence shell. Transfer of electrons gives ions, not a covalent bond.
6. 6

   Which set contains only non-polar covalent molecules?

   • A.HCl, HBr, $\ce{H2O}$
   • B.HF, $\ce{Cl2}$, $\ce{Br2}$
   • C.✓ $\ce{H2}$, $\ce{F2}$, $\ce{I2}$ (correct answer)
   • D.$\ce{H2O}$, $\ce{NH3}$, HCl

   Why: $\ce{H2}$, $\ce{F2}$ and $\ce{I2}$ are each formed between two identical atoms, so the electronegativity difference is zero and the bond is purely non-polar. The other sets contain bonds between different elements, which are polar.
7. 7

   A dative (coordinate) covalent bond is formed when:

   • A.each of the bonded atoms contributes one electron to the shared pair
   • B.the shared pair of electrons is transferred completely to one of the atoms
   • C.two half-filled orbitals of similar energy overlap with each other
   • D.✓ the shared pair of electrons is donated by only one of the bonded atoms (correct answer)

   Why: In a dative bond the shared pair comes from one atom only, normally a lone pair, and the other atom accepts it. When both atoms contribute one electron each the bond is an ordinary covalent bond.
8. 8

   When a water molecule accepts a proton ($\ce{H+}$) to form the $\ce{H3O+}$ ion, the new bond formed is:

   • A.✓ a dative bond in which oxygen donates one of its lone pairs to the proton (correct answer)
   • B.an ionic bond formed between the proton and the oxygen atom of water
   • C.a pi bond formed by the sideways overlap of two p orbitals
   • D.a hydrogen bond formed between two neighbouring water molecules

   Why: Oxygen carries two lone pairs and the proton is electron deficient, so oxygen donates one lone pair to the proton and the third $\ce{O-H}$ link is a dative bond.
9. 9

   Carbon monoxide contains a dative bond because:

   • A.oxygen transfers two electrons completely to the carbon atom
   • B.carbon donates one of its lone pairs of electrons to oxygen
   • C.✓ oxygen donates a lone pair to carbon, whose octet is still incomplete (correct answer)
   • D.carbon and oxygen each contribute one electron to the shared pair

   Why: The two atoms share two pairs of electrons in a normal double bond, but carbon's valency is still not satisfied, so oxygen donates a lone pair to carbon and that third link is a dative bond.
10. 10

    In the ozone molecule, the central oxygen atom is:

    • A.joined to both the other oxygen atoms by two single covalent bonds
    • B.surrounded by three lone pairs of electrons and no bond pair
    • C.carrying a partial negative charge while the terminal atoms are positive
    • D.✓ joined to one oxygen by a double bond and to the other by a dative bond (correct answer)

    Why: One oxygen atom (the free radical) accepts a lone pair donated by the central oxygen atom, so the central atom has a double bond on one side and a coordinate covalent bond on the other, and it carries the positive charge.