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Chemistry 20

Chemistry 20 · Worksheets

Mixed review · Bonding and naming

Ten questions of mixed difficulty, covering Bonding, Names and formulas. Print it, or work through it on screen — the answer key starts on its own page.

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Mixed review · Bonding and naming

Chemistry 20 · maddyhelps.com

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Circle the best answer for each question. Show your work in the space provided.

  1. The formula for calcium chloride is

    1. a) CaCl₂
    2. b) Ca₂Cl
    3. c) Ca₂Cl₃
    4. d) CaCl

  2. A covalent bond forms when two atoms

    1. a) transfer a pair of electrons
    2. b) exchange protons
    3. c) are both metals
    4. d) share a pair of electrons

  3. The name of N₂O₄ is

    1. a) nitrogen tetroxide
    2. b) dinitrogen tetraoxide
    3. c) nitrogen(IV) oxide
    4. d) dinitrogen tetroxide

  4. The name of MgO is

    1. a) magnesium oxygen
    2. b) magnesium(II) oxide
    3. c) magnesium oxide
    4. d) monomagnesium monoxide

  5. Carbon tetrachloride, CCl₄, has polar C–Cl bonds, yet the molecule is non-polar because

    1. a) the molecule is linear
    2. b) chlorine and carbon have the same electronegativity
    3. c) the lone pairs on chlorine cancel the dipoles
    4. d) its tetrahedral shape makes the four bond dipoles cancel

  6. The Lewis structure of CO₂ contains

    1. a) two carbon–oxygen triple bonds
    2. b) two carbon–oxygen double bonds, in a linear arrangement
    3. c) one double and one single bond
    4. d) two carbon–oxygen single bonds, in a bent arrangement

  7. Of these two molecules, the polar one is

    1. a) CO₂, because its C=O bonds are polar
    2. b) neither, because both are symmetrical
    3. c) both, because both contain polar bonds
    4. d) H₂O, because its bent shape leaves the bond dipoles uncancelled

  8. Of these substances, the one expected to have the lowest melting point is

    1. a) CaF₂
    2. b) NaCl
    3. c) MgO
    4. d) CH₄

  9. The shape of an ammonia molecule, NH₃, is

    1. a) trigonal planar
    2. b) bent
    3. c) tetrahedral
    4. d) trigonal pyramidal

  10. The IUPAC name of CH₃CH₂CH₂CH₃ is

    1. a) butane
    2. b) methane
    3. c) butene
    4. d) propane

Answer key · Mixed review · Bonding and naming

Chemistry 20 · maddyhelps.com

  1. a) CaCl₂ — Calcium is Ca²⁺ and chloride is Cl⁻, so two chlorides are needed to balance one calcium. The subscript comes from balancing charge, not from the name.
  2. d) share a pair of electrons — Two non-metals both want to gain electrons, so neither can take them outright. Sharing lets both count the pair towards a full outer shell.
  3. d) dinitrogen tetroxide — Both elements take prefixes in a molecular compound: di- for two nitrogens and tetr- for four oxygens. The a is dropped before the vowel, giving tetroxide rather than tetraoxide.
  4. c) magnesium oxide — Metal first with its element name, then the non-metal with an -ide ending. No prefixes, because ionic charges fix the ratio. No Roman numeral, because magnesium only ever forms Mg²⁺.
  5. d) its tetrahedral shape makes the four bond dipoles cancel — Four identical bonds pointing to the corners of a tetrahedron pull equally in every direction, so the vector sum is zero. Symmetry is what decides this, which is why the shape has to be worked out before polarity can be.
  6. b) two carbon–oxygen double bonds, in a linear arrangement — Carbon has four valence electrons and each oxygen needs two more, so carbon forms a double bond to each oxygen. With two bonding groups and no lone pairs on carbon, VSEPR puts them as far apart as possible: 180° apart, linear.
  7. d) H₂O, because its bent shape leaves the bond dipoles uncancelled — Both contain polar bonds, but polarity of a molecule depends on shape as well. Carbon dioxide is linear, so its two dipoles point in exactly opposite directions and cancel. Water is bent, so they add to give a net dipole.
  8. d) CH₄ — The other three are ionic and have to break a whole lattice to melt. Methane is molecular, so melting only has to overcome the weak forces between separate molecules — its covalent C–H bonds stay intact.
  9. d) trigonal pyramidal — Nitrogen has four electron groups — three bonds and one lone pair — so the groups point to the corners of a tetrahedron. Shape is named for the atoms only, and with one corner occupied by a lone pair the three hydrogens form a pyramid.
  10. a) butane — Count the carbons: four, which is the prefix but-. Every bond between carbons is single, so the ending is -ane. An -ene ending would mean a double bond somewhere in the chain.