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Science 10

Science 10 · Worksheets

Mixed review · The chemistry unit

Ten questions of mixed difficulty, covering Atoms and the table, Compounds and equations. Print it, or work through it on screen — the answer key starts on its own page.

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Mixed review · The chemistry unit

Science 10 · maddyhelps.com

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

  1. Elements are arranged in the modern periodic table in order of increasing

    1. a) atomic number
    2. b) atomic mass
    3. c) density
    4. d) melting point

  2. An atom's nucleus contains

    1. a) protons and neutrons
    2. b) neutrons and electrons
    3. c) only protons
    4. d) protons and electrons

  3. The formula for magnesium chloride is

    1. a) Mg₂Cl₃
    2. b) MgCl₂
    3. c) MgCl
    4. d) Mg₂Cl

  4. The name of N₂O₅ is

    1. a) dinitrogen pentoxide
    2. b) nitrogen(V) oxide
    3. c) nitrogen oxide
    4. d) dinitrogen pentaoxide

  5. An ionic compound forms between

    1. a) two non-metals
    2. b) a metal and a non-metal
    3. c) two metals
    4. d) two noble gases

  6. Compared with metals, non-metals are generally

    1. a) found on the left of the table
    2. b) poor conductors and brittle when solid
    3. c) always gases
    4. d) good conductors and malleable

  7. The ion formed by magnesium is

    1. a) Mg⁺
    2. b) Mg²⁻
    3. c) Mg³⁺
    4. d) Mg²⁺

  8. A reaction is carried out in a sealed container. The total mass afterwards is

    1. a) impossible to predict
    2. b) more, because gas is added
    3. c) the same as before, whether or not a gas was produced
    4. d) less, because gas escapes

  9. Balanced, the combustion of methane CH₄ + ___O₂ → ___CO₂ + ___H₂O needs

    1. a) 1 O₂, 1 CO₂ and 1 H₂O
    2. b) 3 O₂, 1 CO₂ and 2 H₂O
    3. c) 2 O₂, 2 CO₂ and 1 H₂O
    4. d) 2 O₂, 1 CO₂ and 2 H₂O

  10. The atomic number of an element is the number of

    1. a) neutrons in the nucleus
    2. b) electrons in the outer shell
    3. c) protons in the nucleus
    4. d) protons plus neutrons

Answer key · Mixed review · The chemistry unit

Science 10 · maddyhelps.com

  1. a) atomic number — Mendeleev used atomic mass and had to reorder a few pairs to make the families work. Moseley later showed the correct ordering was by proton count, which fixed those exceptions.
  2. a) protons and neutrons — Electrons occupy the space around the nucleus, not inside it. Nearly all of an atom's mass is in the nucleus, and nearly all of its volume is the empty space the electrons move through.
  3. b) MgCl₂ — Mg²⁺ needs two Cl⁻ to balance the charge. The subscripts come from balancing charge, not from anything in the name — ionic names never carry prefixes.
  4. a) dinitrogen pentoxide — Two non-metals means a molecular compound, which takes prefixes on both elements. The a of penta- drops before the vowel, giving pentoxide.
  5. b) a metal and a non-metal — Metals give electrons up and non-metals take them, so the transfer produces oppositely charged ions that attract. Two non-metals share instead, which is a covalent bond.
  6. b) poor conductors and brittle when solid — Metals conduct, bend and shine; non-metals mostly do none of those. The staircase line on the right of the table separates them, and the elements along it are the metalloids.
  7. d) Mg²⁺ — Magnesium is in group 2, so it has two valence electrons to lose. Losing two negatives leaves a 2+ charge — group number predicts the ion charge for the main groups, which is why the table is worth reading rather than memorising.
  8. c) the same as before, whether or not a gas was produced — Sealed is the key word: nothing can leave, so the mass is unchanged. Reactions that appear to lose mass in an open container have simply let a gas out, which is exactly how conservation of mass was missed for so long.
  9. d) 2 O₂, 1 CO₂ and 2 H₂O — One carbon gives one CO₂, and four hydrogens give two H₂O. That needs 2 + 2 = 4 oxygen atoms, which is 2 O₂. Balancing carbon and hydrogen first and leaving oxygen to last is the standard order for combustion.
  10. c) protons in the nucleus — The proton count is what makes an element that element — change it and you have a different element. Changing the neutron count gives an isotope, which is the same element behaving the same way chemically.