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Atoms and the periodic table

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

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Atoms and the periodic table

Science 10 · maddyhelps.com

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

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

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

  2. A metal atom typically forms an ion by

    1. a) losing protons
    2. b) gaining protons
    3. c) gaining electrons, becoming positive
    4. d) losing electrons, becoming positive

  3. Elements in the same column of the periodic table are called a

    1. a) period
    2. b) compound
    3. c) group or family, and behave similarly
    4. d) series

  4. The ion formed by magnesium is

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

  5. Compared with metals, non-metals are generally

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

  6. An atom of carbon-14 has 6 protons. Its number of neutrons is

    1. a) 14
    2. b) 8
    3. c) 20
    4. d) 6

  7. Of these, the element that is a noble gas is

    1. a) chlorine
    2. b) sodium
    3. c) iron
    4. d) neon

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

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

  9. A neutral atom has

    1. a) equal numbers of protons and electrons
    2. b) more protons than electrons
    3. c) no electrons
    4. d) no neutrons

  10. Reactivity increases down group 1 because the outer electron is

    1. a) balanced by a neutron
    2. b) further from the nucleus and more easily lost
    3. c) closer to the nucleus
    4. d) shared with a neighbour

Answer key · Atoms and the periodic table

Science 10 · maddyhelps.com

  1. a) 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.
  2. d) losing electrons, becoming positive — Metals have few valence electrons and let them go easily, leaving more protons than electrons and therefore a positive charge. Non-metals do the opposite, gaining electrons to fill a shell.
  3. c) group or family, and behave similarly — A group shares the same number of valence electrons, which is why they behave alike. A row is a period, and across one the properties change steadily rather than repeating.
  4. c) 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.
  5. c) 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.
  6. b) 8 — The mass number is protons plus neutrons, so 14 − 6 = 8. Carbon-12 and carbon-14 are both carbon because both have 6 protons; they differ only in neutrons, which is what makes them isotopes.
  7. d) neon — Noble gases are the last column, and their outer shell is already full, so they react with almost nothing. That lack of reactivity is the whole reason the column is worth naming.
  8. 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.
  9. a) equal numbers of protons and electrons — Protons are positive and electrons negative and of equal size, so equal numbers cancel. An imbalance produces an ion, and the size of the imbalance is the charge.
  10. b) further from the nucleus and more easily lost — Each period down adds a shell, so the outer electron is further out and more shielded from the nuclear pull. Easier to lose means more reactive — which is why caesium reacts far more violently with water than lithium.