The Periodic Table
8 marks · HardThis question is about the arrangement of electrons in atoms and the physical properties of metals and non-metals.
Draw a diagram to show the electronic configuration of an atom of nitrogen (atomic number 7) using shells and dots or crosses to represent electrons.
The atomic number of magnesium is 12, and the atomic number of oxygen is 8. Both elements are found in the same period of the Periodic Table.
State whether magnesium is a metal or a non-metal.
State whether oxygen is a metal or a non-metal.
Describe two physical properties that can be used to distinguish a typical metal such as magnesium from a typical non-metal such as oxygen.
Name one exception to the typical properties of metals or non-metals, as described in this question.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) — · must show two shells drawn, with 2 electrons (dots or crosses) in the first shell and 5 in the second shell
(b(i)) Magnesium is a metal.
(b(ii)) Oxygen is a non-metal.
(c) — · must show property 1: typical metal feature (e.g. high melting/boiling point, shiny, conducts electricity), property 2: typical non-metal feature (e.g. low melting/boiling point, brittle, does not conduct electricity)
(d) Examples: Mercury (liquid metal at room temperature), graphite (conducts electricity as a non-metal), carbon (very high melting point as a non-metal) · must show naming a valid exception (e.g., mercury, graphite, silicon)
Common mistakes: wrong number of electrons in shell diagram; incorrect classification of magnesium or oxygen; listing chemical instead of physical properties
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correct arrangement of shells for nitrogen (2 shells: 2 electrons in the first, 5 in the second).
B2 (a) · 1 mark · Diagrams show correct number of electrons represented with dots and/or crosses.
B3 (b(i)) · 1 mark · Correctly states that magnesium is a metal.
B4 (b(ii)) · 1 mark · Correctly states that oxygen is a non-metal.
B5 (c) · 1 mark · Describes one correct physical property for metal or non-metal.
B6 (c) · 1 mark · Describes a second correct physical property for metal or non-metal.
B7 (d) · 1 mark · Names a valid exception to typical properties of metals or non-metals.
B8 (d) · 1 mark · Describes why this is an exception (e.g. mercury is a liquid, graphite conducts electricity, etc.).
Worked solution
a) Nitrogen (atomic number 7) has 7 electrons. 2 electrons fill the first shell, and the remaining 5 go in the second shell.
b) Magnesium is a metal; oxygen is a non-metal.
c) Metals like magnesium tend to be shiny (have a metallic lustre) and are good conductors of electricity. Non-metals like oxygen are poor conductors and are usually gases with low melting and boiling points.
d) One exception is mercury, which is a liquid metal at room temperature, or graphite, a non-metal that conducts electricity.