Exercises: Groups 1, 2, 17 and 18

State the number of outer-shell electrons in an atom of each of the following:

1. a) lithium
2. b) calcium
3. c) chlorine
4. d) argon

State the physical state at room temperature (solid, liquid or gas) of each of the following:

1. a) chlorine
2. b) bromine
3. c) iodine
4. d) neon

Sodium is stored under oil in a school laboratory.

1. a) Name the group of the Periodic Table to which sodium belongs.
2. b) Explain why sodium is stored under oil.
3. c) Write a balanced equation for the reaction of sodium with water.

Lithium, sodium and potassium are placed in separate troughs of water.

1. a) Arrange the three metals in order of increasing reactivity.
2. b) Explain this trend in terms of atomic radius and the ease of loss of the outer electron.
3. c) Name the gas produced and state how the resulting solution would affect red litmus.

Chlorine gas is bubbled through aqueous potassium bromide solution and the solution turns orange.

1. a) Write a balanced equation for the reaction.
2. b) Explain, in terms of reactivity, why the reaction occurs.
3. c) Predict whether a reaction would occur if iodine solution were added to aqueous potassium chloride, and explain.

Explain each of the following:

1. a) The noble gases are described as unreactive.
2. b) Magnesium is less reactive than calcium.
3. c) Group 1 metals conduct electricity but chlorine does not.

Compare the trend in reactivity going down Group 1 with the trend going down Group 17.

1. a) State the trend in each group.
2. b) Explain both trends in terms of atomic structure, with reference to nuclear charge, shielding and atomic radius.
3. c) Explain why the two trends run in opposite directions even though both involve increasing atomic size.

In 1869 Mendeleev arranged the elements by atomic mass and left gaps in his table. He predicted an element he called "eka-silicon", later identified as germanium.

1. a) Explain how Mendeleev's use of gaps was a strength of his table.
2. b) Give one place where ordering by atomic mass conflicts with ordering by chemical properties (for example, tellurium and iodine), and explain how the modern table resolves this.
3. c) Predict the formula of the chloride of germanium and justify your answer using its group.