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Before comparing simulations of Group 1 metals reacting with water and Group 17 elements reacting with halide ions, a chemistry class uses the periodic table to predict the properties of lithium, sodium, chlorine and bromine.
State what is meant by periodicity.
Explain why metallic character increases from lithium to sodium.
Explain why non-metallic character decreases from chlorine to bromine.
The atomic radii of lithium and sodium are 152 pm and 186 pm, respectively. What is the percentage increase in atomic radius from lithium to sodium, and which element has the greater metallic character?
Answer: A. The percentage increase is [(186 − 152)/152] × 100 = 22.4%. Metallic character increases down group 1, so sodium has the greater metallic character.
B: Calculates the percentage correctly but reverses the group 1 trend.
C: Uses the difference, 34 pm, as the percentage without dividing by the starting radius.
D: Expresses the final radius as a percentage of the starting radius but does not subtract the initial 100%.
Remember: calculate a percentage increase relative to the starting value.
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