Fig. 6.1 shows the electron arrangements of atoms of three Group I metals, labelled X, Y and Z. The letters are not the real chemical symbols. (a) State the...
Question 1 Report
Fig. 6.1 shows the electron arrangements of atoms of three Group I metals, labelled X, Y and Z. The letters are not the real chemical symbols.
(a) State the number of outer-shell electrons in each of these atoms and hence the group they belong to. [2]
(b) Deduce the proton number of atom Y. [1]
(c) Place X, Y and Z in order of increasing reactivity, starting with the least reactive. [1]
(d) Explain, in terms of electron loss and distance from the nucleus, why the reactivity changes in this order. [3]
(e) Each of these metals reacts with cold water. Describe two observations you would expect when metal Z is added to water, and name the gas produced. [3]
(f) Write a balanced symbol equation for the reaction of a Group I metal M with water, giving the metal hydroxide and the gas. [2]
(g) State the pH range of the solution formed when these metals react with water. [1]
Answer Details
What this tests: Group I electron arrangements and the trend in reactivity down the group.
The diagrams show X as 2,1; Y as 2,8,1; and Z as 2,8,8,1.
(a) Each atom has 1 electron in its outer shell [1], so all three belong to Group I [1].
(b) Y is arranged 2,8,1, so its proton number = \(2+8+1 = 11\) [1].
(c) In order of increasing reactivity (least reactive first): X, Y, Z [1].
(d) These metals react by losing the single outer electron [1]. Going from X to Z the outer electron is in a shell further from the nucleus and more shielded by inner shells [1], so it is held less strongly and lost more easily, which increases reactivity [1].
(e) Z is the most reactive, so with cold water expect it to float and move about on the surface, melting into a ball from the heat released [1], and to fizz/effervesce, possibly catching fire with a coloured flame [1]; the gas produced is hydrogen [1].
(f) \(2M + 2H_2O \rightarrow 2MOH + H_2\) - correct products [1], correctly balanced [1].
(g) The solution formed is alkaline, with a pH greater than 7 (about 11 to 14) [1], because a soluble metal hydroxide is produced.
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