iGCSE Chemistry (0620) Core:8.2 Group I properties: Exam Style Questions Paper 1- New Syllabus
▶️ Answer/Explanation
Detailed solution:
In Group I, as you go down the group, melting points decrease and densities generally increase. Caesium is near the bottom, so it has a relatively low melting point. For E to have a higher melting point than caesium, it must be above it in the group. Sodium has a certain density; for E to have a lower density than sodium, it must be above sodium. The only Group I element above both sodium and caesium is lithium (Li).
▶️ Answer/Explanation
Detailed solution:
Going down Group I from lithium to sodium to potassium, the atoms get bigger and the single outer electron gets further from the nucleus, making it easier to lose. This means reactivity increases down the group. The melting points of alkali metals are fairly low and they drop as you go down because the metallic bonding gets weaker. Density, however, generally increases down the group as the atomic mass grows faster than the atomic size. So the correct trends are decreasing melting point, increasing density, and increasing reactivity, which matches row A perfectly.
▶️ Answer/Explanation
Detailed solution:
All Group I metals react with water to produce hydrogen gas and a metal hydroxide (statement 1 is correct). Down the group, the melting point actually decreases (not increases), and the density generally increases (not decreases). So statements 2 and 3 are wrong. Reactivity does increase down Group I (statement 4 is correct). That leaves 1 and 4 as the correct pair.