Question

use the image on the right to answer the next two questions.

1. identify the similarities and differences between the elements in group 1
2. how do the similarities identified change in a group moving from the top to the bottom of the column?

Explanation:

Question 16

Similarities: All Group 1 elements (H, Li, Na, K, Rb, Cs, Fr) have 1 valence electron (outermost shell electron). They are all metals (except H, which is a non - metal but still in Group 1) and show similar chemical reactivity (tendency to lose that 1 valence electron to form +1 ions).
Differences: The number of electron shells increases as we go down the group (H has 1 shell, Li has 2, Na has 3, etc.). Atomic size (radius) increases down the group. Melting and boiling points generally decrease down the group. Also, hydrogen is a gas at room temperature while the rest (except maybe Fr which is radioactive) are solids, and hydrogen has different chemical behavior in many cases compared to the alkali metals (Li, Na, K, etc.).

The main similarity of having 1 valence electron remains. However, the strength of the hold on that valence electron by the nucleus changes. As we move from top to bottom in Group 1, the number of electron shells increases, so the distance between the nucleus and the valence electron increases. This means the effective nuclear charge (the net positive charge experienced by the valence electron) decreases. So, the ability to lose the valence electron (reactivity) increases. Also, the atomic size (radius) increases, and the physical properties like melting point, boiling point, and density show trends (melting/boiling points decrease, density generally increases with exceptions like K being less dense than Na). But the core similarity of 1 valence electron is maintained.

Answer:

• Similarities: All have 1 valence electron; show tendency to form +1 ions (except H in some reactions); belong to Group 1.
• Differences: Number of electron shells increases down the group; atomic size increases; physical states (H is gas, others are solid (except Fr)); chemical reactivity intensity increases down the group (alkali metals become more reactive down the group, H is less reactive in metal - like reactions).

Question 17