a) Identify the group:
The elements listed in the table are Fluorine (F), Chlorine (Cl), Bromine (Br), and 1. These elements belong to Group 17 of the modern periodic table, also known as the Halogens.
b) Change in reactivity when moving from top to bottom in Group 17:
As we move from top to bottom in Group 17, the reactivity of the elements decreases. This trend occurs due to the following reasons:
- Atomic size: The atomic size increases as we move down the group. Consequently, the distance between the nucleus and the valence electrons becomes larger.
- Shielding effect: The number of inner electron shells increases downward, causing a greater shielding effect. This reduces the effective nuclear charge felt by the outermost electrons.
- Electron affinity: Although halogens have a high electron affinity, it decreases slightly down the group because it's harder for larger atoms to attract additional electrons to their valence shells.
Due to these factors, the elements at the top of the group (like Fluorine) are more reactive than those at the bottom (like Iodine).
c) Balanced chemical equation:
The element of Group 17 belonging to the [tex]$3^{\text{rd}}$[/tex] period is Chlorine (Cl). An element from Group II-A (Group 2) is Calcium (Ca).
The balanced chemical reaction between Calcium (Ca) and Chlorine (Cl) is:
[tex]\[ \text{Ca} + \text{Cl}_2 \rightarrow \text{CaCl}_2 \][/tex]
Explanation:
- Calcium (Ca) is a group 2 element and forms divalent cations, i.e., [tex]\( \text{Ca}^{2+} \)[/tex].
- Chlorine (Cl) is a halogen and forms monovalent anions, i.e., [tex]\( \text{Cl}^{-} \)[/tex].
- One Calcium atom combines with two Chlorine atoms to form Calcium Chloride (CaCl₂).
Thus, when Calcium reacts with Chlorine, the balanced chemical equation is:
[tex]\[ \text{Ca} + \text{Cl}_2 \rightarrow \text{CaCl}_2 \][/tex]
