The Periodic Table - Group VII properties (3)
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1.
The reactivity of the halogens decreases down the group. Explain why the reactivity of fluorine is greater than that of chlorine, even though both are halogens. Describe one practical application that takes advantage of the high reactivity of fluorine.
Fluorine is the most reactive halogen due to its small atomic size and high electronegativity. Its small size allows it to approach and interact more readily with other atoms, while its high electronegativity means it has a strong tendency to attract electrons. This combination makes it much more likely to gain an electron and form a negative ion compared to chlorine, which is larger and less electronegative.
One practical application that takes advantage of fluorine's high reactivity is in the production of hydrofluoric acid (HF). HF is used as a cleaning agent for glass and also in the etching of silicon in the semiconductor industry. It reacts readily with glass (silicon dioxide) to dissolve it, due to the strong interaction between fluorine and silicon.
2.
Chlorine (Cl2) reacts with sodium (Na) to form sodium chloride (NaCl). Write a balanced chemical equation for this reaction. Explain why this reaction is exothermic.
Balanced equation: 2Na(s) + Cl2(g) → 2NaCl(s)
This reaction is exothermic because of the significant energy released during the formation of the ionic bond between Na+ and Cl- ions. When Na and Cl atoms come together, they form an ionic bond, which releases energy. This energy release is greater than the energy required to initially bring the Na and Cl atoms close together, resulting in an overall exothermic reaction. The electrostatic attraction between the oppositely charged ions is a major contributor to the energy release.
3.
The reactivity series of the alkali metals is: Li > Na > K > Rb > Cs. Predict the relative reactivity of the halogens (F, Cl, Br, I) with sodium (Na). Explain your answer in terms of the factors affecting reactivity.
The halogens' reactivity decreases down the group (F > Cl > Br > I). Therefore, the relative reactivity of the halogens with sodium will be: Na > Cl > Br > I.
This is because reactivity increases up a group in the halogen reactivity series. Sodium is highly reactive, and it will readily lose an electron to form a positive ion (Na+). The halogens will readily gain an electron to form a negative ion (X-). The greater the tendency of the halogen to gain an electron (and therefore the higher its electronegativity), the greater its reactivity with sodium. Fluorine is the most reactive halogen, followed by chlorine, bromine, and then iodine. The weaker the bond between the halogen atoms, the easier it is for the halogen to lose an electron and react with sodium.