Question

1. which of these halogens is the least reactive on the period table?
2. i
3. br
4. cl
5. f
6. which element has the highest melting point?
7. tantalum
8. rhenium
9. osmium
10. hafnium
11. which element has the greatest density at stp?
12. scandium
13. selenium
14. silicon
15. sodium

Explanation:

• Question 15: Halogens' reactivity decreases down the group. Iodine (I) is lower in the halogen group (Group 17) compared to bromine (Br), chlorine (Cl), and fluorine (F). As atomic size increases down the group, the ability to gain an electron (electronegativity) decreases, making iodine the least reactive among the given halogens.
• Question 16: Rhenium has a melting point of approximately \(3186^{\circ}C\). Tantalum (\(3017^{\circ}C\)), osmium (\(3033^{\circ}C\)), and hafnium (\(2233^{\circ}C\)) have lower melting points than rhenium.
• Question 17: Selenium has a density of \(4.79\ g/cm^{3}\) at STP. Scandium (\(2.99\ g/cm^{3}\)), silicon (\(2.33\ g/cm^{3}\)), and sodium (\(0.97\ g/cm^{3}\)) have lower densities than selenium.

Answer:

1. 1) I
2. 2) rhenium
3. 2) selenium