Question

1. where are the metalloids located?
2. identify the halogen that has 4 energy levels within the atom?

a. calcium (ca) b. bromine (br)
c. germanium (ge) d. chlorine (cl)
h7.5: ionic radius

1. which has a smaller radius: cl or cl⁻? explain your answer using atomic structure.
2. which has the smaller radius: cl⁻ or k⁺? explain your answer using atomic structure.

Explanation:

Question 4

Halogens are in Group 17. Calcium (Ca) is in Group 2 (alkaline earth metal), Germanium (Ge) is a metalloid, Chlorine (Cl) has 3 energy levels (period 3), Bromine (Br) is in period 4, so it has 4 energy levels and is a halogen.

A chlorine atom (Cl) has 17 protons and 17 electrons. The chloride ion (Cl⁻) has 17 protons but 18 electrons. The extra electron in Cl⁻ increases electron - electron repulsion in the valence shell, causing the electron cloud to expand. So Cl has a smaller radius as its electron cloud is less expanded due to equal protons and electrons (before gaining an electron).

Both Cl⁻ and K⁺ have 18 electrons (isoelectronic). Cl⁻ has 17 protons, K⁺ has 19 protons. The greater positive charge from more protons in K⁺ pulls the electron cloud more tightly towards the nucleus, reducing the radius. So K⁺ has a smaller radius.

Answer:

b. Bromine (Br)

Question H7.5 - 1