Question

which of the following will pair with a group 7 halogen, such as bromine (br), in a 1:1 ratio, based on trends in valence electrons?
potassium (k)
sulfur (s)
aluminum (al)
barium (ba)

Explanation:

Step1: Determine halogen valence electrons

Halogens in group 7 have 7 valence electrons. They want to gain 1 electron to achieve a stable octet.

Step2: Analyze each element's valence - electron behavior

• Potassium (K) is in group 1, has 1 valence electron. It readily loses 1 electron to form a + 1 ion.
• Sulfur (S) is in group 16, has 6 valence electrons. It gains 2 electrons to achieve a stable octet.
• Aluminum (Al) is in group 13, has 3 valence electrons. It loses 3 electrons to achieve a stable octet.
• Barium (Ba) is in group 2, has 2 valence electrons. It loses 2 electrons to achieve a stable octet.

Step3: Find the element for 1:1 ratio

Potassium, which loses 1 electron, can pair with a halogen (which gains 1 electron) in a 1:1 ratio.

Answer:

potassium (K)