Question

name: ____ pd: ____ chemistry u3l14 q2 ct module day 5
note: annotate all questions & diagrams!
cross out both of the answer choices that makes your answer incorrect.

1. which of the following ions has the same number of electrons as br⁻?

(a) k⁺
(b) sr²⁺
(c) i⁻
(d) cl⁻
** 2. if na reacts with chlorine to form nacl, which of the following elements reacts with na to form an ionic compound in a one - to - one ratio, and why?
(a) k, because it is in the same group as na.
(b) mg, because its mass is similar to that of na.
(c) ar, because its mass is similar to that of cl.
(d) br, because it has the same number of valence electrons as cl.
** 3.
the complete photoelectron spectrum for an element is shown above. which of the following observations would provide evidence that the spectrum is consistent with the atomic model of the element?
(a) a natural atom of the element contains exactly two electrons.
(b) the element does not react with other elements to form compounds.
(c) in its compounds, the element tends to form ions with a charge of +1.
(d) in its compounds, the element tends to form ions with a charge of +3.
annotate the location of \mussels\ & dominant annonation! y

Explanation:

Step1: Find electron count of Br⁻

Br has 35 electrons; Br⁻ gains 1 → 36 electrons.

Step2: Check each ion's electron count

(A) K⁺: K (19 e⁻) loses 1 → 18 e⁻
(B) Sr²⁺: Sr (38 e⁻) loses 2 → 36 e⁻
(C) F⁻: F (9 e⁻) gains 1 → 10 e⁻
(D) Cl⁻: Cl (17 e⁻) gains 1 → 18 e⁻

Step1: NaCl ratio and bonding

NaCl is 1:1 ionic (Na⁺ + Cl⁻). Need element forming -1 ion (like Cl⁻).

Step2: Analyze options

(A) K: Group 1 (loses 1 → +1; forms NaK? No, metal-metal)
(B) Mg: Group 2 (loses 2 → +2; ratio 2:1)
(C) Ar: Noble gas (inert)
(D) Br: Group 17 (gains 1 → -1; forms NaBr 1:1 ionic)

Step1: Interpret PES peaks

3 peaks → 3 electron shells/subshells. Lowest binding energy peak = valence electrons.

Step2: Match with atomic model

Valence electrons determine ion charge. If valence peak has 1 electron, element loses 1 → +1 charge.

Step3: Check options

(C) Ions with +1 charge aligns with 1 valence electron (consistent with PES peaks).

Answer:

(B) Sr²⁺