Question

1. which statement concerning ⁷⁹₃₄ se and ⁷⁹₃₅ br is true? a. ⁷⁹₃₄ se has more protons per atom than ⁷⁹₃₅ br. b. ⁷⁹₃₄ se has more neutrons per atom than ⁷⁹₃₅ br. c. both ⁷⁹₃₄ se and ⁷⁹₃₅ br contain the same number of neutrons per atom. d. both ⁷⁹₃₄ se and ⁷⁹₃₅ br contain the same number of electrons per atom.

Explanation:

Step1: Recall atomic - number and mass - number concepts

The notation $^{A}_{Z}X$ represents an atom, where $A$ is the mass number (number of protons + neutrons) and $Z$ is the atomic number (number of protons). For $^{79}_{34}Se$, the atomic number $Z = 34$ and mass number $A = 79$. For $^{79}_{35}Br$, the atomic number $Z = 35$ and mass number $A = 79$.

Step2: Calculate number of neutrons

The number of neutrons $N=A - Z$. For $^{79}_{34}Se$, $N_{Se}=79 - 34=45$. For $^{79}_{35}Br$, $N_{Br}=79 - 35 = 44$.

Step3: Analyze number of electrons

In a neutral atom, the number of electrons is equal to the number of protons. For $^{79}_{34}Se$, the number of protons is 34, so the number of electrons is 34. For $^{79}_{35}Br$, the number of protons is 35, so the number of electrons is 35.

Step4: Evaluate each option

• Option A: $^{79}_{34}Se$ has 34 protons and $^{79}_{35}Br$ has 35 protons. So $^{79}_{34}Se$ has fewer protons than $^{79}_{35}Br$, not more.
• Option B: $^{79}_{34}Se$ has 45 neutrons and $^{79}_{35}Br$ has 44 neutrons. So $^{79}_{34}Se$ has more neutrons per atom than $^{79}_{35}Br$.
• Option C: The number of neutrons in $^{79}_{34}Se$ is 45 and in $^{79}_{35}Br$ is 44, so they do not have the same number of neutrons per atom.
• Option D: The number of electrons in $^{79}_{34}Se$ is 34 and in $^{79}_{35}Br$ is 35, so they do not have the same number of electrons per atom.

Answer:

B. $^{79}_{34}Se$ has more neutrons per atom than $^{79}_{35}Br$.