Bromine exists naturally as a mixture of bromine-79 and bromine-81 isotopes. An atom of bromine-79 contains

Correct Answer: A

Rationale: The correct answer is A because Bromine-79 has an atomic number of 35, indicating the number of protons. Neutrons are calculated by subtracting the atomic number from the mass number, so Bromine-79 with a mass number of 79 has 44 neutrons. Electrons are equal to the number of protons in a neutral atom, so there are 35 electrons in an atom of Bromine-79. Choice B is incorrect because it does not account for the correct number of neutrons present in Bromine-79. Choice C is incorrect as it has an incorrect number of protons and electrons for Bromine-79. Choice D is incorrect as it incorrectly assigns 79 neutrons to Bromine-79, which is the total mass number, not the number of neutrons.

Correct Answer: C

Rationale: The correct answer is C: Mg2+. A species with 12 protons must have an atomic number of 12, which corresponds to magnesium (Mg). The 10 electrons indicate that it has a 2+ charge, making it Mg2+. Choice A (Ne2+) is incorrect because neon (Ne) has an atomic number of 10, not 12. Choice B (Ti2+) is incorrect because titanium (Ti) has an atomic number of 22, not 12. Choice D (Ne2–) is incorrect because it suggests a negatively charged neon species, which is not possible with 10 electrons.

Correct Answer: A

Rationale: The correct answer is A: By either adding or subtracting protons from the atom. An ion is formed when an atom gains or loses electrons, leading to an unequal number of protons and electrons. Protons determine the atom's identity, so changing the number of protons would result in a different element. This process results in the formation of ions with a positive charge if protons are added or a negative charge if protons are subtracted. Choices B and C are incorrect because adding or subtracting electrons or neutrons does not change the fundamental identity of the atom, only its charge or mass. Choice D is incorrect as not all options are true for ion formation.

Correct Answer: B

Rationale: The correct answer is B because changing the number of protons in an atom's nucleus would result in a different element, not an ion. A: True - adding or removing electrons forms ions. C: True - removing electrons forms positively charged ions. D: True - ions have a charge due to the imbalance of protons and electrons.