What is the correct electron configuration for lithium?

Correct Answer: A

Rationale: The electron configuration for lithium is 1s²2s¹. Lithium has 3 electrons, and the configuration indicates that the first two electrons fill the 1s orbital, while the third electron fills the 2s orbital. Therefore, the correct electron configuration for lithium is 1s²2s¹. Choice B (1s²2s²) is incorrect as it represents the electron configuration for beryllium, not lithium. Choice C (1s²2s¹2p¹) includes the 2p orbital, which is not involved in lithium's electron configuration. Choice D (1s¹2s¹2p²) is incorrect as it does not accurately represent lithium's electron configuration.

Correct Answer: D

Rationale: In water solutions of bases, the dominant ion would be OH⁻ (hydroxide ion). Bases release OH⁻ ions when dissolved in water, increasing the concentration of hydroxide ions and leading to a higher pH. This is in contrast to acids, which release H⁺ ions. Therefore, in water solutions of bases, the presence of OH⁻ ions signifies the basic nature of the solution. Choices A, B, and C are incorrect because MgCl₂ is a salt, 2HCl is a compound consisting of two hydrogen ions and one chloride ion, and H⁺ represents a hydrogen ion typically associated with acids, not bases.

Correct Answer: B

Rationale: The molar mass of water (Hâ‚‚O) is calculated by adding the atomic masses of two hydrogen atoms (each with a molar mass of approximately 1 g/mol) and one oxygen atom (with a molar mass of approximately 16 g/mol). Therefore, the molar mass of water is approximately 18 g/mol, making choice B the correct answer. Choice A (16 g/mol) is incorrect because it represents the molar mass of oxygen, not water. Choices C (20 g/mol) and D (22 g/mol) are incorrect as they do not correspond to the molar mass of water.

Correct Answer: C

Rationale: An alpha particle consists of two protons and two neutrons, resulting in a total charge of +2 due to the presence of two positively charged protons. Therefore, the correct answer is C, indicating a charge of +2. Choices A, B, and D are incorrect because an alpha particle is positively charged due to the two protons it contains, resulting in a charge of +2.

Correct Answer: D

Rationale: The correct name for AgNO₃ is silver nitrate. In chemical nomenclature, the element symbol Ag represents silver, and the polyatomic ion NO₃ is known as nitrate. Therefore, when the silver ion (Ag⁺) combines with the nitrate ion (NO₃⁻), the resulting compound is named silver nitrate (AgNO₃). Choices A, B, and C are incorrect because they do not accurately represent the composition of AgNO₃. Argent nitrous (Choice A) and Argent oxide (Choice B) do not reflect the correct anion, and Silver nitrite (Choice C) uses a different anion altogether.