HESI A2 Chemistry Questions

Correct Answer: A

Rationale: The correct answer is A: Covalent bond. In a covalent bond, two atoms share electrons to complete their outer electron shells and achieve stability. This sharing results in a strong bond between the atoms. Ionic bonds involve the transfer of electrons, metallic bonds involve a "sea" of shared electrons in a metal lattice, and hydrogen bonds are weaker interactions between a hydrogen atom and an electronegative atom. Covalent bonds are the only option where electrons are shared between atoms to form a stable bond.

Correct Answer: B

Rationale: The correct answer is B: Na. Sodium's chemical symbol is Na because it is derived from its Latin name "natrium." N represents nitrogen, Cl represents chlorine, and H represents hydrogen, making them incorrect choices. Remember to consider the element's name origins for accurate symbol identification.

Correct Answer: B

Rationale: The correct answer is B: periods. Periods are the horizontal rows in the periodic table that represent the energy levels of the elements. They indicate the number of electron shells present in an element. Groups (A) are the vertical columns, representing elements with similar chemical properties. Families (C) are also vertical columns that share similar characteristics. Sets (D) is a generic term and not specific to the periodic table structure. Therefore, the correct term for the horizontal rows of the periodic table is periods.

Correct Answer: A

Rationale: The mass number is the sum of protons and neutrons in an atom. Given 6 protons and 6 neutrons, the mass number would be 6+6=12. Electrons do not contribute significantly to the mass number. Therefore, the correct answer is A: 12. Choice B is incorrect as it adds the protons, neutrons, and electrons together. Choice C only considers the number of protons. Choice D is incorrect as it only includes the number of protons.

Correct Answer: D

Rationale: The correct answer is D: hydriodic acid. In aqueous solution, HI dissociates into H+ and I- ions, forming hydriodic acid. Choice A (hydroiodic acid) is incorrect as it does not reflect the presence of water in the compound. Choice B (hydrogen monoiodide) is incorrect as it incorrectly implies the presence of only one iodide ion. Choice C (hydrogen iodide) is incorrect as it does not specify the compound in aqueous solution. Therefore, the correct term for aqueous HI is hydriodic acid.