Chemistry HESI A2 Quizlet

Correct Answer: B

Rationale: The correct answer is B: +2. Group IIA elements have a valence of +2 because they have 2 valence electrons in their outer shell. These elements lose these 2 electrons to achieve a stable octet configuration, resulting in a +2 charge. Choice A is incorrect because Group IIA elements do not have a charge of 1. Choice C is incorrect because Group IIA elements do not typically have a negative charge of -3. Choice D is incorrect because Group IIA elements do not have a charge of 0; they lose 2 electrons to become positively charged.

Correct Answer: B

Rationale: The correct answer is B: Physical. When no change is made to the chemical composition of a substance, it indicates a physical change. In physical changes, the substance retains its chemical identity and only its physical properties, such as shape, size, and state, are altered. This is because the particles in the substance rearrange or move without forming new substances. Choice A (Chemical) involves a change in the chemical composition, so it is incorrect. Choice C (Nuclear) involves changes at the atomic level, leading to different elements, which is not the case here. Choice D (Mechanical) involves changes in position and motion of objects, not relevant to the chemical composition of a substance.

Correct Answer: B

Rationale: The sum of protons and neutrons in an element represents the mass number. Protons and neutrons are located in the nucleus and contribute to the mass of an atom. The atomic number (A) is the number of protons in an atom, not the sum of protons and neutrons. Atomic mass (C) is the average mass of an element's isotopes, considering their abundance, and is not the sum of protons and neutrons. Neutron number (D) refers to the specific number of neutrons in an atom, not the total mass of the nucleus. Therefore, the correct answer is B, as it accurately represents the total mass of an atom.

Correct Answer: C

Rationale: The correct answer is C: Element. An element is the simplest form of a substance that cannot be broken down further by chemical means. It consists of only one type of atom. Compounds (A) are made up of two or more different types of atoms chemically bonded. Mixtures (B) contain two or more substances physically mixed but not chemically bonded. Molecules (D) are combinations of atoms, which can be either elements or compounds.

Correct Answer: D

Rationale: The correct answer is D because fluorine, oxygen, and nitrogen are typically involved in hydrogen bonding due to their high electronegativity, which allows them to form strong partial charges. This creates a polar covalent bond with hydrogen, leading to hydrogen bonding. Fluorine, chlorine, and oxygen (Choice B) are incorrect as chlorine is not typically involved. Carbon, hydrogen, and oxygen (Choice A) lack the necessary electronegativity for hydrogen bonding. Fluorine, chlorine, and nitrogen (Choice C) also lack the required electronegativity for effective hydrogen bonding. In summary, only elements with high electronegativity like fluorine, oxygen, and nitrogen are typically involved in hydrogen bonding.