Chemistry HESI A2 Quizlet

Correct Answer: C

Rationale: The correct answer is C, atomic number. The atomic number represents the number of protons in an element. This is because the atomic number is the unique identifier of an element and determines its chemical properties. Protons are the positively charged particles in the nucleus of an atom, and the number of protons defines the element's identity. Explanation for incorrect choices: A: Atomic mass represents the average mass of all isotopes of an element, not the number of protons. B: Mass number is the sum of protons and neutrons in an atom, not just the number of protons. D: "Proton number" is not a standard term in chemistry, and it does not specifically refer to the number of protons in an element.

Correct Answer: C

Rationale: Increasing the surface area of a reactant increases the number of exposed particles available for collision, leading to more frequent and successful collisions. This results in an increased reaction rate. Choice A is incorrect because more surface area facilitates faster reactions. Choice B is incorrect as surface area affects reaction rate. Choice D is incorrect as increasing surface area does not stop the reaction; it actually accelerates it.

Correct Answer: A

Rationale: The correct answer is A: Polar. In a covalent bond, if electrons are not shared equally, the bond is considered polar. This occurs when one atom has a higher electronegativity than the other, leading to an uneven distribution of electron density. As a result, one end of the bond will have a partial negative charge while the other end will have a partial positive charge, creating a dipole moment. Choices B (Non-polar) and D (Hydrogen) are incorrect because they do not specifically address the unequal sharing of electrons in a covalent bond. Choice C (Ionic) is incorrect as ionic bonds involve the complete transfer of electrons, not sharing.

Correct Answer: B

Rationale: The correct answer is B: Chemical reaction. In a chemical reaction, bonds are broken and new bonds are formed to create new chemical compounds. The process involves the rearrangement of atoms to form different substances with unique properties. Physical reactions (choice A) involve changes in physical state or appearance without altering the chemical composition. Nuclear reactions (choice C) involve changes in the nucleus of an atom, leading to the formation of different elements. Mechanical reactions (choice D) involve physical forces but do not result in the formation of new chemical compounds.

Correct Answer: C

Rationale: The columns of the periodic table are called "Groups" because elements within the same group share similar chemical properties due to having the same number of valence electrons. Each group is designated by a number and a letter, indicating the number of valence electrons. Periods refer to the rows of the periodic table, representing the number of electron shells an element has. Families is a more colloquial term used to describe groups of elements with similar properties. Rows refer to the horizontal rows of the periodic table. Therefore, the correct answer is C as it specifically refers to the vertical columns in the periodic table that share similar chemical properties.