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: The correct answer is C: Several feet of concrete. Gamma radiation is highly penetrating and requires dense materials to effectively block it. Concrete, being a dense material, can absorb and block gamma radiation effectively due to its high atomic number and thickness. Aluminum foil (A) and glass (B) are not dense enough to stop gamma radiation. Paper (D) is too thin and lacks the density needed to block gamma radiation effectively.

Correct Answer: C

Rationale: Alpha particles are positively charged and relatively large, so they have low penetrating power. A piece of paper can stop alpha particles because the paper's thickness provides enough material for the particles to collide with and lose their energy through ionization. Aluminum foil and glass are not thick enough to effectively stop alpha particles. Plastic, depending on its thickness, may not provide sufficient shielding to stop alpha particles completely. In summary, the correct answer is C because the thickness of a piece of paper is sufficient to stop alpha particles, while the other choices are not adequate for effective shielding.

Correct Answer: B

Rationale: The correct answer is B: By their chemical properties. The periodic table arranges elements based on their atomic number, which determines their chemical properties. Elements in the same column have similar properties due to their shared electron configurations. This organization helps predict an element's behavior in chemical reactions. Choices A, C, and D are incorrect because atomic mass, physical state, and charge do not determine an element's position in the periodic table or its relationship to other elements.

Correct Answer: C

Rationale: The correct answer is C: Electronegativity. Polarity in a molecule is determined by the difference in electronegativity between atoms forming a bond. The greater the electronegativity difference, the more polar the bond and molecule. This is because electronegativity measures an atom's ability to attract electrons towards itself. Bond length (A) and bond strength (B) do not directly determine polarity, although shorter and stronger bonds can influence polarity indirectly. Molecular weight (D) is not a factor in determining polarity, as it relates to the total mass of a molecule rather than its polarity.