Chemistry Hesi A2 - Nurselytic

Correct Answer: B

Rationale: Noble gases are non-polar molecules without a permanent dipole moment. The only intermolecular force applicable to noble gases is the London dispersion force, also known as Van der Waals forces. This force is a temporary attractive force resulting from the formation of temporary dipoles in non-polar molecules. Dipole-dipole interactions, Keesom interactions, and hydrogen bonding involve significant dipoles or hydrogen atoms bonded to electronegative atoms, which do not apply to noble gases.

Correct Answer: A

Rationale: The correct answer is NaCl (sodium chloride). Ionic compounds are formed by the transfer of electrons between a metal and a nonmetal. In NaCl, sodium (Na) is a metal, and chlorine (Cl) is a nonmetal. Sodium donates an electron to chlorine, leading to the formation of the ionic bond between them. This results in the formation of an ionic compound, where positively charged sodium ions are attracted to negatively charged chloride ions, creating a crystal lattice structure.

Choices B, C, and D are not ionic compounds. H₂O (water) is a covalent compound formed by the sharing of electrons between two nonmetals (oxygen and hydrogen). HCl (hydrogen chloride) and NH₃ (ammonia) are also covalent compounds involving nonmetals sharing electrons, not transferring them.

Correct Answer: B

Rationale: In the compound NH3, nitrogen is bonded to three hydrogen atoms. Hydrogen is always assigned an oxidation state of +1. Since the overall charge of NH3 is zero, the oxidation state of nitrogen must be -1 to balance out the hydrogen's +1 oxidation state.
Therefore, the correct oxidation state of the nitrogen atom in NH3 is -1.
Choice A (-3) is incorrect because it does not account for the electronegativity of hydrogen.
Choice C (+1) and
Choice D (+3) are incorrect as the nitrogen atom in NH3 needs to balance the +1 oxidation state of each hydrogen atom, resulting in a total of -3 to maintain the compound's charge neutrality.

Correct Answer: C

Rationale: Atoms with the largest atomic radius are located at the bottom of their group on the periodic table. This is because atomic radius increases down a group due to the addition of more energy levels or shells of electrons. As you move down a group, the outermost electrons are further away from the nucleus, leading to an increase in atomic radius.
Choice A 'At the top of their group' is incorrect because atomic radius decreases going up within a group.
Choice B 'In the middle of their group' is incorrect as the atomic radius generally increases as you go down a group, not in the middle.
Choice D 'Along the right-hand side' is incorrect because atomic radius tends to decrease from left to right across a period on the periodic table due to increased nuclear charge and effective nuclear charge.

Correct Answer: B

Rationale: The atomic number of neon is 10, which represents the number of protons in its nucleus. In a neutral atom, the number of electrons is equal to the number of protons to maintain electrical neutrality.
Therefore, a neutral atom of neon contains 10 electrons, matching the 10 protons within the nucleus.
Choice A (9 electrons) is incorrect as it doesn't correspond to the atomic number of neon.

Choices C (11 electrons) and D (12 electrons) are also incorrect as they do not align with the correct atomic number of neon.