HESI A2
HESI A2 Chemistry Practice Questions
1. What is the correct electron configuration for nitrogen?
- A. 1s² 2s²
- B. 1s² 2s² 2p²
- C. 1s² 2s² 2p³
- D. 1s² 2s² 2p⁴
Correct answer: C
Rationale: The electron configuration of nitrogen is determined by its atomic number, which is 7. Nitrogen has 7 electrons. Following the order of filling orbitals, the electron configuration for nitrogen is 1s² 2s² 2p³. This means the first energy level is filled with 2 electrons in the 1s orbital, the second energy level is filled with 2 electrons in the 2s orbital, and 3 electrons in the 2p orbital. Each orbital can hold a specific number of electrons, and nitrogen, with its 7 electrons, fits this configuration. Choice A is incorrect because it does not account for all the electrons in the nitrogen atom. Choice B is incorrect as it only represents 6 electrons, not the 7 electrons in nitrogen. Choice D is incorrect as it represents 8 electrons, which is not the correct electron configuration for nitrogen.
2. Which element has the highest atomic number?
- A. Uranium
- B. Hydrogen
- C. Radon
- D. Bismuth
Correct answer: A
Rationale: The correct answer is Uranium. The atomic number represents the number of protons in an atom's nucleus. Among the options provided, Uranium has the highest atomic number, which is 92. Hydrogen has an atomic number of 1, Radon has an atomic number of 86, and Bismuth has an atomic number of 83. Therefore, Uranium is the element with the highest atomic number in the given choices.
3. How many neutrons does carbon-14 have?
- A. 10
- B. 8
- C. 6
- D. 12
Correct answer: B
Rationale: The correct answer is B: 8. Carbon-14 is an isotope of carbon with 6 protons and 8 neutrons. To determine the number of neutrons in an atom, subtract the atomic number (number of protons) from the mass number. In this case, the mass number of carbon-14 is 14, and the atomic number of carbon is 6. Therefore, 14 (mass number) - 6 (atomic number) = 8 neutrons. Choices A, C, and D are incorrect because they do not reflect the correct number of neutrons in a carbon-14 atom.
4. What is the chemical symbol for sodium?
- A. N
- B. Na
- C. Cl
- D. H
Correct answer: B
Rationale: The correct chemical symbol for sodium is 'Na.' In the periodic table, sodium is represented by the symbol 'Na,' derived from its Latin name 'natrium.' The symbol 'N' represents nitrogen, not sodium. 'Cl' is the symbol for chlorine, and 'H' is the symbol for hydrogen. Therefore, 'Na' is the correct chemical symbol for sodium.
5. Which intermolecular force is the strongest?
- A. Dipole interactions
- B. Dispersion forces
- C. Hydrogen bonding
- D. Van der Waals forces
Correct answer: C
Rationale: Hydrogen bonding is the strongest intermolecular force due to its specific interaction between a hydrogen atom and a highly electronegative atom like nitrogen, oxygen, or fluorine. This type of bonding results in a very strong attraction between molecules, making it the strongest intermolecular force among the options provided. Dipole interactions (choice A) are weaker than hydrogen bonding as they occur between polar molecules. Dispersion forces (choice B) are the weakest intermolecular forces and are caused by temporary fluctuations in electron distribution. Van der Waals forces (choice D) are a broader term that encompasses dipole interactions and dispersion forces, making them weaker than hydrogen bonding.
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