which gives the number of protons in the atomic nucleus of an alkali metal

HESI A2

Chemistry HESI A2 Practice Test

1. What is the number of protons in the atomic nucleus of an alkali metal?

A. 9
B. 10
C. 11
D. 12

Correct answer: C

Rationale: The number of protons in the atomic nucleus of an alkali metal is 11. Alkali metals, belonging to group 1 of the periodic table, have 1 electron in their outer shell, which corresponds to 1 proton in their nucleus. Therefore, the correct answer is option C: 11. Choice A (9) is incorrect because it does not match the number of protons in an alkali metal. Choice B (10) is incorrect as it is also not the correct number of protons for an alkali metal. Choice D (12) is incorrect as it is not the typical number of protons found in the nucleus of an alkali metal.

2. What is the mass number of an atom with 6 protons, 6 neutrons, and 6 electrons?

A. 12
B. 18
C. 6
D. 8

Correct answer: A

Rationale: The mass number of an atom is the sum of protons and neutrons. In this case, the atom has 6 protons and 6 neutrons, thus the mass number is 6 + 6 = 12. Therefore, choice A (12) is the correct answer. Choices B (18), C (6), and D (8) are incorrect because the mass number is determined by the sum of protons and neutrons, not the number of electrons or a different combination of particles.

3. Which type of radiation involves the emission of helium ions?

A. Beta
B. Alpha
C. Gamma
D. Delta

Correct answer: B

Rationale: Alpha radiation involves the emission of helium ions. Helium ions are composed of two protons and two neutrons, which is the same as the nucleus of a helium atom. This type of radiation has low penetration power and can be stopped by a piece of paper or human skin, making it less harmful compared to other forms of radiation like beta or gamma radiation. Beta radiation involves the emission of high-speed electrons, while gamma radiation involves electromagnetic waves with high energy. Delta radiation is not a recognized form of radiation in this context, making it an incorrect choice.

4. What is the name of the bond formed when two atoms share electrons?

A. Covalent bond
B. Ionic bond
C. Metallic bond
D. Hydrogen bond

Correct answer: A

Rationale: A covalent bond is formed when two atoms share electrons, creating a stable electron configuration. This sharing allows both atoms to achieve a full outer shell of electrons, leading to a stable molecule. In contrast, an ionic bond involves the transfer of electrons from one atom to another, resulting in the formation of ions with opposite charges. Metallic bonds are formed between metal atoms and involve a 'sea of electrons' that are delocalized and free to move. Hydrogen bonds are a type of intermolecular force, not a true chemical bond, and occur between a hydrogen atom and a highly electronegative atom like oxygen or nitrogen.

5. What is the pH of a neutral solution?

A. 7
B. 0
C. 14
D. 4

Correct answer: A

Rationale: The correct answer is A: 7. A neutral solution has a pH of 7. In the pH scale, values below 7 are acidic, 7 is neutral, and values above 7 are basic. Therefore, a solution with a pH of 7 is considered neutral as it is neither acidic nor basic. Choices B, C, and D are incorrect because a pH of 0 indicates a strong acid, a pH of 14 indicates a strong base, and a pH of 4 indicates an acidic solution. None of these values represent a neutral solution.