the energy required to remove the outermost electron from an atom is called
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HESI A2

HESI A2 Chemistry

1. What is the energy required to remove the outermost electron from an atom called?

Correct answer: D

Rationale: Ionization energy is the energy needed to remove the outermost electron from an atom, resulting in the formation of a positively charged ion. The higher the ionization energy, the more difficult it is to extract an electron. Electronegativity, however, measures an atom's ability to attract shared electrons in a chemical bond. Atomic radius refers to the distance from the nucleus to the outermost electron. Covalent bonding involves sharing electron pairs between atoms to create a stable bond. Therefore, the correct answer is ionization energy as it specifically relates to the energy needed to remove an electron from an atom.

2. Aluminum (Al) has 13 protons in its nucleus. What is the number of electrons in an Al3+ ion?

Correct answer: C

Rationale: Aluminum (Al) has an atomic number of 13, which indicates it normally has 13 electrons to balance the 13 protons in its nucleus. When Al forms an Al3+ ion, it loses 3 electrons to achieve a stable electron configuration. Therefore, the Al3+ ion will have 13 - 3 = 10 electrons. Choice A (16) is incorrect as it doesn't take into account the charge of the Al3+ ion. Choice B (13) is incorrect because the Al3+ ion has lost electrons. Choice D (3) is incorrect as it doesn't reflect the total number of electrons lost by the Al atom to form the Al3+ ion.

3. What is the oxidation state of the chlorine atom in the compound HCl?

Correct answer: B

Rationale: In the compound HCl (hydrochloric acid), the hydrogen atom has an oxidation state of +1 based on the rules of assigning oxidation states. Since the overall compound is neutral, the oxidation state of chlorine must be -1 to balance the charge. Chlorine typically has an oxidation state of -1 in binary compounds with nonmetals, such as HCl. Therefore, the correct answer is -1. Choices A, C, and D are incorrect as the oxidation state of chlorine in HCl is -1, not +1, +2, or -2.

4. What are the three types of radiation?

Correct answer: A

Rationale: The correct answer is Alpha, beta, gamma. Alpha radiation consists of helium nuclei, beta radiation comprises electrons or positrons, and gamma radiation is high-energy electromagnetic radiation. Choice B, delta, is incorrect as delta is not a type of radiation. Choice C, gamma, delta, epsilon, and Choice D, beta, gamma, epsilon, are incorrect as they do not include the three standard types of radiation.

5. How can water be boiled at room temperature?

Correct answer: A

Rationale: The boiling point of water is directly affected by pressure. By lowering the pressure, water can boil at a lower temperature, even at room temperature. This occurs because at lower pressures, the molecules of water have less resistance to escaping into the vapor phase, thus enabling boiling to occur at lower temperatures. Choices B, C, and D are incorrect because increasing the pressure, decreasing the volume, or raising the boiling point would actually require higher temperatures to boil water rather than achieving boiling at room temperature.

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