Which particles are emitted during radioactivity?

Correct Answer: C

Rationale: During radioactivity, radiation is emitted from an unstable nucleus. This radiation can take various forms like alpha particles, beta particles, or gamma rays. These particles or rays are emitted as a result of the unstable nucleus's attempt to achieve a more stable configuration. Therefore, the correct answer is radiation (Choice C). Electrons (Choice A), protons (Choice B), and neutrons (Choice D) are not typically emitted during radioactivity, as the emission is primarily in the form of radiation.

Correct Answer: B

Rationale: The correct answer is 'Single replacement.' In a single replacement reaction, an active metal replaces another element in an ionic compound, resulting in the formation of a new compound. Option A, 'Combustion,' involves a substance rapidly reacting with oxygen to release energy in the form of heat and light. Option C, 'Synthesis,' involves the combination of two or more substances to form a more complex product. Option D, 'Decomposition,' involves the breakdown of a compound into simpler substances.

Correct Answer: B

Rationale: Dispersion forces, also known as London dispersion forces, are the weakest intermolecular forces that occur in non-polar covalent compounds. These forces result from temporary shifts in electron density within molecules, creating temporary dipoles. As a result, non-polar molecules, which lack a permanent dipole moment, can experience these dispersion forces. Polar compounds exhibit stronger intermolecular forces such as dipole-dipole interactions or hydrogen bonding, while ionic compounds involve electrostatic interactions between ions. Therefore, the correct answer is non-polar (choice B). Choices A, C, and D are incorrect because dispersion forces are typically found in non-polar covalent compounds, not polar, ionic, or hydrogen-bonded compounds.

Correct Answer: A

Rationale: Group IA elements, also known as alkali metals, have a +1 charge. They readily lose one electron to achieve a stable electron configuration, forming ions with a single positive charge. This makes +1 the correct choice. Choices B, C, and D are incorrect because alkali metals in Group IA typically lose one electron, so they do not have a +2, +3, or 0 charge.

Correct Answer: C

Rationale: Beta radiation particles are high-energy, fast-moving electrons or positrons. Aluminum foil is effective in stopping beta radiation due to its ability to absorb and block these particles. When beta particles interact with the aluminum foil, they lose energy and are absorbed, preventing their penetration. Plastic and glass are not as effective as aluminum foil in stopping beta radiation. While concrete provides some shielding against beta particles, aluminum foil is a more suitable material for this purpose as it offers better absorption and blocking capabilities.

Correct Answer: D

Rationale: The mass of one mole of a substance is represented by its molar mass. Molar mass is the mass of one mole of a substance and is expressed in grams per mole. It is calculated by summing the atomic masses of all atoms in a molecule. Therefore, the correct answer is D - 'Molar mass'. Choice A, 'Atomic mass', refers to the average mass of an atom of an element. Choice B, 'Mass number', is the total number of protons and neutrons in an atom's nucleus. Choice C, 'Molecular weight', is the average mass of a molecule relative to 1/12 of the mass of an atom of carbon-12.

Correct Answer: B

Rationale: The sum of protons and neutrons in an element is known as the mass number. The mass number is an important concept in chemistry as it represents the total number of nucleons (protons and neutrons) in an atom's nucleus. It is different from the atomic number, which represents the number of protons in an atom. The atomic mass is the average mass of an element's isotopes, taking into account the abundance of each isotope. Neutron number, on the other hand, specifically refers to the number of neutrons in an atom's nucleus. Therefore, the correct answer is B, mass number.

Correct Answer: C

Rationale: Negatively charged ions are called anions. Anions gain electrons and carry a negative charge, which distinguishes them from cations that are positively charged and neutrons and protons that are subatomic particles found in the nucleus of an atom. Choice A, Neutrons, are neutral subatomic particles found in the nucleus of an atom, not negatively charged ions. Choice B, Protons, are positively charged subatomic particles found in the nucleus of an atom, not negatively charged ions. Choice D, Cations, are positively charged ions that lose electrons, which is opposite to the behavior of negatively charged ions.

Correct Answer: C

Rationale: An ionic bond forms when one atom transfers electrons to another, resulting in the formation of positively and negatively charged ions. The attraction between these oppositely charged ions creates an electrostatic bond, known as an ionic bond. Choice A, covalent bonds, involve the sharing of electrons, not the transfer. Choice B, metallic bonds, occur between metal atoms and involve a 'sea of electrons' that are delocalized. Choice D, hydrogen bonds, are much weaker interactions between hydrogen atoms and other electronegative atoms like oxygen or nitrogen.