Which type of radiation emits helium ions and can be stopped by a piece of paper?

Correct Answer: B

Rationale: Alpha radiation emits helium ions, which are helium nuclei without electrons, making them positively charged. These ions are relatively large and heavy compared to beta and gamma radiation. Due to their size and charge, alpha particles interact strongly with matter and are easily stopped. A piece of paper or even human skin can effectively block alpha radiation. Therefore, alpha radiation is the type of radiation that can be stopped by a piece of paper. Beta radiation consists of fast-moving electrons and can penetrate further into materials than alpha radiation, thus not stopped by a piece of paper. Gamma radiation is highly penetrating and requires dense materials like lead or concrete to block it effectively. X-ray radiation, similar to gamma radiation, is also highly penetrating and cannot be stopped by a piece of paper.

Correct Answer: B

Rationale: The correct answer is B: "-2". Oxygen usually exhibits an oxidation state of -2 in most compounds. This is due to oxygen's high electronegativity, which causes it to attract electrons, leading to the gain of two electrons in chemical reactions. Choice A (-1) is incorrect because oxygen rarely has an oxidation state of -1 in compounds. Choice C (0) is incorrect as oxygen does not usually have an oxidation state of zero in compounds. Choice D (-3) is incorrect as oxygen does not commonly have an oxidation state of -3 in compounds.

Correct Answer: B

Rationale: A balanced equation is one where the number of each type of atom is the same on both sides, fulfilling the law of conservation of mass. This principle ensures that the total number of atoms of each element is equal in both reactants and products, signifying that no atoms are created or destroyed, but rather rearranged. Choice A is incorrect because a balanced equation has equal numbers of atoms in the reactants and products. Choice C is incorrect as a balanced equation includes both reactants and products. Choice D is incorrect because coefficients are essential in balancing equations by adjusting the number of atoms present.

Correct Answer: A

Rationale: The correct answer is A: Covalent. Covalent bonds involve a complete sharing of electrons between atoms, typically atoms that have partially filled outer shells or energy levels. This sharing of electron pairs results in a stable configuration for both atoms involved in the bond. For example, diamond is strong because it involves a vast network of covalent bonds between the carbon atoms in its structure. Choice B, Hydrogen bonds, involve a partial sharing of hydrogen atoms rather than a complete sharing of electrons. Choice C, Proportional bonds, is not a recognized term in chemistry. Choice D, N/A, is not a valid option for this question.

Correct Answer: C

Rationale: The correct answer is C: Ionic. When elements with low electronegativity (almost empty outer shells) react with elements with high electronegativity (mostly full outer shells), they tend to transfer electrons from the low electronegative element to the high electronegative element. This transfer results in the formation of ionic bonds, where one element becomes positively charged (cation) and the other element becomes negatively charged (anion). Ionic bonds are formed through the attraction between these opposite charges, leading to a strong bond between the two elements. Choice A, Hydrogen, is incorrect because hydrogen is not involved in the described electron transfer process to form ionic bonds. Choice B, Covalent, is incorrect because covalent bonds involve the sharing of electrons between atoms, not the transfer of electrons as seen in the formation of ionic bonds. Choice D, Nuclear, is incorrect as nuclear bonds are not a recognized type of chemical bond. Therefore, the most appropriate answer is C: Ionic bonds.