What can stop the penetration of gamma radiation?

Correct Answer: C

Rationale: Gamma radiation is highly penetrative and requires dense materials to block it effectively. While aluminum foil and glass are not sufficient to stop gamma radiation, several feet of concrete is needed due to its high density and ability to absorb gamma radiation effectively. A piece of paper is too thin and lacks the density required to block gamma radiation, making it an ineffective shield.

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.

Correct Answer: A

Rationale: In a single bond between two atoms, only one pair of electrons is shared. This is because a single covalent bond involves the sharing of two electrons, one from each participating atom. Therefore, option A (1) is the correct answer. Option B (2) is incorrect because two pairs of electrons shared between two atoms would form a double bond, not a single bond. Double bonds are characterized by the sharing of four electrons (two pairs). Option C (3) is incorrect as well because three pairs of electrons shared would indicate a triple bond, which is even stronger and involves the sharing of six electrons (three pairs) between the two atoms. Option D (4) is also incorrect as it suggests the sharing of four pairs of electrons, which is not characteristic of a single bond. Understanding the number of electron pairs shared in different types of chemical bonds is crucial in chemistry as it influences the strength and properties of the bond. This knowledge is fundamental in understanding molecular structures, reactivity, and various chemical processes.

Correct Answer: B

Rationale: The correct answer is B. In a double covalent bond, two pairs of electrons are shared between two atoms. This sharing of two electron pairs results in a stronger bond compared to a single covalent bond where only one pair of electrons is shared. Choice A is incorrect because a single covalent bond involves the sharing of one pair of electrons. Choices C and D are incorrect as they do not represent the correct number of electron pairs shared in a double covalent bond.

Correct Answer: C

Rationale: The correct answer is C. In a triple covalent bond, three pairs of electrons are shared between two atoms. This sharing results in a total of six electrons being shared, making the bond strong. Choice A (1) is incorrect because a single covalent bond involves the sharing of one pair of electrons. Choice B (2) is incorrect as a double covalent bond consists of the sharing of two pairs of electrons. Choice D (4) is incorrect because there are only three pairs of electrons shared in a triple covalent bond, not four.