A species with 12 protons and 10 electrons is

Correct Answer: C

Rationale: The correct answer is C: Mg2+. A species with 12 protons must have an atomic number of 12, which corresponds to magnesium (Mg). The 10 electrons indicate that it has a 2+ charge, making it Mg2+. Choice A (Ne2+) is incorrect because neon (Ne) has an atomic number of 10, not 12. Choice B (Ti2+) is incorrect because titanium (Ti) has an atomic number of 22, not 12. Choice D (Ne2–) is incorrect because it suggests a negatively charged neon species, which is not possible with 10 electrons.

Correct Answer: B

Rationale: The correct answer is B (5 significant figures) because leading zeros are not considered significant. In the number 04560700, the zeros before the 4 are placeholders and do not add to the precision of the number. Therefore, only the digits 4, 5, 6, 0, and 7 are significant. Choice A (4) is incorrect because it does not account for the zeros after the 6. Choice C (7) is incorrect as it counts all the digits including the leading zeros. Choice D (8) is incorrect as it includes all the digits, including non-significant zeros.

Correct Answer: B

Rationale: The correct answer is B: $2.20 /gal. To convert the price of London petrol given in British pounds to dollars per gallon, we first need to convert the price from pounds to dollars using the current exchange rate. Then, we convert the price per liter to price per gallon by multiplying by the conversion factor (1 gal = 3.7854 L). The conversion results in $2.20 /gal. Choice A ($4.46 /gal) is incorrect because it is not the correct conversion of the given price. Choice C ($9.05 /gal) is incorrect as it is too high based on the correct conversion. Choice D ($1.58 /gal) is incorrect as it does not accurately reflect the conversion from pounds to dollars and liters to gallons.

Correct Answer: A

Rationale: The correct order is A: nano- < milli- < centi- < kilo-. The rationale is as follows: 1. Start from the smallest prefix, which is nano- representing 10^-9. 2. Moving up, milli- comes next representing 10^-3, which is larger than nano-. 3. Following milli- is centi- representing 10^-2, larger than milli-. 4. Lastly, kilo- is the largest prefix representing 10^3, making it the largest of the four options. Therefore, the correct order is nano- < milli- < centi- < kilo-. The other choices are incorrect because they do not follow the correct increasing order of magnitude for the metric prefixes.

Correct Answer: A

Rationale: To convert 0494 to L, we first convert it to inches: 494 cm ÷ 54 cm/in = 9.148 in. Then, we convert inches to L: 9.148 in × 1 L/54 in = 0.169 L. The correct answer is A: 1.40 101 L, which is the correct conversion of 0.169 L to scientific notation. Choices B, C, and D are incorrect due to incorrect conversions or not being in scientific notation.

Correct Answer: B

Rationale: The correct answer is B: Alpha particles greatly deflected by the metal foil. In the Thomson model, the atom was thought to be a uniform, positively charged sphere. If this model had been correct, alpha particles would have passed through the foil with little or no deflection. However, Rutherford observed significant deflections, indicating a concentrated positive charge at the center (nucleus). This aligns with the concept of the Rutherford model of the atom. Choices A, C, and D are incorrect because they do not correspond to the experimental observations made by Rutherford.

Correct Answer: D

Rationale: The correct answer is D because when alpha particles are beamed at a thin metal foil, some pass directly through due to their small size and high energy (option A), while others are reflected by direct contact with nuclei in the metal foil (option C). This is based on the Rutherford scattering experiment which showed that alpha particles can be deflected by the positive nuclei in the metal foil. Option B is incorrect as alpha particles are not diverted by attraction to electrons in the foil. Option D combines the correct explanations for the behavior of alpha particles when beamed at thin metal foil.

Correct Answer: C

Rationale: The correct answer is C: Mg2+. A species with 12 protons must have an atomic number of 12, which corresponds to magnesium (Mg). The 10 electrons indicate that it has a 2+ charge, making it Mg2+. Choice A (Ne2+) is incorrect because neon (Ne) has an atomic number of 10, not 12. Choice B (Ti2+) is incorrect because titanium (Ti) has an atomic number of 22, not 12. Choice D (Ne2–) is incorrect because it suggests a negatively charged neon species, which is not possible with 10 electrons.

Correct Answer: A

Rationale: The correct answer is A because it involves a measurable quantity (length) that can be expressed numerically. This is a quantitative observation as it can be described with numbers. Choices B and C describe qualities (color and appearance) which are qualitative observations. Choice D provides a quantitative measurement (temperature) but it is not an observation, rather a measurement.