d and f BLOCK ELEMENTS

According to Table 3.3, how accurate was Mendeleev's prediction for the atomic weight of Eka-silicon?

• Inaccurate, predicting 70.
• Very accurate, predicting 72 compared to the found value of 72.6.
• He did not predict its atomic weight.
• He predicted 75, which was far off.

What made Mendeleev's predictions for undiscovered elements particularly bold?

• They were based on dreams.
• They were qualitative descriptions.
• They contradicted all known science.
• They were specific, quantitative forecasts that were later proven remarkably accurate.

What specific action demonstrated Mendeleev's confidence in his periodic law?

• He arranged all known elements perfectly.
• He corrected all atomic weights.
• He memorized the entire table.
• He left gaps in his table and predicted the properties of elements to fill them.

What was unique about Mendeleev's use of the Sanskrit prefix "Eka-"?

• It meant "new" in Sanskrit.
• It was a random name he chose.
• It signified the first undiscovered element below a known element in the same group.
• It was the name of a Russian scientist.

Why did Mendeleev suspect that the atomic weights of some elements might be incorrect?

• He had a new method for measuring atomic weights.
• All atomic weights were known to be incorrect.
• Elements placed according to his scheme based on properties sometimes contradicted the order of atomic weights.
• He believed atomic weights were irrelevant.