Question 1

Which of the following best explains why the atomic radius of transition metals changes only slightly across a period compared to main group elements?

Accepted Answer

The number of outermost electrons remains constant across the period for transition metals.

Question 2

What is the primary cause of the lanthanide contraction observed in period 6 transition metals?

Accepted Answer

An increase in effective nuclear charge $$ (Z_{\mathrm{eff}}) $$ due to the filling of the 4f subshell.

Question 3

Which element would you expect to have the largest atomic radius: Ni or Ti?

Accepted Answer

Ti

Question 4

Why do period 5 and period 6 transition metals have similar atomic radii, despite period 6 elements having more electrons?

Accepted Answer

Lanthanide contraction increases $$ Z_{\mathrm{eff}} $$, pulling electrons closer and reducing atomic size.

Question 5

Which of the following transition metals would you expect to be larger, but is actually the same or nearly the same size as Tc (technetium)?

Accepted Answer

Re

Question 6

Across a period, the number of outermost electrons in transition metals is:

Accepted Answer

Constant

Question 7

Which of the following best describes the trend in atomic radius for main group elements as you move from left to right across a period?

Accepted Answer

Atomic radius decreases

Question 8

A chemist is comparing the atomic radii of Zr and Nb. Which element is expected to have the larger atomic radius and why?

Accepted Answer

Zr, because it is to the left of Nb in the same period.

Question 9

Which of the following statements about effective nuclear charge $$ (Z_{\mathrm{eff}})  is $$correct in the context of transition metals?

Accepted Answer

$$ Z_{\mathrm{eff}} $$ increases across a period, causing a slight decrease in atomic radius.

Question 10

A student claims that the atomic radius of Ru (ruthenium) should be much larger than that of Tc (technetium) because it is in the next period. Is this correct? Why or why not?

Accepted Answer

No, because lanthanide contraction causes Ru and Tc to have similar atomic radii.

Question 11

Which of the following best describes the effect of adding electrons to the same shell in transition metals?

Accepted Answer

It increases electron-electron repulsion, but the increase in $$ Z_{\mathrm{eff}} $$ dominates, causing a slight decrease in atomic radius.

Question 12

Which of the following pairs of elements would you expect to have the most similar atomic radii due to the lanthanide contraction?

Accepted Answer

Mo and W

Question 13

If the atomic radius of Zr is 160 pm and that of Hf is 159 pm, what phenomenon explains the small difference despite Hf being in a lower period?

Accepted Answer

Lanthanide contraction

Question 14

Which of the following is a direct consequence of the lanthanide contraction for transition metals in period 6?

Accepted Answer

Period 6 transition metals have smaller than expected atomic radii.

Question 15

Which of the following statements is true regarding the trend in atomic radius down a group for transition metals?

Accepted Answer

The increase in atomic radius is less than expected due to lanthanide contraction.

Question 16

A medical researcher is studying the use of platinum (Pt) compounds in chemotherapy. Based on periodic trends, which element would you expect to have a similar atomic radius to Pt?

Accepted Answer

Ir

Atomic Radius and Density of Transition Metals: Trends and Lanthanide Contraction

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