Question

in each pair, choose the element with the bigger atoms.
note: solve this problem using only the location of each element in the periodic table.

element pair	element with the larger atomic radius
ti <br> cr	○ <br> ○
tc <br> mo	○ <br> ○
zr <br> y	○ <br> ○

Explanation:

Step1: Recall atomic radius trends

Atomic radius generally increases down a group (more electron shells) and decreases across a period (increased nuclear charge pulls electrons closer).

Step2: Analyze each pair

• Sc vs Mn: Both in period 4. Sc (group 3) is left of Mn (group 7). Across period, radius decreases. So Sc has larger radius.
• Ti vs Cr: Both period 4. Ti (group 4) left of Cr (group 6). Radius decreases across period. Ti is larger.
• Tc vs Mo: Mo is in period 5, Tc in period 5? Wait, Mo (period 5, group 6), Tc (period 5, group 7). Wait, no: Mo is period 5, Tc period 5? Wait, Mo is above Tc? No, Mo (atomic number 42), Tc (43). Wait, down a group: Mo is in group 6, Tc group 7? Wait, no, Mo is period 5, Tc period 5? Wait, no, Mo is in period 5, Tc period 5? Wait, actually, Mo is in period 5, Tc period 5? Wait, no, Mo (atomic number 42) is in period 5, group 6; Tc (43) period 5, group 7. Across period, radius decreases. But wait, Mo is above W, Tc above Re. Wait, no, the pair is Tc and Mo. Wait, Mo is in period 5, Tc period 5? Wait, no, Mo is period 5, Tc period 5? Wait, atomic number: Mo (42), Tc (43). So same period, Mo left of Tc. So Mo has larger radius.
• Zr vs Y: Y (period 5, group 3), Zr (period 5, group 4). Y is left of Zr? Wait, Y is group 3, Zr group 4, same period. Wait, no: Y is period 5, Zr period 5. Y is left of Zr? Wait, atomic number Y (39), Zr (40). So same period, Y is left, so Y has larger radius? Wait, no: atomic radius decreases across period. So Y (group 3) has larger radius than Zr (group 4) in same period.

Step3: Mark the larger ones

• Sc (vs Mn): Sc
• Ti (vs Cr): Ti
• Mo (vs Tc): Mo
• Y (vs Zr): Y

Answer:

For each pair, mark:

• Sc (over Mn)
• Ti (over Cr)
• Mo (over Tc)
• Y (over Zr)

(In the table, mark the circle for Sc, Ti, Mo, Y respectively in their rows.)