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 \t element with the larger atomic radius
mn \t ○
cr \t ○
sc \t ○
ti \t ○
y \t ○
nb \t ○
la \t ○
hf \t ○

Explanation:

Step1: Recall atomic radius trends

Atomic radius generally decreases across a period (left to right) and increases down a group (top to bottom) in the periodic table.

Step2: Analyze Mn vs Cr

Mn (Manganese) and Cr (Chromium) are in the same period (period 4) and adjacent to each other. Moving left to right across a period, atomic radius decreases. Cr is to the left of Mn? Wait, no: Cr has atomic number 24, Mn has 25. So Cr is left of Mn in period 4. So Cr has larger atomic radius than Mn.

Step3: Analyze Sc vs Ti

Sc (Scandium, atomic number 21) and Ti (Titanium, 22) are in period 4, Sc is left of Ti. So Sc has larger atomic radius.

Step4: Analyze Y vs Nb

Y (Yttrium, atomic number 39) is in period 5, group 3. Nb (Niobium, 41) is in period 5, group 5. Moving left to right in period 5, atomic radius decreases. Y is left of Nb, so Y has larger atomic radius.

Step5: Analyze La vs Hf

La (Lanthanum, 57) is in period 6, group 3. Hf (Hafnium, 72) is in period 6, group 4. La is left of Hf in period 6, so La has larger atomic radius.

Answer:

• For Mn vs Cr: Cr (select the circle next to Cr)
• For Sc vs Ti: Sc (select the circle next to Sc)
• For Y vs Nb: Y (select the circle next to Y)
• For La vs Hf: La (select the circle next to La)