Practice!

Sample Problem

Abridged Periodic Table

B

C

1

2

F

3

Si

P

S

4

Use the abridged periodic table above to answer the following question

Which correctly lists atoms in order of increasing atomic radius?

Solution

Recall that electron shells and electron shielding (contraction) determine atomic size. Though element 4 has more valence electrons than elements 1 and 2 (by 2 and 1 respectively), its decrease from contraction is less than the increase from having another electron shell. Therefore, the order of increasing radius is 2, 1, 4, 3.