Final answer:
The arrangement of elements according to atomic radius is Po > Te > Se > S, following the trends that atomic radii increase when moving down a group and decrease when moving across a period.
Step-by-step explanation:
To determine the arrangement of elements according to atomic radius, we should consider their positions in the periodic table. For the elements Se (selenium), S (sulfur), Te (tellurium), and Po (polonium), we must remember two key trends:
- Atomic radii increase as we move down a group (column) in the periodic table because each successive element has an extra energy level of electrons, making the atom larger.
- Atomic radii decrease as we move across a period (row) from left to right due to the increasing nuclear charge with more protons, pulling electrons closer to the nucleus and making the atom smaller.
Now, considering that S and Se are in the same group with S above Se, and Te and Po are also in the same group with Te above Po, we apply the trends:
- Polonium (Po) is larger than Tellurium (Te) because Po is below Te in the same group.
- Tellurium (Te) is larger than Selenium (Se) since Te is below Se in the same group.
- Selenium (Se) is larger than Sulfur (S) because Se is below S in the same group.
Therefore, the correct order of increasing atomic radius for these elements is:
S < Se < Te < Po
And thus, the answer to the student's question is option (a) Po > Te > Se > S.