Answer:
Across a row, atomic radii decreases.
Explanation:
It decreases because nuclear charge increases across a row, electrons are added to the same shell and shielding remains constant. Therefore the outer electrons are more attracted to the nucleus making the atom smaller.
The sample with the lowest AVERAGE kinetic energy is
the coolest one.
The sample with the lowest TOTAL kinetic energy depends on
not only the temperature of the samples, but also on their size,
since each molecule in the sample has kinetic energy.