Butane, ch3ch2ch2ch3, has a higher boiling point than propane, ch3ch2ch3. this is due to:

Explanation:

Boiling point - the temperature at which the the vapor pressure of the liquid equals the external atmospheric pressure.

From the question,

Butane and propane have different number of carbon atoms ,

Now to convert the liquid to gas , energy in the form of heat is provided , now to melt butane more amount of energy is required , due to more number of atoms present in butane , more energy is required and hence , butane has more boiling point .

In comparison to butane , propane has lesser atoms and hence , require less energy to convert liquid propane to gaseous propane , and therefore has less boiling point.

d.) circle motion requires a force to give it a centripetal acceleration.

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.