Among the elements of the main group, the general trend in the first ionization energy moving across a period is not followed between group 2 and group 13. Which best explains these exceptions?
The ionization energy decreases because the full s orbital shields the electron entering the p orbital.
The ionization energy increases because the full s orbital shields the electron entering the p orbital.
The ionization energy decreases because the stability of the half-full p subshell is increased.
The ionization energy increases because the stability of the half-full p subshell is increased.

Hot air balloons float in the air because of the difference in density between cold and hot air. in this problem, you will estimate the minimum temperature the gas inside the balloon needs to be, for it to take off. to do this, use the following variables and make these assumptions: the combined weight of the pilot basket together with that of the balloon fabric and other equipment is w. the volume of the hot air inside the balloon when it is inflated is v. the absolute temperature of the hot air at the bottom of the balloon is th (where th> tc). the absolute temperature of the cold air outside the balloon is tc and its density is ďc. the balloon is open at the bottom, so that the pressure inside and outside the balloon is the same. as always, treat air as an ideal gas. use g for the magnitude of the acceleration due to gravity.

How many moles of air are there in a human lung with a volume of 2.4 l at stp? explain your answer

Compare and contrast physical changes with chemical changes.