How to find molarity from mole fraction and density?

Which is true of transition metals when moving from left to right on the periodic table? the d sublevels are not filled across the period. the cation radii become larger across the period. atomic radii increase slightly and then start to decrease. atomic radii decrease slightly and then start to increase. o

Iknow #2 is d. i just need to know why

Which of the following statements is true about planck’s law