As the period number increases on the periodic table (moving from the top of the table to the bottom), a. the atomic number increases and the atomic mass decreases. b. the atomic number decreases and the atomic mass increases. c. the number of the principal energy level containing the outer electrons increases. d. the number of the principal energy level containing the outer electrons decreases.

Agas mixture with a total pressure of 745 mmhg contains each of the following gases at the indicated partial pressures: co2, 245 mmhg ; ar, 119 mmhg ; and o2, 163 mmhg . the mixture also contains helium gas. part a what is the partial pressure of the helium gas? phe p h e = nothing mmhg request answer part b what mass of helium gas is present in a 10.2-l sample of this mixture at 283 k ? m m = nothing g request answer

What are the major types of a chemical compound

Energy defines the different "states" of matter. in no more than 3 sentences, describe the amount of kinetic energy that each of the 3 states of matter possesses and relate that to the atom/molecular motion of each "state".