19. gas a is composed of diatomic molecules (two atoms to a molecule) of a pure element. gas b is composed of monoatomic molecules (one atom to a molecule) of another pure element. gas a has three times the mass of an equal volume of gas b at the same temperature and pressure. how do the atomic masses of elements a and b compare?

The atomic mass of element A is 1.5 times greater than the atomic mass of element B.

Gas A = A2 ( g )

Gas B = B ( g )

3 / 2 = 1.5   ( Lets say Gas A has a mass of 3 units, Gas B then has a mass of 1 unit. There are 2 atoms per molecule in Gas A so we divide the mass between the two. )

1 / 1 = 1   ( Since Gas B has a mass of 1 unit and there is 1 atom per molecule, the unit of mass is attributed only to the 1 atom. )

Element A = 1.5 units

Element B = 1 units

An  atom  (ours, not carroll's) consists of a positively charged  nucleus, surrounded by one or more negatively charged particles called  electrons. the positive charges equal the negative charges, so the atom has no overall charge; it is electrically neutral. most of an atom's mass is in its nucleus; the mass of an electron is only 1/1836 the mass of the lightest nucleus, that of hydrogen. although the nucleus is heavy, it is quite small compared with the overall size of an atom. the radius of a typical atom is around 0.1 to 0.25 nanometres (nm), whereas the radius of a nucleus is about 10-6  nm.  *  if an atom were enlarged to the size of the earth, its nucleus would be only 200 feet in diameter and could easily rest inside a small football stadium.read more on -