The angular momentum quantum number of an electron (l) designates the:
a) electron's main energy level
b) shape of the electron's orbital (cloud)
c) order of placement of electrons in the sublevel
d) electron's direction of spin

B

Explanation:

The orbital quantum number shows the direction of the electron cloud. Various values of l reflect various shapes of orbitals. s corresponds to a spherically symmetrical distribution of electrons. p refers to dumbbell distribution of electrons and so on.

a

explanation:

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.