Question

As the period number increases on the periodic table (moving from the top of the table to the bottom),
A.
the number of the principal energy level containing the valence electrons decreases.
B.
the atomic number increases and the atomic mass decreases.
C.
the atomic number decreases and the atomic mass increases.
D.
the number of the principal energy level containing the valence electrons increases.

Answer 1

You should see right away that B and C make no sense,

Atomic mass = Number of Protons + Number of Neutrons

So that leaves

A and D

http://image.tutorvista.com/content/feed/tvcs/PERIODIC_TRENDS2.jpg

Answer 2

The principal energy level is the number of orbitals an atom has.

As you increase the amount of protons you increase the amount of electrons to acquire a neutral charge.

An electron has a charge of -1
A proton has a charge of +1

Answer 3

Note the atomic number is simply the number of protons in an atom

Answer 4

as you move across the table the number of protons increases as the number of protons dictates an elements identity

Answer 5

Ignore that first image i posted half asleep,


See this:

https://en.wikipedia.org/wiki/Electron_shell

Answer 6

hope this helps