Need help checking my chemistry homework

A)Calculate the molarity of a solution made by dissolving 12.5 g of Na2CrO4 in enough water to form exactly 550mL of solution.

B) How many moles of KBr are present in 150mL of a 0.275 M solution


C) Write condensed electron configurations for the following atoms and indicate the number of valence electrons
1. Br
2. Cs
3. Cr
4. Cu+2

D)what is wrong with the following electron configurations for atoms in their ground states? (rewrite correctly)
1. 1s22s23s1
2. [Ne] 2s22p3

A)... (12.5g Na2CrO4 / 550mL) x (1 mole Na2CrO4 / __g Na2CrO4) x (1000mL / 1L) = __ M
plug in molar mass Na2CrO4 and calculate

B).. 150mL x (1L / 1000mL) x (0.275 moles KBr / L) = __ moles KBr

C) & D)..
go to this periodic table..
http://www.ptable.com
click orbitals tab
and get to mousing around