Can some please help me understand what this means!! Write the electron configurations of the following elements. Only write them as noble gas or full if it states to do so.

1. Phosphorus (P) Full configuration :

2. Ruthenium (Ru) Full configuration :

3. Barium (Ba) Noble gas configuration :

4. Thorium (Th) Noble gas configuration :

Phosporus- 1s2 2s2 2p6 3s2 2p3

Ruthenium- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d6

Barium- (Xe)6s2

Thorium- (Rn) 6d2 7s2

"you start with 15.67 g mgco3-xh2o, when heated and all the water is removed, you are left with 7.58 g mgco3 only.

therefore, you had 15.67 - 7.58 = 8.09g h2o  

moles of each :

7.58g mgco3 = ? moles = 7.58g / 83.4g/mole = 0.09moles  

8 09g h2o = ? moles = 8.09g / 18g/mole = 0.44moles  

molar ratio between the two by dividing both numbers by the smallest number :

0.09 / 0.09 = 1  

0.44 / 0.09 = 4.8  

mgco3-5h2o"