How many electrons will be transferred from Mg to SO4 to form MgSO4?

Question

I don't understand how this ionic bond forms?  if you could draw a picture that would help greatly!

Answer 1

Nat,

The sulfate ion has a net charge of -2, meaning it is deficient in 2 electrons in order to have all 5 atoms have a full octet. Each atom contributes only the valence electrons it has. Since Sulfur has 6, and each Oxygen has 6, there are 5 atoms with 6 electrons. This is a total of 30 electrons. When you draw the Lewis Structure of the sulfate ion, you will see that sulfur has a full octet (eight electrons) around it by the four shared bonds with the four oxygen atoms. So, Sulfur would be in the middle like this:

                                                  

                                                                         O

                                                                          |

                                                                O ---- S----O

                                                                          |

                                                                         O

and each dashed line is a shared pair, so it's worth 2 total electrons. That's 8 of the 30. That leaves 22. 

If we put 6 around 3 of the oxygens, we'd have 18 more for a total of 26. That means the final O would have four electrons around it for a total of 30 electrons. This means that this particular O has the four free electrons plus the 2 in the bond for a total of 6. But since it want's eight, it will try to find 2 more and that is why it will steal 2 from another source like Magnesium. Magnesium has 2 valence electrons and thus it would rather give those up than get 6 more because it takes less energy; so when it encounters the sulfate ion, it will donate 2 to the oxygen with only four leaving it +2 and the sulfate ion -2. They will then form the ionic compound MgSO4.  The program won't let me put drawings in, but I hope that helps. 

 

 

                                   

              

Answer 2

Hey Nat -- you're likely wondering about the SO4 part ... the Mg: +2 is easier to see ... both S and O have 3 outer shell e-pairs

 

:S:  :O:  you can get S and 3[O]'s to share, but need another e-pair for [SO4] -2

 ..     ..

 

Mg: +2 provides that 4th e-pair ... Best wishes, sir :)

Answer 3

Nat,

Magnesium has the atomic number 12. There are 12 electrons in the outermost shell. Mg atom would look like  this Mg: (if we ignore the full shells). This molecule is very reactive, as it wants to reach a full shell, and it can do that by losing those two electrons.

When magnesium is reacted with sulfuric acid H₂SO₄, it gives these electrons to the two H⁺ ions, forming H₂ gas, converting Mg: to Mg²⁺. This reaction proceeds because Mg: is more reactive than H₂ towards giving electrons (acting as a reducing agent). H₂ is content as it has full shells for its shared two electrons, and Mg is happier (more stable) as the +2 charge than as Mg:. 

  An illustration of the molecule sulfuric acid is as below. The oxygen atoms on the S=O bonds have two electron lone pairs, while the oxygen atoms in the S-O^-  bonds have three lone pairs. Two hydrogen atoms have donated their electrons to oxygen. Hydrogen has a +1 charge, while oxygen has a -1 charge. The molecule is ionic because here is no sharing of electrons like in the sulfur - oxygen bonds. If you are studying the octet rule, sulfur is one of the exceptions to the rule because of d-orbitals.  

   Hope this helped.