The sulphate ion has a charge of 2-, and potassium has a charge of 1+. To fully neutralise the charge on a sulphate ion, you need two potassium ions.
However, strontium has a charge of 2+. To neutralise the sulphate ion's 2- charge, one strontium ion is enough, so only one bonds to the sulphate.
Hope I helped! xx
If you follow the octet rule, you know that an element must have 8 outside (or valence) electrons to be energetically favorable.
In CCl4, the carbon molecule forms four bonds; one for each chlorine atom. Each bond contains 2 electrons, so it is satisfied.
In PCl3, Phosphorous forms only 3 bonds with chlorine, which means in order to have 8 valence electrons, it also has a lone pair of electrons, not bonded with chlorine.
Now, in CCl4, picture the shape of the molecule like a plus sign, with the carbon in the middle and the chlorine at the four ends. It is symmetrical, and therefore is nonpolar.
In PCl3, the lone pair electrons <em>push</em>, so to speak, the 3 chlorine atoms away, making a T-shaped molecule. Since the chlorine is more electronegative than carbon, the molecule is unbalenced, making it polar.
There will be a maximum of 2 electrons that can <span>occupy a single molecular orbital. They will have opposite spins. Hope this answers the question. Have a nice day. Feel free to ask more questions. Have a nice day.</span>
