in form of an ion calcium has actually lost two of its electrons hence there are 20 – 2 = 18 electrons in an ion of calcium and making its diagram the electronic structure becomes 2, 8, 8….

I suppose you are from a higher education level than GCE O Level Sec 4/5 or US
Grade 9-11 since they do not really learn about Dipole Dipole Attraction.

For GCE O Level standard, i would like to state that dipole-dipole is the ‘same’ as
Ionic Bonding. This is to make sure they are not confused with new chemistry
terms that are not tested.

But in reality and higher education, Dipole-Dipole is only Similar to Ionic Bonding,
this meaning that they are different.

Ionic Bonding occurs when there is one element that loves to give electrons away (i.e. Grp 1 metal) and an element that loves to
take in electrons (i.e. Grp 7 halogens). There is a distinct and specific electron transfer from one element to another.

In dipole-dipole, the two elements do not have High tendency to lose and gain an
electron. Instead, there is slight amount of sharing within the 2 elements.

Detailed explaination can be seen at: http://web.mst.edu/~gbert/INTERACT/intermolecular.HTM

Hope that helps,
Sean