When elements in the same group form molecules, the number of outer-shell electrons involved is the same and so the number of bonds forming the molecule is the same roo.

Question

Eg. Every element in group 2 (groupII) is a solid metal. When these elements bond with a non-metal, each forms an ion carrying a charge of +2. For this reason, they all form similar compounds with chlorine. Eg. MgCl2, CaCl2

Likewise, the elements of group 17 (group VII) form same number of bonds and therefore form similar molecules eg. HF, HCl

I dont understand the theory or the example please help me understand clearly

Answer 1

each element in group (column) 2, Be, Mg, Cs, Sr etc has just two electrons in its outermost shell. A full shell has more, like 8, and they are held tightly. If there are only two electrons in a shell that holds 8 when full, they are easily lured away by for example a Cl atom that is missing one electron to fill its outer shell. Each of two Cl atoms grabs one electron from the Mg for example and since the electrons are negative the two Cl atoms become -1 charge and the Mg becomes +2 because it now has two more + protons than - electrons. Since the Mg++ and the two Cl - are now of opposite charge and unlike charges attract, they are drawn to each other.

Answer 2

Thanks

Answer 3

You are welcome.