Question

What is the Lewis Dot structure for $M{g}^{2+}$?

Answer 1

Hint : The Lewis dos structure of an element represents the number of electrons in the valence shell of the atom. Remember that the atomic number of Mg is 12 and a positively charged ion is formed by losing an electron.

Complete Step By Step Answer:
First, let us understand what a Lewis structure is. A Lewis Structure is a simplified representation of a molecule's valence shell electrons. It's used to demonstrate how electrons in a molecule are organized around individual atoms. The Lewis symbol does not indicate electrons that are not in the valence level. The explanation for this is that the number of valence electrons, not the number of inner electrons, determines the chemical reactivity of an element's atom. Lewis structures for compounds or molecules with bonds between atoms are written using a combination of Lewis symbols for atoms. Electrons are shown as "dots" or as a line between two atoms when they are bonded. The aim is to find the "right" electron configuration, which requires that the octet rule and formal charges of the entity (atom/ion/molecule/compound) to be equal.
First we will observe the electronic configuration of an Mg atom which is $1s^{2}2s^{2}2p^{6}3s^2$. This can be found easily by knowing its atomic number. Here, the valence shell is 3 and the number of electrons in there is 2. So, the Lewis structure would have two dots as shown in the diagram below here.

Now the $M{g}^{2+}$ ion is formed when Mg loses two electrons. So, the configuration of the ion is $1s^{2}2s^{2}2p^6$. Observe here that, the valence shell of this ion is 2 and the number of electrons in there is 8. So, the Lewis structure would have eight dots and the net charge should also be mentioned as it is a charged species. Hence, the Lewis structure of $M{g}^{2+}$ is,

Note :
Note that, the Lewis structure makes no attempt to describe molecule geometry, bond formation, or electron sharing between atoms. It is the most basic and restrictive theory of electronic structure.