Draw the Lewis electron dot diagram for ion Mg2+;
The correct answer and explanation is:
Lewis Electron Dot Diagram for Mg²⁺:
The Lewis dot diagram for the Mg²⁺ ion is:
[Mg]²⁺
✔ There are no dots around the element symbol because magnesium has lost its two valence electrons.
300-Word Explanation:
The Lewis electron dot diagram is a representation of the valence electrons of an atom or ion using dots around the element’s symbol. Valence electrons are the outermost electrons of an atom and are responsible for chemical bonding.
Magnesium (Mg) is in Group 2 of the periodic table, which means it has two valence electrons in its neutral state. The electron configuration of neutral magnesium is:
- Mg (atomic number 12): 1s² 2s² 2p⁶ 3s²
The two electrons in the 3s orbital are the valence electrons.
When magnesium forms an ion (Mg²⁺), it loses both of its valence electrons to achieve a more stable electron configuration—similar to that of a noble gas (neon, in this case). The resulting electron configuration of Mg²⁺ is:
- 1s² 2s² 2p⁶
This configuration represents a full octet, which is energetically favorable.
Because Mg²⁺ has lost its two valence electrons, there are no dots in the Lewis diagram. Instead, we simply write [Mg]²⁺ to indicate the magnesium ion and its +2 charge. The absence of dots shows the loss of valence electrons.
This is different from a neutral atom’s Lewis diagram, where dots represent the number of valence electrons. For example, a neutral Mg atom would be shown as:
- Mg: with two dots: one on each side to represent the two valence electrons.
In summary, Mg²⁺ does not have any valence electrons, so the correct Lewis dot diagram is just the element symbol in brackets with a 2+ charge:
→ [Mg]²⁺.