Lithium is an alkali metals whereas magnesium is an alkaline earth metal. Lithium is present in 1st group and magnesium is in 2nd group. The chemical properties of Li and Mg are similar due to diagonal relationship.


1.) The size of Li and Mg are similar.
2.) Li and Mg are harder and hence have high melting point irrespective of their group elements.
3.) Both show covalent nature.
4.) Carbonates of Li and Mg decomposes on heating to liberate CO2.
5.) Li and Mg can directly combine with N2.
6.) Both Li and Mg combine with carbon on heating.
7.) Both of these do not form alums.

Charge/Size Ratio:
- Lithium and magnesium belong to the same group in the periodic table, Group 2.
- Both elements have similar charge/size ratios due to their position in the periodic table.
- Lithium has a charge of +1 and a relatively small size, while magnesium has a charge of +2 and a slightly larger size.
- The charge/size ratio affects the chemical behavior of the elements, leading to similar properties.

Explanation:
- The charge/size ratio plays a significant role in determining the chemical properties of elements.
- Elements with similar charge/size ratios tend to exhibit similar chemical behavior.
- In the case of lithium and magnesium, their charge/size ratios are comparable, leading to similarities in their properties.
- This similarity is evident in their reactivity, ionization energy, and formation of compounds.

Reactivity:
- Both lithium and magnesium are reactive metals due to their tendency to lose electrons.
- They readily form ionic compounds with non-metals, such as oxygen, to achieve a stable electronic configuration.
- The reactivity of these elements is a result of their charge/size ratio, which influences the ease of electron loss.

Ionization Energy:
- The ionization energy of lithium and magnesium is relatively low compared to other elements.
- This is because of their charge/size ratio, which makes it easier for them to lose electrons and form positive ions.
- The ionization energy of an element is influenced by its charge/size ratio, leading to similarities in lithium and magnesium.
In conclusion, the similar properties of lithium and magnesium can be attributed to their comparable charge/size ratios. This relationship highlights the importance of the position of elements in the periodic table in determining their chemical behavior.