Lithium and the diagonal relationship with magnesium
Lithium is different from the other alkali metals in that it is smaller, and has the highest ionization energy. Its size is closer to magnesium, and the resemblance lithium has with magnesium is called the diagonal relationship. Some similar characteristics between the two are as follows:
- Both lithium and magnesium are harder and have higher melting points than the other metals in their groups.
- Their periodic properties, including electronegativity, atomic radii, ionic radii, and atomic volume are similar.
- Fluorides and phosphates of Li and Mg are hardly soluble in water while those of other alkali metals are soluble.
- They only produce monoxides when reacted with oxygen.
- They combine with carbon when heated with it
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