As you might expect, they should be close to "Be"Be in the Periodic Table.
"Mg"Mg is the metal directly below "Be"Be and "Al"Al is diagonally below and to the right of "Be"Be.
Several elements in Period 2 have properties like elements diagonally below them and to the right in Period 3. This is called a diagonal relationship.
Here are some comparisons.
bbul("Property"color(white)(mmm)"Beryllium"color(white)(mm)"Magnesium"color(white)(m)"Aluminium")
"Appearance"color(white)(mmll)"shiny"color(white)(mmmmm)"shiny"color(white)(mmmmm)"shiny"
"Colour"color(white)(mmmmm)"silvery"color(white)(mmmmll)"silvery"color(white)(mmmml)"silvery"
"Hardness"color(white)(mmmll)"fairly soft"color(white)(mmml)"fairly soft"color(white)(mmm)"fairly soft"
"Rxn with H"_2"O"color(white)(m)"H"_2 + "Be(OH)"_2color(white)(ll)"H"_2 + "Mg(OH)"_2
"Rxn with O"_2color(white)(mm)"BeO"color(white)(mmmmmll)"MgO"color(white)(mmmmml)"Al"_2"O"_3
"Rxn with acids"color(white)(m)"slow because of protective oxide film on surface"
"Rxn with NaOH" color(white)(l)"Be(OH)"_4^"2-"color(white)(mmmmmmmmmmm)"Al(OH)"_4^"-"
I_1"/kJ·mol"^"-1"color(white)(mmm)900color(white)(mmmmmm)738color(white)(mmmmmm)578
EA"/kJ·mol"^"-1" color(white)(mmml)0 color(white)(mmmmmmm)0color(white)(mmmmmmll)42
