As you might expect, they should be close to #"Be"# in the Periodic Table.
#"Mg"# is the metal directly below #"Be"# and #"Al"# is diagonally below and to the right of #"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#
