Physical properties of the group 2 elements

Selected physical properties of the group 2 elements are listed

in Table 1.1. The intense radioactivity of Ra makes it impossible to obtain all the data for this element. Some general points to note from Table 1.1 are as follows.

• The general trend in decreasing values of IE₁ and IE₂ down the group is broken by the increase in going from Ba to Ra, attributed to the thermodynamic 6s inert pair effect .
• High values of IE₃ preclude the formation of M³⁺ ions.
• Quoting a value of rion for beryllium assumes that the Be²⁺ion is present in BeF₂ and BeO, a questionable assumption.
• There are no simple explanations for the irregular group variations in properties such as melting points and Δ_aH^o.
• Values of E^o for the M²⁺/M couple are fairly constant (with the exception of Be), and can be explained in a similar way as for the group 1 metals.