BERYLLIUM

Atomic Number: 4
Mass Number: 9.012182
Electron Configuration: 1s²2s²
Crystal Structure: Hexagonal Close-Packed
Density: 1.85 g/cm³
Melting Point: 1278 ^oC
First Ionization Energy: 899 kJ/mol
Second Ionization Energy: 1757 kJ/mol
Atomic Radius: 111 pm
Ionic Radius: 35 pm