The valence electrons of lithium and beryllium metal are spherically shaped and easily lost. Once lost, the remaining two electrons revert back to being helium-like electrons except that the kernel, being laden with more charge than helium, sucks in the remaining two even closer. This explains the extremely small sizes of both Li+ and Be2+ and ultimately why lithium is such an effective battery material and why even tinier beryllium is found in many brilliant gemstones.
Things change dramatically when we move on to boron, a favorite element of mine. The electrons actually reach out further and take shapes.