The presence or absence of electrical charges in individual atom can be detected. Charged atoms are known as ions. Ions can also represent the states of trinary logic. The contents of an ionic SEM chip could be changed by means of precisely directed electrical currents. Another way in which SEM might operate involves the relative energy states of atoms depending on the positions, or orbits, of electrons within.
Every atom has several different energy levels, called shells, at which electrons can exist.
The shells resemble spheres surrounding the nucleus. The larger the diameter of the shell, the greater the energy contained in an electron orbiting in that shell. The contents of such a memory could be changed using tiny electromagnetic pulses directed at specific atoms in a chip.