Type of circuit does charge move in only one direction

A diode is a device that allows charges to move in only one direction. A diod consists of a PN-junction, with a semiconductor N-type region (with excess of electrons) bonded with a semiconductor P-type region (excess of holes). The region closed to the junction is called 'depletion zone', where electrons from the n-region recombine with holes from the p-region, and acts as an insulating zone. 

The n-region is then connected to the negative terminal of a battery, and the p-region to the positive terminal. This way, if the applied potential difference is strong enough, electrons will start to flow from the n-region (and then also from the depletion region) to the posititive terminal of the battery, while the holes will flow to the negative terminal, so a net current is flowing through the junction.

Vicceversa, if the two n-region is connected to the positive terminal and the p-region to the negative terminal, nothing happens through the junction, because both electrons and holes of the two regions are attracted by the "wrong side": in the n-region, electrons will flow to the negative terminal (so, not crossing the junction), and in the same way the holes of the p-region will flow to the positive terminal without crossing the junction, so no current is flowing through it.

This is what i found on google “what happens to the bond angle when you add or remove an electron domain? the bond angle decreases as you add domains 5. can you force the atoms into new configurations by pushing atoms around? note: we can think of a bond or a lone pair of electrons as a “domain” of electrons.” i hope this you