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Boron cannot donate electrons to other atoms to form an ionic bond featuring a B3+ ion, as the electrons are too tightly bound to the nucleus. Boron generally does not accept electrons to form a negative ion, so it does not normally form ionic compounds — the chemistry of boron is essentially covalent. The electron configuration and consequent bonding behavior also determines the crystalline structure of boron in its various elemental forms.

Boron compounds can often be described as “electron deficient,” in that there are fewer electrons involved in bonding than are required for normal covalent bonds. In a single covalent bond, two electrons are shared between atoms and in most molecules, the elements follow the octet rule. The structures of boron compounds such as boron trifluoride (BF3) and boron trichloride (BCl3), however, show that the element has only six, and not eight, electrons in its valence shell, making them exceptions to the octet rule.