For 10 points, identify this lightest metalloid with atomic number 5 and symbol B.
The two naturally occurring isotopes of this element possess nuclear spins of 3 and 3/2 and thus may be used for NMR. It is a component of the naturally occurring mineral, ulexite, in which parallel fibers transmit light, creating a fiberoptic effect. In organic chemistry, a compound of this element is used in an addition reaction to an alkene in anti-Markovnikov orientation as opposed to oxymercuration. In forming trigonal planar molecules with the halogens, this element disobeys the octet rule. This is because it possesses only three valence electrons and thus forms only three bonds. For 10 points, identify this lightest metalloid with atomic number 5 and symbol B.
The two naturally occurring isotopes of this element possess nuclear spins of 3 and 3/2 and thus may be used for NMR.
{boron} [accept {B} before mentioned]