Number of unpaired electrons in boron in ground state is/are:

Explanation

Boron has atomic number 5, so its configuration is 1s2 2s2 2p1 and the single 2p electron is the only unpaired one. The 1s and 2s electrons are paired within their orbitals. Boron's three valence electrons allow three bonds, but only one of them is unpaired in the ground state, which is the distinction being tested.