Step-by-step explanation:
Atomic number of boron is 5 and its electronic configuration is
. Boron is a non-metal and belongs to group 13.
That is, 2s shell of boron atom contains 2 electrons and 2p shell of the atom has 1 electron.
Therefore, we can conclude that the value of A equals 2 and value of B equals 1 in B: 1s2 2sA2pB.