Net charge of histidine in pH 1 3 5 11?

pK1 = 2.3, pKr = 6, pK2 = 9.7 (all approximate)

at physiological pH, histidine has no net charge.

at pH 1, below all pKas and charge is +2

at pH 3, amine group proton pops off, so +1 charge

at pH 5, still below 6 and above 2.3 so +1 charge

if had pH above 6, for instance... at pH of 8 net charge is zero, or neutral... such that it is neutral at physiological pH (a bit above a pH of 7)

at pH 11, exceeds all pKas of amine, acid group, and R group. So net charge of -1

amine deprotonation, carboxylic acid deprotonation, and R group deprotonation happen pH 11 because it exceeds all pKs