Answer
a). $6.4\times10^{-19}C$
b). 2 electrons
Work Step by Step
a). 1 alpha particle has 2 protons, 2 alpha particles will have 4 protons. The charge on 1 proton = $1.6\times10^{-19}C$
The charge on 4 protons will be = $4\times1.6\times10^{-19}C=6.4\times10^{-19}C$
b). 1 alpha particle has 2 protons.
The atoms are electrically neutral and thus to neutralize the charge of 2 protons, 2 electrons will be needed.
The alpha particle will have to accommodate 2 electrons to become a Helium atom.
