Why should it take significantly more energy to move a beam of alpha particles than a beam of beta minus particles

Beta particles are electrons.

Each alpha particle is a bundle of two protons and two neutrons.
Each proton and each neutron has the same mass as roughly
1,840 electrons. 

So one alpha particle has the mass of almost 7,400 beta particles.
No wonder it takes more energy to influence its motion !

The charge of an ion with 55 protons and 52 electrons is +3. the reason is because protons are positive, and there are three more than the amount of negative electrons.