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!

This is because the amount of energy required for an object to move depends on the mass of the object as well. In this case, mass of an alpha particle is much greater than the mass of a beta particle. An alpha particle consists of 2 neutrons and 2 protons whereas a beta particle is just an electron. Hence, alpha particle is approximately 7000 times as heavy as a beta particle, demonstrating why it requires greater energy.