Polonium-210 ($Po$) is a radioactive isotope used in industrial static eliminators. A nucleus of polonium-210 contains 84 protons and 126 neutrons. It decays by emitting an $\alpha$-particle to form a nucleus of an isotope of lead ($Pb$).

Write down the nuclide equation for the decay of polonium to lead.

Static eliminators contain a polonium source that ionizes the air between the device and a highly charged moving surface, allowing the static charge to safely dissipate.

Suggest and explain the effect that a build-up of dust on the polonium source would have on the rate of static discharge.

Suggest two reasons for using an $\alpha$-particle emitter in a static eliminator rather than a beta ($\beta$) or gamma ($\gamma$) source.