What type of radiation has the least penetrating power?

In the same way, which particle is most penetrating?

Alpha particle

In the same way, which radiation type has the greatest penetration ability? Gamma Radiation (x-rays) and high-energy electromagnetic radiation are also known as high-energy photons. This class of radiation has the highest penetrating power. The high energy gamma radiations can pass through several centimeters worth of lead and still be visible on the opposite side.

Another question is: What type of radiation has the lowest penetration ability?

Because it emits the largest and slowest amount of I+-particle, its penetration power is low. You can block it with a piece of paper or your hand. Although beta particles penetrate more than alpha particles they can be stopped with a thin aluminum sheet.

What type of radioactive material has no charge?

Gamma