The positively charged particle consisting of 2 protons and 2 neutrons given off by a radioactive substance is called an alpha particle.

Here's why:

* Alpha particles are essentially the nucleus of a helium atom (He-4).

* They have a +2 charge due to the two protons.

* They are relatively large and heavy compared to other types of radiation.

* Alpha particles are emitted during a type of radioactive decay known as alpha decay.