Examine the equation. 23490Th→23088Ra+42He What kind of barrier would you need to block the radioactive particles from this reaction?

A. a piece of paper

B. a sheet of aluminum foil

C. a two-inch block of lead

D. a solid concrete block

A. A piece of paper

Explanation:

The equation describes an alpha-decay, in which an alpha particle is produced.

An alpha particle is a nucleus of helium, consisting of 2 protons and 2 neutrons (in the formula, it corresponds to 42He, where 4 is the mass number and 2 is the atomic number).

Among all types of radiation, alpha-radiation is the less penetrating one. In fact, since the alpha particle has a great mass and charge, it easily ionises the atoms of the mediums where it is passing through, releasing its energy at a very fast rate. For this reason, alpha particles usually lose all their energy in a very few mm of material, therefore they can be easily stopped even by a piece of paper.

Answer;

A. a piece of paper

Explanation; The above equation shows an alpha radiation. The radioactive Thorium emits alpha particle to form Radium atom. Alpha particles can be stopped by a sheet of paper, beta particles by aluminum foil, and gamma radiation by a block of lead. Beta particles pass through sheets of paper but are stopped by aluminum foil. Gamma rays are the most difficult to stop due to their high penetrating power and require concrete, lead, or other heavy shielding to block them.