Question

How are alpha rays produced? Mention any two properties.

Answer 1

An alpha particle is produced by thealpha decay of a radioactive nucleus. ... The piece that is ejected is the alpha particle, which is made up of a two protons and two neutrons: this is the nucleus of the helium atom.

1.     Alpha, α – particle carries double the positive charge of proton, which is equal to the charge on the helium nucleus.

2.      Mass of an alpha, α – particle is roughly four times that of hydrogen atom i.e. it is equal to the mass of the helium nucleus.

The above two properties establish that an alpha, α – particle is equivalent to helium nucleus (or a helium atom which has lost its two orbital electrons i.e. a doubly ionized helium atom).

Answer 2

(i) Certain combinations of neutrons and protons in a nucleus are stable. For example, in a stable bismuth atom there are 83 protons and 126 neutrons. This is called bismuth-209 (126 + 83 = 209). It will always be bismuth-209*. But if we were to add one more neutron to this atom, and make it bismuth-210, it would now be unstable, or radioactive. The atom will eventually spontaneously change or "decay", to become more stable. There are only certain ways it can do this. One way is to emit an alpha particle. In this transition, it spits out a piece of itself (the alpha particle), and becomes more stable. The alpha particle is the radiation given off during the process of "alpha decay".
(ii) Another way to produce alpha particles is to "force" an atom to emit one. This is done by taking advantage of certain properties of various atoms. Here's an example. If we take some regular atoms of boron-10 (five protons, five neutrons), and expose this boron to a field of slow-moving neutrons, some of the boron atoms will absorb a neutron. When this happens, the outcome is not what you'd expect. The boron-10 does not just become stable boron-11. A likely possibility is that the "excited" boron atom will emit an alpha particle, becoming stable lithium in the process. There are other atoms that behave in this fashion.