When a radioactive isotope releases an alpha particle, the atomic number of the atom is (2 points) decreased by one. increased

When alpha decay takes place, two protons and two neutrons are forcefully ejected from the nucleus in a way that looks very similar to a Helium nucleus. This type of decay causes the atomic mass of the parent particle to drop by four (four particles lost), but the atomic number drops by only two (two protons lost). Therefore, your answer is C.

The best possible answer to this question would be option C

The correct answer is decreased by two.

Explanation:

Alpha particle is emitted when a radioactive isotope undergoes alpha decay process. In this process a heavier particle decays into a lighter particle with the release of alpha particle. The alpha particle carries a mass of 4 units and a charge of +2 units.

The atomic number of the atom gets reduced by 2 units and atomic mass of the same atom gets reduced by 4 units.

The equation representing alpha decay process is:

[tex]_Z^A\textrm{X}\rightarrow _{Z-2}^{A-4}\textrm{Y}+_2^4\alpha[/tex]

Hence, the correct answer is decreased by two.

Thus atomic number of the atom decreases by 2 units.

Explanation: Alpha decay : When a larger nuclei decays into smaller nuclei by releasing alpha particle. In this process, the mass number and atomic number is reduced by 4 and 2 units respectively.

General representation of an element is given as:[tex]_Z^A\textrm{X}[/tex]

where,

Z represents Atomic number

A represents Mass number

X represents the symbol of an element

General representation of alpha decay :

[tex]_Z^A\textrm{X}\rightarrow _{Z-2}^{A-4}Y+_2^4\alpha[/tex]

When a radioactive isotope releases an alpha particle, the atomic number of the atom is decreased by four.

So, the correct answer is B.

Hope this helps,

Davinia.

Correct Option B i.e. decreased by four

Reason: 
Alpha particle are Helium nucleus (4 2 He). Hence, when an alpha particle is emitted from the radioactive particle, for mass balance, it's atomic number decreases by 2, while atomic mass number decreases by 4. For instance, consider following radioactive disintegration process:

                            238 92U   →   234 90Th + 4 2He

From above example, it can be seen that, upon emission of alpha particle, mass number of 'U' decreased by 4. 

I believe it's B. Decreased by four. The mass number of the atom will have an amount of 4 less than the original radioactive isotope mass number, prior to the release of the alpha particle.

The atomic number decreases by 2 and the relative atomic mass decreases by 4, emitting a helium nucleus(having charge of +2) .

The atomic number of the atom will be decreased by two

The radioactive isotope's atomic number decreases by two, and the alpha particle has an atomic number of 2. It wasnt clear which one you were asking for, so there is both.