Question

A large atom decays and emits a particle. After the reaction is complete, the atom’s mass has changed substantially. What kind of particle has most likely been emitted?

alpha particle
beta particle
positron
photon

Answer 1

The answer your looking for is, A. alpha particle.

Answer 2

alpha particle

Step-by-step explanation:

In a process where alpha particle is emitted, a heavier nuclei decays into lighter nuclei. The alpha particle released has a charge of +2 units.

`_Z^A\textrm{X}\rightarrow _(Z-2)^(A-4)+_2^4\alpha`

The atomic mass of the resulting lighter nuclei reduces by 4.

The process in which beta particle is emitted, a neutron gets converted into a proton and an electron releasing a beta-particle. The beta particle released carries a charge of -1 units.

`_Z^A\textrm{X}\rightarrow _(Z+1)^A\textrm{Y}+_(-1)^0\beta`

The mass of the resultant nuclei remains same.

The process in which a proton gets converted to neutron and an electron neutrino, a positron is released. This particle carries a charge of +1 units.

`_Z^A\textrm{X}\rightarrow _(Z-1)^A\textrm{Y}+_(+1)^0e`

The mass of the resultant nuclei remains unchanged.

In gamma ray emission,

`_Z^A\textrm{X}^*\rightarrow _Z^A\textrm{X}+_0^0\gamma`

A photon is emitted. An unstable nuclei gets stabilized by release of photon. There is no change in the nuclei.

Thus, in a reaction of decay of a large atom, release of alpha particle would result in substantial change in atomic's mass.