Predict a likely mode of decay for each unstable nuclide. a. Mo-109 b. Ru-90 c. P-27 d. Sn-100

Name: Problem 41, Chapter 20: Chemistry: Structure and Properties
Uploaded: 2019-11-09T22:55:47-08:00
Duration: 3 min 32 s
Channel: Matthew Hurlock
Description: Predict a likely mode of decay for each unstable nuclide. a. Mo-109 b. Ru-90 c. P-27 d. Sn-100

Predict a likely mode of decay for each unstable nuclide. a....

Key Concepts

Proton Emission

Proton emission is a less common decay mode that occurs in extremely proton-rich nuclei. It involves the direct emission of a proton from the nucleus as it attempts to lower its proton-to-neutron ratio. This process is a clear indicator of a nucleus lying outside the proton drip line.

Alpha Decay

Alpha decay is a process where the nucleus emits an alpha particle (two protons and two neutrons), which typically occurs in heavier nuclei to reduce both the atomic number and mass number. This mode of decay is favored when the release of an alpha particle results in a significant gain in nuclear binding energy and a more stable daughter nucleus.

Decay Modes and Energetics

Different decay modes, such as beta decay, positron emission, electron capture, alpha decay, and proton emission, occur when the transformation lowers the total energy of the nucleus. The selection of a particular decay mode is determined by energy considerations (Q-value), angular momentum conservation, and whether the parent nucleus is proton-rich or neutron-rich.

Nuclear Stability

This concept explains that nuclides far from the valley of stability (where binding energy is maximized) tend to be unstable and will undergo radioactive decay in order to achieve a more stable configuration. The imbalance in the number of protons and neutrons often triggers specific decay processes that move the nuclide closer to the line of stability.

Beta Decay (?? and ??) and Electron Capture

Beta decay involves the conversion of a neutron to a proton (?? decay) or a proton to a neutron (?? decay), with the emission of an electron or positron and an accompanying neutrino or antineutrino. In some cases, especially for proton-rich nuclei, electron capture is preferred; it involves the nucleus capturing an orbital electron to convert a proton into a neutron, thereby moving the nuclide toward a more balanced state.

Transcript

00:01 So here we have a list of unstable nuclei, and we're asked to predict the type of decay that each one is going to undergo.

00:08 So as a reference, i've included a screenshot of the graph plotting nuclear stability based on the atomic number and the number of neutrons.

00:18 The green dots in this plot represent stable nuclei.

00:21 The yellow dots represent unstable nuclei.

00:24 And the primary principle that we should be considering when we think about nucleide stability is the ratio between the neutrons and the plot.

00:31 Protons because if our ratio of neutrons over protons is greater than one, what that means is that we have too many neutrons.

00:48 And what will happen, the only thing that we can do, or the quickest things that we can do to change this ratio are not, basically our non -alpha emission decays.

00:56 So we have too many neutrons, we're going to undergo beta decay because in beta decay, in the nucleus we convert a neutron into a proton.

01:06 Conversely, if our neutron to proton ratio is less than one, that means we need more neutrons.

01:20 The two types of changes that we can have there are either electron capture or positron emission.

01:37 So if we look at the elements that we've been given, and we consider their neutron of proton ratios.

01:42 For this, myelodem 109 species, the neutron to proton ratio is greater than one.

01:48 So what that means is that our predicted decay from all of denim is going to be beta decay...

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