Each of the following nuclei undergoes either beta decay or positron emission. Predict the type of emission for each: b. ⁹⁹₃₈Sr

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Identify the type of decay by considering the neutron-to-proton ratio in the nucleus.

Calculate the neutron number: Neutrons = Mass number - Atomic number = 99 - 38.

Determine if the nucleus is neutron-rich or proton-rich: Compare the neutron-to-proton ratio to the stable ratio for elements around strontium.

If the nucleus is neutron-rich, it is likely to undergo beta decay (\(\beta^-\) decay) to convert a neutron into a proton.

If the nucleus is proton-rich, it is likely to undergo positron emission (\(\beta^+\) decay) to convert a proton into a neutron.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Beta Decay

Beta decay is a type of radioactive decay in which a nucleus emits a beta particle, which can be an electron (beta-minus decay) or a positron (beta-plus decay). In beta-minus decay, a neutron is converted into a proton, increasing the atomic number by one, while in beta-plus decay, a proton is converted into a neutron, decreasing the atomic number by one. This process helps unstable nuclei achieve a more stable configuration.

Positron Emission

Positron emission, also known as beta-plus decay, occurs when a proton in the nucleus is transformed into a neutron, releasing a positron (the antimatter counterpart of an electron) and a neutrino. This process decreases the atomic number of the element by one, resulting in the formation of a different element. Positron emission is common in isotopes that are proton-rich and seek stability.

Nuclear Stability and Decay Modes

Nuclear stability is determined by the ratio of protons to neutrons in a nucleus. Isotopes with an imbalance in this ratio may undergo decay to reach a more stable state. The type of decay—whether beta decay or positron emission—depends on whether the nucleus has excess neutrons or protons. Understanding the stability of a nucleus is crucial for predicting its decay mode.