If an isotope of some element has a half-life of 300 years, about how much of the isotope atoms will be in a sample after 300 years?

The isotope atom in the sample after 300 years will be half.

Explanation:

If the half life of the isotope of an element is 300 years, after 300 years, in this case the mass of the sample provided will become half of the previous initial mass of the substance. As we know the half life is the time that is required for the element to change or decay. The radioactive isotopes have their own half life which are found to be independent of various factors i.e. temperature, concentration and other chemical changes.  

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so yes an egg will float in salt

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