Half-life is defined as the time required for half of the atoms of a radioactive substance to break down into other elements. It is a specific measure used to understand the rate of decay of radioactive materials. The other points you've mentioned refer to concepts like radiometric dating and isotopes, which are not the definition of half-life itself.
What is half-life?(3 points) Responses The time required for half of the atoms of a radioactive substance to break down into other elements. The time required for half of the atoms of a radioactive substance to break down into other elements. The geologic age of a fossil, or a geologic event or structure expressed in units of time, usually years. Also known as actual age. The geologic age of a fossil, or a geologic event or structure expressed in units of time, usually years. Also known as actual age. Two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei.
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