What is the definition of the half-life of a radioactive element?
-> The unstable atoms of the same species (same chemical element) and of differe...
What is the definition of the half-life of a radioactive element?
-> The unstable atoms of the same species (same chemical element) and of different masses, called radioisotopes, do not perform all changes (emissions) at the same time. -> The radiation emissions are made in an unforeseen way, and it is not possible to guess the moment when a certain nucleus will emit radiation. -> However, for a large number of atoms, the number of transformations per second is proportional to the number of atoms that are about to transform at that instant. -> The probability of decay per atom per second must be constant, regardless of how long it has existed. -> The decay constant λ is the probability of decay per atom per second and is a characteristic of each element. -> The activity of the sample can be obtained by the expression: A = λN, where N is the number of atoms in the sample. -> The activity of the sample at the initial instant (t = 0 s) is A(ti) = A0. -> The half-life (T1/2) is the time required for the activity of the sample to decrease by a value that is half the initial activity. -> The half-life can be calculated by the expression: T1/2 = ln(2)/λ. -> The half-life is a characteristic of each radioactive element. a) The time required for the activity of the sample to decrease by a value that is half the initial activity. b) The time required for the activity of the sample to decrease by a value that is one-third the initial activity. c) The time required for the activity of the sample to decrease by a value that is one-fourth the initial activity.
A definição de meia-vida de um elemento radioativo é: a) O tempo necessário para a atividade da amostra diminuir para um valor que é a metade da atividade inicial.
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