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Adding these two values gives the original amount of parent isotopes in the sample.
The Earth orbits the Sun in about one year's time, the Earth rotates on its axis every 24 hours, 60 ticks of the second hand on a clock indicates 1 minute has passed.
The element is listed by its atomic symbol, a one-, two- or three-letter long label. Above the atomic symbol, each entry lists the element's atomic number; e.g., the element gold (Au) has an atomic number of 79.