Dating method 1 The initial number of parent nuclides may be guessed

1 Dating method 1 The initial number of parent nuclides may be guessed 

The simplest method is based on Equation 5-2, in which the initial number of parent atoms is assumed to be known. Therefore, the calculation of the age is simple  

This method is used mainly for short-lived radioactive nuclides produced by cosmic ray spallation, such as °Be, A1, Si, C1, and Ar (Table 5-1). Because these nuclides have relatively short half-lives, if there was any initial amount of the nuclides at the beginning of Earth history, the initial amount would have completely decayed away. The small amount that can be found in 

Nuclide of Protons of Neutrons Daughter Half-life (yr) Decay Constant (yr ) 

In the atmosphere, the concentration of is controlled by the production, the decay, and the exchange and cycle of between atmosphere and other reservoirs such as oceans and the biosphere. The steady-state concentration is roughly 6 x 10 ° atoms of per gram of carbon in the pre-industrial atmosphere, and may vary slightly with time due to various reasons (see below). In simple calculations, the variation is ignored. In more accurate calculations, the variation must be taken into account. 

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