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Chemical and Isotope Data

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The ScientificConstants package contains chemical data

Use the GetElement command to access the properties of elements in the Periodic Table. For example, let's review the properties of Platinum (Pt).







You can also extract the standard atomic weight of platinum.

evalfElementPt, atomicweight,units



With the GetIsotopes command, you can access all instances of platinum.





Example - Molecular Weight


This example determines how many molecules of caffeine are in a 250 gram sample.


The chemical formula for caffeine is C8H12N4O2.  Thus, the molecular weight is:


MW  8ElementC, atomicweight+12ElementH,atomicweight+4ElementN,atomicweight+2ElementO,atomicweight: evalfMW




which, in the current default system of units, SI, is measured in kilograms (kg). However, molecular weight is typically expressed in atomic mass units (amu). To convert a measurement between units, use the convert/units function.

MW__AMUconvertMW, units, kg, amu




By definition, the number of atomic mass units per molecule is equal to the number of grams per mole. Hence, divide 250 by the above result.

NumMoles   250MW__AMU



which is the number of moles in the sample.


To calculate the number of molecules, multiply the above result by Avogadro's constant.





Example - Radioactive Decay

The following example shows how to plot the decrease in the radioactive decay activity for a sample of radium-229.


The activity is

Activity  A0ⅇλt:

where, A0 is the initial activity, λ is the mean lifetime of the isotope, and t is the elapsed time.

The mean lifetime is related to the half-life by λ=0.693H

λ  0.693evalfElementRa229, halflife




Plot with A0=1.

A01:plotActivity, t=0..2103, labels=Time (s), Activity, title=Radioactive Decay of Radium-229