In the ScientificConstants package, the term "ScientificConstants object" refers to the objects returned by the Constant command applied to a physical constant or by the Element command applied to a property and an element (or isotope) of the periodic table.

There is a subset of commands that accept both physical constants and elements (or isotopes). However, some commands can be used with only physical constants and others with only elements and isotopes. The following sections give brief descriptions of the functionality available for elements and isotopes in the ScientificConstants package. For more information on these commands, see:

For details on the functionality available for physical constants, see Details of ScientificConstants Commands for Physical Constants.

For sample applications, see the example worksheet Applications of the ScientificConstants Package.

For references, see ScientificConstants References.

To access or represent the value of a property of an element of the periodic table, use the Element constructor.  For example, the atomic weight of sodium:

with(ScientificConstants):

Element( Na, atomicweight );

$\mathrm{Element}\left(\mathrm{Na}\,\mathrm{atomicweight}\right)$

For a list of elements in the ScientificConstants package, see Initial Elements of the Periodic Table.

With the Element constructor, a second argument specifying a property must be given. For a list of accepted properties, see Initial Properties for Elements and Isotopes

To obtain the value of a ScientificConstants object, use evalf with an element object.

evalf( Element( Na, atomicweight ) );

$3.817543727\times {10}^{\mathrm{-26}}$

Units:-UsingSystem();

$\mathrm{SI}$

The preceding element object was constructed without any reference to a system of units. Thus, when evaluated, it returns the property value in the current system of units. For more information about checking the current system of units, see Units[UsingSystem]. To evaluate it in a different system, first change the system of units with Units[UseSystem].

Units:-UseSystem( CGS );

evalf( Element( Na, atomicweight ) );

$3.817543727\times {10}^{\mathrm{-23}}$

To obtain a unit object that contains the units of the ScientificConstants object, use the GetUnit command. For more information about unit objects, see Units[Unit].

GetUnit( Element( Na, atomicweight ) );

$⟦g⟧$

Units:-UseSystem( SI );

GetUnit( Element( Na, atomicweight ) );

$⟦\mathrm{kg}⟧$

Again, the preceding element object is constructed without any reference to a system of units. Thus, it returns its units in the current system of units.

To construct an element object that always evaluates in a particular system of units, use the 'system' option.

Element( Na, atomicweight, system = Atomic );

${\mathrm{Element}}_{\mathrm{Atomic}}\left(\mathrm{Na}\,\mathrm{atomicweight}\right)$

evalf( (7) ),GetUnit( (7) );

$41907.81629,⟦\mathrm{em}⟧$

Notice that the preceding element object has the system of units in which it evaluates displayed in index notation.

By using the 'units' option, the element object is multiplied by the appropriate unit object. This is intended for use in the Standard Units environment.

Element( Na, atomicweight, units );

${\mathrm{Element}}_{\mathrm{SI}}\left(\mathrm{Na}\,\mathrm{atomicweight}\right)⟦\mathrm{kg}⟧$

evalf( (9) );

$3.817543727\times {10}^{\mathrm{-26}}⟦\mathrm{kg}⟧$

Element( Na, atomicweight, system = Atomic, units );

${\mathrm{Element}}_{\mathrm{Atomic}}\left(\mathrm{Na}\,\mathrm{atomicweight}\right)⟦\mathrm{em}⟧$

If the 'units' option is specified and the 'system' option is not specified, the current system is used.

For some elements, the value of a property is defined under different conditions than those for the majority of elements.  In such a case, the Element constructor returns an error, indicating how the value of the related property can be accessed.  For example, at standard pressure, which is the condition for the boiling point property, carbon has no liquid state and hence no boiling point.

Element( C, boilingpoint );

Error, (in ScientificConstants:-Element) no boiling point at standard pressure, access sublimation point with parameter 'sp'

Using the constructor with the parameter sp:

Element( C, boilingpoint(sp) );

$\mathrm{Element}\left(C\,\mathrm{boilingpoint}\left(\mathrm{sp}\right)\right)$

evalf((12));

$3915.$

Thus, for the element carbon, the property boilingpoint is said to be parameterized.  See Initial Properties for Elements and Isotopes and ScientificConstants[Element].

Many properties of elements have an associated uncertainty or error, which is a measure of the precision to which their values have been measured experimentally. For example, the atomic weight of sodium:

GetError( Element( Na, atomicweight ) );

$3.321080400\times {10}^{\mathrm{-33}}$

Some properties return an error of undefined, which indicates the error is implicit in the figures of the central value.

The errors returned for ScientificConstants objects are of numeric type and in absolute (not relative) form. That is, the magnitude depends on the system of units. For more information about uncertainties, see GetError.

To view information for an element in the ScientificConstants package, use the GetElement command.

GetElement( Na );

$11,\mathrm{symbol}=\mathrm{Na},\mathrm{name}=\mathrm{sodium},\mathrm{names}=\left\{\mathrm{sodium}\right\},\mathrm{boilingpoint}=\left[\mathrm{value}=1156.\,\mathrm{uncertainty}=\mathrm{undefined}\,\mathrm{units}=K\right],\mathrm{electronaffinity}=\left[\mathrm{value}=0.547926\,\mathrm{uncertainty}=0.000025\,\mathrm{units}=\mathrm{eV}\right],\mathrm{atomicweight}=\left[\mathrm{value}=22.989770\,\mathrm{uncertainty}=2.\times {10}^{\mathrm{-6}}\,\mathrm{units}=\mathrm{amu}\right],\mathrm{electronegativity}=\left[\mathrm{value}=0.93\,\mathrm{uncertainty}=\mathrm{undefined}\,\mathrm{units}=1\right],\mathrm{ionizationenergy}=\left[\mathrm{value}=5.1391\,\mathrm{uncertainty}=\mathrm{undefined}\,\mathrm{units}=\mathrm{eV}\right],\mathrm{meltingpoint}=\left[\mathrm{value}=370.87\,\mathrm{uncertainty}=\mathrm{undefined}\,\mathrm{units}=K\right],\mathrm{density}=\left[\mathrm{value}=0.97\,\mathrm{uncertainty}=\mathrm{undefined}\,\mathrm{units}=\frac{g}{{\mathrm{cm}}^3}\right]$

Note that an element can be identified by its atomic number (first item in the preceding sequence), symbol, or name(s). For example, any identifier can be used in the Element constructor.

To list the elements in the ScientificConstants package, use the GetElements command.

GetElements();

$H,\mathrm{He},\mathrm{Li},\mathrm{Be},B,C,N,\mathrm{O},F,\mathrm{Ne},\mathrm{Na},\mathrm{Mg},\mathrm{Al},\mathrm{Si},P,S,\mathrm{Cl},\mathrm{Ar},K,\mathrm{Ca},\mathrm{Sc},\mathrm{Ti},V,\mathrm{Cr},\mathrm{Mn},\mathrm{Fe},\mathrm{Co},\mathrm{Ni},\mathrm{Cu},\mathrm{Zn},\mathrm{Ga},\mathrm{Ge},\mathrm{As},\mathrm{Se},\mathrm{Br},\mathrm{Kr},\mathrm{Rb},\mathrm{Sr},Y,\mathrm{Zr},\mathrm{Nb},\mathrm{Mo},\mathrm{Tc},\mathrm{Ru},\mathrm{Rh},\mathrm{Pd},\mathrm{Ag},\mathrm{Cd},\mathrm{In},\mathrm{Sn},\mathrm{Sb},\mathrm{Te},I,\mathrm{Xe},\mathrm{Cs},\mathrm{Ba},\mathrm{La},\mathrm{Ce},\mathrm{Pr},\mathrm{Nd},\mathrm{Pm},\mathrm{Sm},\mathrm{Eu},\mathrm{Gd},\mathrm{Tb},\mathrm{Dy},\mathrm{Ho},\mathrm{Er},\mathrm{Tm},\mathrm{Yb},\mathrm{Lu},\mathrm{Hf},\mathrm{Ta},W,\mathrm{Re},\mathrm{Os},\mathrm{Ir},\mathrm{Pt},\mathrm{Au},\mathrm{Hg},\mathrm{Tl},\mathrm{Pb},\mathrm{Bi},\mathrm{Po},\mathrm{At},\mathrm{Rn},\mathrm{Fr},\mathrm{Ra},\mathrm{Ac},\mathrm{Th},\mathrm{Pa},U,\mathrm{Np},\mathrm{Pu},\mathrm{Am},\mathrm{Cm},\mathrm{Bk},\mathrm{Cf},\mathrm{Es},\mathrm{Fm},\mathrm{Md},\mathrm{No},\mathrm{Lr},\mathrm{Rf},\mathrm{Db},\mathrm{Sg},\mathrm{Bh},\mathrm{Hs},\mathrm{Mt},\mathrm{Ds},\mathrm{Rg},\mathrm{Cn},\mathrm{Uut},\mathrm{Fl},\mathrm{Uup},\mathrm{Lv},\mathrm{Uus},\mathrm{Uuo}$

GetElements( output=names )[30];

$\mathrm{zinc}$

GetElement( zinc );

$30,\mathrm{symbol}=\mathrm{Zn},\mathrm{name}=\mathrm{zinc},\mathrm{names}=\left\{\mathrm{zinc}\right\},\mathrm{boilingpoint}=\left[\mathrm{value}=1180.\,\mathrm{uncertainty}=\mathrm{undefined}\,\mathrm{units}=K\right],\mathrm{atomicweight}=\left[\mathrm{value}=65.39\,\mathrm{uncertainty}=0.02\,\mathrm{units}=\mathrm{amu}\right],\mathrm{electronegativity}=\left[\mathrm{value}=1.65\,\mathrm{uncertainty}=\mathrm{undefined}\,\mathrm{units}=1\right],\mathrm{ionizationenergy}=\left[\mathrm{value}=9.3942\,\mathrm{uncertainty}=\mathrm{undefined}\,\mathrm{units}=\mathrm{eV}\right],\mathrm{meltingpoint}=\left[\mathrm{value}=692.68\,\mathrm{uncertainty}=\mathrm{undefined}\,\mathrm{units}=K\right],\mathrm{density}=\left[\mathrm{value}=7.14\,\mathrm{uncertainty}=\mathrm{undefined}\,\mathrm{units}=\frac{g}{{\mathrm{cm}}^3}\right]$

To check the existence of an element in the ScientificConstants package, use the HasElement command.

HasElement( Na );

$\mathrm{true}$

HasElement( Sy );

$\mathrm{false}$

Elements can be added to the package using the AddElement command. For example, add "maplium".

AddElement(120, name = maplium, symbol = Sy);

HasElement( Sy );

$\mathrm{true}$

GetElement( Sy );

$120,\mathrm{symbol}=\mathrm{Sy},\mathrm{name}=\mathrm{maplium},\mathrm{names}=\left\{\mathrm{maplium}\right\}$

Element definitions can be modified or extended, for example, by adding a value for an accepted property.  To list the accepted element properties, use the GetProperties command.

GetProperties();

$\mathrm{atomicweight},\mathrm{boilingpoint},\mathrm{density},\mathrm{electronaffinity},\mathrm{electronegativity},\mathrm{ionizationenergy},\mathrm{meltingpoint}$

Now add the atomic weight to the element definition using the ModifyElement command.

ModifyElement( Sy, atomicweight= [value = 297, units = u] );

GetElement( 120 );

$120,\mathrm{symbol}=\mathrm{Sy},\mathrm{name}=\mathrm{maplium},\mathrm{names}=\left\{\mathrm{maplium}\right\},\mathrm{atomicweight}=\left[\mathrm{value}=297\,\mathrm{uncertainty}=\mathrm{undefined}\,\mathrm{units}=\mathrm{amu}\right]$

To add a new property to the element system, use the AddProperty command.

AddProperty( atomicradius );

GetProperties();

$\mathrm{atomicradius},\mathrm{atomicweight},\mathrm{boilingpoint},\mathrm{density},\mathrm{electronaffinity},\mathrm{electronegativity},\mathrm{ionizationenergy},\mathrm{meltingpoint}$

To check the existence of a property in the ScientificConstants package, use the HasProperty command. To check whether it is an element or isotopic property, use the GetProperty command.

HasProperty( atomicradius );

$\mathrm{true}$

GetProperty( atomicradius );

$\mathrm{atomicradius},\mathrm{isotopic}=\mathrm{false}$

For more information on isotopes, see the following section.