Guide to LaTeX (4th Edition) (Tools and Techniques

5.4. Additional elements 143
5.4.9 Chemical formulas and bold face in math formulas
In mathematics it is sometimes necessary to set individual characters or
parts of the formula in bold face. This can be achieved simply with the
math alphabet command \mathbf that we met in Section 5.4.2:
$\mathbf{Sˆ{-1}TS = dg(\omega_1,\ldots,\omega_n) = \Lambda}$
produces S −1 TS = dg(ω1, . . . , ωn) = Λ.
In this example, the entire formula has been set as the argument of
\mathbf so that everything should be set in bold face. In fact, only
numbers, lower and upper case Latin letters, and upper case Greek letters
are set in bold Roman with \mathbf. Lower case Greek letters and other
math symbols appear in the normal math font.
If only part of the formula is to be set in bold face, that part must be
given as the argument of the \mathbf command.
$\mathbf{2\sqrt{x}/y} = z$ 2 √ x/y = z
The math font style command \boldmath will set all characters in
bold face, with the following exceptions:
• raised and lowered symbols (exponents and indices)
• the characters + : ; ! ? ( ) [ ]
• symbols that exist in two sizes (Section 5.3.7)
The \boldmath declaration may not appear in math mode. It must
be called before switching to math mode or within a parbox or minipage.
The countercommand \unboldmath resets the math fonts back to the
normal ones.
\boldmath \[ \oint\limits_C V
V dτ = ∇ × V dσ \,\mathrm{d}\tau =\oint\limits_\Sigma
\nabla\times V\,d\sigma \] \unboldmath
C
Σ
If \boldmath has been turned on outside the math mode, it may be
temporarily turned off inside with \mbox{\unboldmath$. . . $}.
\boldmath\( P = \mbox{\unboldmath$m$}b\)\unboldmath
yields: P = mb. Similarly, \boldmath can be temporarily turned on
within math mode with the structure \mbox{\boldmath$. . . $}: Wr =
M dϕ = r 2 mω 2 /2
\( W_r = \int\mbox{\boldmath$M\,\mathrm{d}\varphi$} =..\)
An alternative method of printing single symbols in bold face is provided
by the bm package described on page 394.
Chemical formulas are normally set in Roman type, not in italics as
for mathematical formulas. This may be brought about by setting the
formula as the argument of the font command \mathrm:
$\mathrm{Fe_2ˆ{2+}Cr_2O_4}$ Fe 2+
2 Cr2O4