Typography of Orbitals
In guidelines published by the International Union of Pure and Applied Physics or IUPAP$^{[1]}$, upright letters are recommended. Whether these letters are capitalised depends on their use. Lowercase is for quantum numbers of a single particle, and uppercase for describing a system.

A letter symbol indicating a quantum number of a single particle should be printed in lower case upright type.  A letter symbol indicating a quantum number of a system should be printed in capital upright type.$^{[1]}$

Almost identical text is found in the IUPAC Green Book.$^{[2]}$
The letters themselves ignoring capitalisation are $\mathrm{s}$ – sharp, $\mathrm{p}$ – principal, $\mathrm{d}$ – diffuse, $\mathrm{f}$ – fundamental, $\mathrm{g}$, $\mathrm{h}\ \ldots$
Continue according to the English alphabet skipping letter j.$^{[1]}$
In summary, for orbital angular momentum quantum numbers$^{[1]}$

\begin{align}\begin{split} l\ =\ &amp;0\ \ &amp;1\ \ &amp;2 \ \ &amp;3\ \ &amp;4\ \ &amp;5 \ \ &amp;6\ \ &amp;7\ \ &amp;8 \ \ &amp;9\ \ &amp;10\ \ &amp;11\ \ldots\\ \text{symbol}\ \ \ \  &amp;\mathrm{s}\ \ &amp;\mathrm{p}\ \ &amp;\mathrm{d}\ \ &amp;\mathrm{f}\ \ &amp;\mathrm{g}\ \ &amp;\mathrm{h}\ \ &amp;\mathrm{i}\ \ &amp;\mathrm{k}\ \ &amp;\mathrm{l}\ \ &amp;\mathrm{m}\ \ &amp;\mathrm{n}\ \ &amp;\mathrm{o}\end{split}\tag{for a single particle}\end{align}
\begin{align}\begin{split} L\ =\ &amp;0\ \ &amp;1\ \ &amp;2 \ \ &amp;3\ \ &amp;4\ \ &amp;5 \ \ &amp;6\ \ &amp;7\ \ &amp;8 \ \ &amp;9\ \ &amp;10\ \ &amp;11\ \ldots\\ \text{symbol}\ \ \ \  &amp;\mathrm{S}\ \ &amp;\mathrm{P}\ \ &amp;\mathrm{D}\ \ &amp;\mathrm{F}\ \ &amp;\mathrm{G}\ \ &amp;\mathrm{H}\ \ &amp;\mathrm{I}\ \ &amp;\mathrm{K}\ \ &amp;\mathrm{L}\ \ &amp;\mathrm{M}\ \ &amp;\mathrm{N}\ \ &amp;\mathrm{O}\end{split}\tag{for a system}\end{align}

As an example, here are two ways$^{[1]\ [2]\ [3]}$ of writing the predicted ground state electronic structure$^{[4]}$ of oganesson, element $118$:
$$\ce{Og: [Rn] {5f^{14}}{6d^{10}}{7s^2}{7p^6}\\ Og: [Rn] (5f)^14(6d)^10(7s)^2(7p)^6}$$
Typography regarding spacing is not explicitly stated, but is clear from the examples provided. Nevertheless, if you prefer to use
$$\ce{Og: [Rn] 5f^14 6d^10 7s^2 7p^6},$$
it should be fine as well.

$[1]$ E. Richard Cohen, Pierre Giacomo. $(1987)$. Symbols, Units, Nomenclature and Fundamental Constants in Physics. ('IUPAP Red Book'). International Union of Pure and Applied Physics. Commission C2 – Sunamco. ($2010$ reprint) (pp 12$-$13)
$[2]$ E. R. Cohen, T. Cvitas, J. G. Frey, B. Holmström, K. Kuchitsu,
R. Marquardt, I. Mills, F. Pavese, M. Quack, J. Stohner, H. L. Strauss, M. Takami, A. J. Thor. ($2007$). Quantities, Units, and Symbols in Physical Chemistry. ('IUPAC Green Book'). Third Edition. International Union of Pure and Applied Chemistry. ($2008$ IUPAC &amp; RSC reprint). ISBN: 978-0-85404-433-7. (p 32)
$[3]$ Anne M. Coghill, Lorrin R. Garson. ($2006$). The ACS Style Guide. Effective Communication of Scientific Information. American Chemical Society. DOI: 10.1021/bk-2006-STYG, ISBN: 9780841239999 (print), 9780841228306 (online). (p 256)
$[4]$ 'The Element Oganesson'. $(2016)$. Steve Gagnon. Thomas Jefferson National Accelerator Facility – Office of Science Education. (February 1, 2017)