# Chemistry Notation in Questions

Although you can use standard HTML tags like <i> and <sup> to display correctly formatted chemistry notation in your questions, WebAssign provides several tags that can make displaying chemistry notation easier.

Note Do not combine the notation described in this topic with LaTeX or <symimage> markup.

## Displaying Chemical Formulas

You can use the <h:chemical> tag to display most chemical formulas correctly using a simplified notation that precedes subscripts with an underscore (_) and superscripts with a caret (^). See the following examples.

Example

Display

<h:chemical> H_2O </h:chemical>

H2O

<h:chemical> Ca^2+ </h:chemical>

Ca2+

<h:chemical> SO_4^2- </h:chemical>

SO42-

<h:chemical> [Co(SCN)_2(H_2O)_4]^+ </h:chemical>

[Co(SCN)2(H2O)4]+

## Displaying Isotopes

You can use the <watex> tag and its \over markup to display isotope mass numbers over atomic numbers. See the following example.

Example

Display

<watex> \over{233}{91}Pa </watex>

## Displaying Chemical Reactions

You can use the <h:reaction> tag to display most chemical reactions correctly using a simplified notation that precedes subscripts with an underscore (_) and superscripts with a caret (^), and replaces ->, <-, and <-> with reaction arrows. See the following examples.

Example

Display

<h:reaction> 2 H_2O_2 -> 2 H_2O + O_2
</h:reaction>

2 H2O2  2 H2O + O2

<h:reaction> N_2(g) + O_2(g) <-> 2 NO(g)
</h:reaction>

N2(g) + O2(g 2 NO(g)

<h:reaction> 4 NO(g) + O_2(g) <- 2 N_2O_3(g)
</h:reaction>

4 NO(g) + O2(g 2 N2O3(g)

Optionally, you can type either <s:revrxarrow> or &#8652; to display .

## Displaying Electron Configurations

You can use the <h:e-config> tag to display electron configuration notation correctly without having to indicate superscripts or italics. See the following examples.

Example

Display

<h:e-config> 1s2 2s2 2p5 </h:e-config>

1s2 2s2 2p5

<h:e-config> [He] 2s2 2p5 </h:e-config>

[He] 2s2 2p5

## Displaying Equilibrium Expressions

You can combine the <watex> tag and its \frac markup with the <h:chemical> tag to display equilibrium expressions with fractions. See the following example.

Example

Display

<watex>$K_b$ = \frac{ <h:chemical>[OH^- ]
<s:middot> [C_5H_5NH^+] </h:chemical> } {
<h:chemical>[C_5H_5N] </h:chemical> } </watex>
Tip
• In the <h:chemical>, <h:reaction>, <h:e-config>, and <watex> tags, you can display Perl variables without enclosing them in <eqn> or <EQN>. Just type the variable, for example, \$a, inside the tag where its value should be displayed. You might need to use a space to separate the variable name from any letters or numbers that follow it.
• You can add uppercase or lowercase Greek letters by typing <s:lettername> in your question, for example, <s:nu> for ν or <s:Delta> for Δ.