The abbreviations are used in chemistry to

What do the following symbol stand for:

$\mathrm{H}$

Write the symbol for the element :

 Oxygen.

Name the element for the following symbol.

Al

 Write the symbol for the element :

Gold.

Write the symbol for the element :

Calcium. 

What do the following symbol stand for:

$2\mathrm{H}$

What do the following symbol stand for:

${\mathrm{H}}_2$

Write the symbol for the element :

Iron.