The periodic table is a big list of all the elements that exist - all 118 of them to be precise. It is big enough already, but imagine how big it would need to be if every element was written out in full!
Rather than writing the full name of each element in the table, scientists have come up with symbols for each one. An element's symbol can be a single capital letter or a capital letter followed by a lower case letter.
Some of the elements have a symbol that is very much like its name, for example carbon has the symbol C and magnesium has the symbol Mg. But some elements' names have come from Latin, for example the Latin name for gold is aurum. So the symbol for gold is Au.
It's important to remember that the first letter of an element's symbol must be a capital letter. If the symbol has two letters, then the second one will be lower case.
Many non-metal elements are made of molecules, for example chlorine and oxygen. That means that there are two atoms of the element in each molecule.
Hydrogen has the formula H2. This means that a molecule of hydrogen contains two atoms of hydrogen joined together.
The little number two is key here. It tells us that hydrogen exists as a molecule rather than on its own.
And that's it! On to the questions ....
It might be helpful to have a paper copy of the periodic table in front of you because it can be hard to read the whole table on the screen. Otherwise a magnifying glass might be handy!!