> I'm not sure what formula is suppose to be.
Formula is a tab that allows you to build molecules or ionic compounds, and then get information or do some math. You can modify the default molecule using the "+" icon on the left, to add elements, or the edit button on the right to for example change charge or subscripts. You can start from scratch by using the bin button on the right, and choose molecules / compounds by name by using the edit button after having selected the outermost rectangle (the one that is highlighted in green). Please tell me if there are some parts that aren't clear, I'd be happy to explain.
> The app is missing elements
Hm, I'm not sure I see which ones are missing.. We followed the IB booklet (http://www.ibchem.com/root_pdf/data_booklet_2016.pdf
, see page 10), and I'm not aware of any elements we could add.
Thanks for the feedback !