Elements, compounds, symbols and formula

1. Elements, compounds, symbols and formula

2. We have already learned that... • Elements are: a pure substance that cannot be broken into simpler parts by ordinary chemical means. • There are 114 elements • Compounds are:a pure substance made up of two or more elements, chemically combined in fixed proportions • there are millions of known compounds

3. Elements: hydrogen copper uranium Compounds: water copper (II) sulfate plastic Examples of Elements and compounds

4. Scientists have devised a ‘short hand’ way of naming elements these are called chemical symbols hydrogen = H carbon = C calcium = Ca Many symbols are the first letter of the element…carbon others are the first two letters, like calcium others use two prominent letters like cadmium…Cd still others use latin, greek or other language roots, like copper Cu (cuprium) Elements and Symbols

5. Whatever the reason for naming an element, the same rules apply only one capital letter if the symbol is two letters, it must be one upper and one lower case letter The newest of the synthetic elements have three letters, Uub for example eventually when element 112 is named it will be given a two letter symbol Elements and Symbols

6. Compounds also have a short hand way of naming them these are called chemical formula H2O is a familiar example CO2 = carbon dioxide C6H12O6 = glucose H2O2 = hydrogen peroxide CuSO4 = copper sulfate Compounds and formula

7. Like symbols, formula have certain rules for their use. They always contain the elements found in the compounds they always show the relative number of atoms of each element For example: H2O tells us many things about water… the fact that it is made up of hydrogen and Oxygen the fact that there are 2x as many hydrogen atoms as oxygen atoms Chemical formula

8. From this you should be able to see why it is so important to follow the naming rules for elements Use “CO” as an example Is this an atom of Cobalt or a compound of Carbon Oxide? Because we know that symbols (elements) can never be two upper case letters, this must be Carbon Oxide In fact it is called carbon monoxide, a deadly gas! Chemical Formula