Easy Medium Hard Very hard Hydrogen (H2) Chlorine (Cl2) The coloured spheres represent different atoms and the plastic connectors are the bonds that join atoms together. Atoms can be joined together by bonds. Two or more of the same atom bonded together are called elements. Two or more different atoms bonded together are called compounds. The small number to the right of the atomic symbol is how many atoms of that element there are in that molecule TASK: Using the key on the other side of the sheet, can you build the molecules below, are they elements or compounds? Draw and label them in your books. Water has the formula H2O. That means it has 2 hydrogen (white) atoms and one oxygen (red) atom. It is a compound. Oxygen has the formula O2 That means it is made of 2 oxygen (red) atoms. It is an element. Easy Hydrogen (H2) Chlorine (Cl2) Hydrochloric acid (HCl) Medium Nitrogen (N2) Methane (CH4) Ammonia (NH3) Hard Carbon dioxide (CO2) Sulphur dioxide (SO2) Water (H2O) Very hard Ethanol (Alcohol) CH3-CH2-OH

Elements and compounds The coloured spheres represent different atoms and the plastic connectors are the bonds that join atoms together. . Carbon (C) atoms Hydrogen (H) atoms Oxygen (O) atoms Bonds Nitrogen (N) atoms Chlorine (Cl) atoms Sulphur (S) atoms