Let’s Talk Chemistry!

1. The Atom  basic unit of matter  made up of protons, neutrons and electrons  the atom is neutrally charged (no charge) Helium Atom: Atomic Number 2 Electron Proton Neutron

2. Structure of an atom The nucleus of an atom:  Protons are positively charged  Neutrons have no charge Electrons:  in constant motion around nucleus  negatively charged Atoms have an equal number of protons and electrons.

3. Elements  Pure substance  Made of one type of atom  Represented by 1, 2 or 3 letters

4. History of the Periodic Table  Mendeleev designed the first periodic table  He arranged the elements by increasing atomic mass  He left blank spaces according to similarities in columns of elements

More history…  Mendeleev’s blank spaces (or predictions) were elements that he claimed were not discovered yet.  As it turns out, he was right!!  Scientists later discovered the missing elements with the properties that Mendeleev predicted!

And even more history!  Moseley discovered the atomic number  He organized the periodic table by increasing atomic number  This allowed for elements with similar properties to fall into place  An gave way to the modern periodic table

5. Molecules  Smallest unit (part) of a compound  Hydrogen molecule Hydrogen molecule Water

6. Compounds  a substance that contains two or more different elements  organic compounds must contain Carbon Acetic acid

Molecular formula 7. Molecular formula  Shows how many atoms of each element a molecule contains  Does not tell you about a molecule’s structure

Examples of molecular formulas H2O2 hydrogen 1 oxygen NH31 nitrogen 3 hydrogen C6H12O66 carbon 12 hydrogen 6 oxygen

8. Structural formula  Shows how atoms are arranged in a molecule  2-dimensional representation of a molecule’s structure

9. 3-D model  Shows how the atoms are arranged in a molecule  Is able to be moved or turned, allowing you to view the molecule from different angles  3D model 3D model