1. Atomic Structure Theories 9 SCIENCE

2. Dalton’s Atomic Theory  All Matter is made up of small particles called atoms.  All atoms of a particular element are identical in mass and size BUT are different from atoms of another element.  Compounds are created when different elements are combined chemically  Atoms cannot be created or destroyed or broken down into simpler particles  He thought an atom was an indivisible sphere like a billiard ball (pool ball)- an atom can’t be broken down any farther

3. Thompson’s Atomic Theory  All atoms are made up of small subatomic particles (protons and electrons because they are smaller than atoms) particles called protons and electrons.  All protons are identical, all electrons are identical but different from each other  Electrons= negative charge  Protons= positive charge  Protons have more mass  Atoms contain both protons & electrons- they have no charge

4. Thompson’s model:  Plum Pudding Model:  Pudding is positively charged dough, with negatively charged electrons (raisins) throughout.  Ex. Muffin- with little effort, you can take out the raisins (electrons)

5. Bohr’s Atomic Theory  Atom consists of a nucleus (tiny core that is very small volume but dense compared to the rest of the atom)  Nucleus contains protons  Atoms consists of an electron cloud around the nucleus ( larger in volume but less dense and lighter than nucleus- its also negative)  Believed electrons are located outside the nucleus

6. Bohr’s Model: 1 st shell- maximum of 2 electrons 2 nd shell- maximum of 8 electrons 3 rd shell-

7. Bohr- Rutherford’s Atomic Theory  Nucleus consists of protons (positively charged subatomic particles) and neutrons ( neutral, no charge)  Electrons are outside of the nucleus but are found in orbitals (paths) around the nucleus  The dotted lines are orbitals which are just paths the electrons travel around the nucleus  Nucleus- dense, contains protons& neutrons- takes up less space compared to the rest of the atom

8. Bohr –Rutherford continued…  This model is the one that we believe in today and its important to note that if we believe in this, then we disregard what Dalton said about the atom being the smallest particle of matter (we know that it contains protons, electrons,neutrons). However, Dalton was correct when he said that all atoms of one element are different than the other atoms of another atom.

9. Questions to do (use your book)  Define: law, theory, chemical formula, molecule, periodic table  How did the elements get their symbols?  List the properties of metals, non-metals and metalloids  How did Mendeleev build his periodic table?  Read pages 183-186, 190-194, 203-204 and 216-217