1. Atoms, Elements, and the Periodic Table Ch. 17 & 19 Ch. 17 Section 1 Structure of the Atom

2. Warm Up Diagram an atom. Include protons, neutrons, quarks, and the electron cloud.

3. Atoms An element is matter with a fixed composition – it is made of the same atoms An atom is the smallest piece of matter that still retains the properties of its element.

4. Atoms The main particles that compose an atom are: –Protons: positively charged –Neutrons: neutrally charged –Electrons: negatively charged Protons and neutrons are found in the center of the atom - the nucleus Electrons are found orbiting in the electron cloud surrounding the nucleus

5. Atoms Protons and neutrons are made up of smaller particles called quarks Two up-quarks and a down-quark produce a proton, while two down-quarks and an up-quark produce a neutron

6. Atoms The electron cloud model of an atom is used today The electron cloud is the area around an atom’s nucleus where electrons are found The electron cloud is 100,000 times larger than the diameter of the nucleus, but electrons are much smaller than both protons and neutrons

7. Subatomic Particle Masses & Charges ParticleMass (g)Mass (atomic mass unit - amu) Charge Proton 1.67 x 10 -24 1+1 Neutron 1.67 x 10 -24 10 Electron 9.11 x 10 -28 <<1

8. Atoms The mass of an atom comes from particles in its nucleus The electron is so small, it is considered negligible when finding the mass of an atom

9. Atoms The unit of measurement used for atomic particles is the atomic mass unit (amu)

10. Masses of Atoms An atom’s atomic number is equal to the number of protons in an atom An atom’s mass number is the sum of the protons and neutrons in an atom 11 Sodium Na Na 22.98976928

11. Atomic Mass The mass of a proton or a neutron is approximately 1 amu A chlorine atom containing 17 protons and 18 neutrons has a mass of 35 amu

12. Masses of Atoms Copper (Cu) has an atomic number of 29 and a mass number of 64 29 amu of its mass comes from its 29 protons The remaining 35 amu comes from its 35 neutrons 29 Cu Copper 63.5

13. Masses of Atoms Atoms of the same element can have different numbers of neutrons These are isotopes Isotopes are identified by the name of the element followed by its mass number

14. Masses of Atoms Carbon-12 has 6 protons and 6 neutrons Carbon-14 has 6 protons and 8 neutrons The average atomic mass of an element is the weighted average mass of the element’s isotopes

15. Atomic Structure Energy levels are the level at which electrons orbit the nucleus They are numbered from the inside to the outside The first level can contain a maximum of 2 electrons, the second 8 electrons, the third 18, and the fourth 32

16. The Bohr Model The Bohr Model of an atom shows all its electrons in their specific energy levels. Energy level maximums are: 2, 8, 18, 32 Numbers can repeat and go back down, but cannot skip The outer energy level has a maximum of 8 electrons

17. The Bohr Model Argon has 18 electrons. 2 are in the first energy level, 8 in the second, and the remaining 8 are in the third.