1. Chemistry of Life Chapter 2

2. Warm Up 8/20 Try to recall the following information without referencing your textbook or a friend What is an atom? What is an element? What differentiates one element from another? What are protons, neutrons and electrons?

3. Answers Atom: basic unit of matter Made up of 3 smaller particles Neutrons- no charge “neutral.” Found in nucleus Protons- positive charge. Found in nucleus Electrons- negative charge. Tiny. Orbit nucleus in a 3D “electron cloud” Element: a specific kind of atom Determined by number of PROTONS Examples?

5. Element name Atomic Number Element Symbol Atomic Mass

6. Atomic Number and Atomic mass Atomic Number Number of protons in that element Neutral atoms also have that same number of electrons Atomic mass Mass of protons and neutrons *usually about double the atomic number because there are typically the same number of protons and neutrons Summary For our purposes, a typical, stable atom has the same number of protons, neutrons and electrons

7. Bohr’s Atomic Model Nucleus in center (protons and neutrons) Electrons are in energy levels/energy shells surrounding the nucleus Energy level 1 holds up to 2 electrons Energy level 2 holds up to 8 electrons Energy level 3 holds up to 18 electrons

8. Stability and Octet Rule An atom is stable if its outer shell is full OR has eight electrons (octet rule) The outer shell is known as the VALENCE shell The number of electrons in the valence shell determines the reactiveness of the the element The closer to stable, the more reactive If the shell is full, the atom is non-reactive Noble gases

10. Let’s draw some atoms *list the number of valence electrons for each HydrogenHeliumOxygenNeonMagnesium

11. Unstable Atoms “like” to form bonds to become stable Ionic bonds Covalent bonds

12. Warm Up 8/20 Draw a fluorine atom How many valence electrons does it have? What does that say about its reactivity? Draw a fluorine ion How many valence electrons does it have? What does that say about its reactivity?

13. Today 8/22 Review ions Atoms that have gained/lost electrons Example: sodium ion Learn about ionic bonding Example: lithium chloride

14. Ionic Bonds Attraction between oppositely charged ions

15. Covalent Bonds Sharing of valence electrons