Chemistry of Life Matter and Energy: What are we made of?

Activity In your lab groups, draw on big paper a diagram of your atom--include and label: Protons and neutrons in nucleus Electrons by energy level ( “ shells ” ) Valence Electrons

What does the Periodic Table tell us?

Connecting Atom Structure to the Periodic Table Atomic No. = # of Protons (or # of Electrons in a neutral atom) Atomic Mass = Protons + Neutrons (average)

How to draw an atom: Neon Look at the periodic table How many protons? ______ How many electrons? ______ How many neutrons? _______

The nucleus Contains the protons and neutrons. Some atoms have different numbers of neutrons, we call these i sotopes. Isotopes give us average atomic mass. Radioactive isotopes lose nuclear particles over time and can be used for medical imaging.

What happens if you… Change the number of protons Change the number of electrons Change the number of neutrons

Connecting Atom Structure to the Periodic Table Rows = number of orbitals or shells Columns/Families = number of valence electrons (electrons in the outermost shell) Missing 58-71;90-103

Filling Electron Energy Levels Each energy level can hold a specific number of electrons: 1st level nd level rd level –8 When electrons levels are “ full ”, i.e. holding their maximum amount, then the atom is most stable or “happy”

Chemical Bonding Electrons are exchanged to fill outer energy levels The stability of atoms increases by completing their outer energy level Two types: IonicCovalent

Ionic bonds Ions are formed when atoms gain or lose electrons creating charged atoms Ionic Bonds are made between positive and negative ions. Cation - positive (+) Anion - negative ( - )

Practice Practice: If magnesium and oxygen formed an ionic bond, which atom would be the positive ion and which would be the negative ion?

Covalent Bonds Covalent bonds are made when atoms share electrons. Draw the shared electrons as a “ – ” How many covalent bonds can carbon form? Draw CH 4 A caffeine molecule has many covalent bonds

Electron diagrams Bohr Model – shows all electrons and each shell Lewis dot structures – shows only the valence electrons (only the outer shell)

Who can bond with who? Each element comes up and let ’ s see who they can bond with and what type of bond might form: Sodium-Neon Carbon-Hydrogen Chlorine-Oxygen Calcium

Polarity Sometimes atoms in molecules don’t share electrons evenly This creates positive and negative poles on the molecule (like a magnet) We call these molecules Polar molecules Ex. H 2 O