Chemistry Notes outline Elements found in humans= organic= Atom structure A. nucleus (protons, neutrons) B. Electrons (levels, valence) Mass vs. Atomic # Table Compounds a. Ionic bonds b. Covalent bonds VI. Orbital drawings

Why study chemistry in biology class? We need to know the makeup of living things before trying to understand them Chemical reactions are always occurring in the body

Section 6.1 Summary – pages 141-151 Elements All things (living and nonliving) – whether it is a rock, frog, or flower – are made of substances called elements. Element—a substance that can’t be broken down into simpler chemical substances. Section 6.1 Summary – pages 141-151

Elements Examples—gold, carbon, hydrogen, oxygen, and nitrogen. If pure gold is ground into pieces, it is still gold.

Elements Humans contain: C, H, O, N which makes up > 96% of our bodies All living things contain carbon = organic!!

Section 6.1 Summary – pages 141-151 Atoms: The Building Blocks of Elements All elements are made up of atoms. Atom—the smallest particle of an element that has the characteristics of that element.

The structure of an atom Nucleus—the center of an atom Proton—positively charged particles inside the nucleus Neutrons—Neutral (no charge) particles inside the nucleus Protons Neutrons Nucleus

Section 6.1 Summary – pages 141-151 Electron energy levels Nucleus 8 protons (p+) 8 neutrons (n0) Electrons—extremely small particles with negative charge located in electron cloud Oxygen atom 1st energy level—maximum 2 electrons 2nd energy level—maximum 8 electrons 3rd energy level—maximum 18 electrons Section 6.1 Summary – pages 141-151

The Structure of an atom Valence electrons: electrons in outer energy level Atoms contain—equal numbers of protons and electrons so they have no charge

Periodic Table of Elements—Displays the elements and their symbols Atomic mass = weight of nucleus (protons and neutrons); big number on periodic table Atomic number = # protons = # electrons; little number on periodic table

In summary Type of particle Location Charge Symbol How many? Proton nucleus positive P+ Atomic # Neutron Nucleus Neutral n° Atomic mass - # Electron Energy levels Negative E-

Compounds Compounds—A substance made up of atoms of 2 or more elements Water molecule 2 hydrogen atoms 1 oxygen atom

Chemical bonds Atoms are stable when outermost energy level is full In order to become stable atoms with either gain/lose or share electrons Ionic bond: electrons transferred from one atom to another Covalent bond: atoms share electrons Very strong bond

Orbital drawings—diagram of an atom with its electrons arranged around the nucleus # of protons— 7 # of neutrons— 7 # of electrons— 7

Make an orbital drawing for fluorine (F)-- Fill in the #’s of protons and neutrons, all of the electrons, and label the nucleus and energy levels. # of protons— # of neutrons— # of electrons—

Let’s Practice We’ll draw chlorine (17, 35) and sodium (11, 23) bonding:

Who wants to draw on the board? Beryllium 4 9

Another volunteer? Argon 18 40

One more Aluminum 13 27