The Chemical Level of Organization Atoms Atomic Structure Electron Shells, losing/gaining electrons Ions Molecules, their formation through bonds Chemical Bonds (how, why, and types) Macromolecules 4 major macromolecules

Elements & Atoms

Elements Different kinds of matter (material) that have distinct (chemical) properties Examples: gold carbon hydrogen sodium nitrogen calcium oxygen

many different object/pictures 5 basic shapes

Atoms Smallest unit/piece of an element (matter) that still has the properties of that element. TAKE A BAR OF GOLD/IRON AND BREAK IT UP INTO THE SMALLEST BIT THAT IS STILL IRON/GOLD THAT WOULD BE AN ATOM WRITE THE 3 PARTICLES AND 2 REGIONS ON THE BOARD

The structure and components of an atom --Neutral --positive --negative EXPLAIN AND WRITE ABOUT ELECTRON SHELLS SHOW HOW MANY THE FIRST 4 HOLD EXPLAIN VALANCE SHELLS--OUTERMOST

Electron Shell (orbital) Proton Neutron Electron Electron Shell (orbital) Nucleus

Different elements are made of atoms with different numbers of protons and electrons—that is why each element has its own unique set of properties 2p, 2e, Helium 4p, 4e, Beryllium 3p, 3e, Lithium

Element Number of protons Number of electrons % of Body by Weight Hydrogen 1 9.5 Carbon 6 18.5 Nitrogen 7 3.3 Oxygen 8 65.0 Sodium 11 0.2 Sulfur 16 0.3 Chlorine 17

Valence Shells outermost shell of atom = valance shell Atoms are most stable when the outer shell is filled, or emptied. Valance shells

Electron shells of common elements Valance in red 1st shell 2nd shell 3rd shell 4th shell Hydrogen 1 Carbon 2 4 Nitrogen 5 Oxygen 6 Sodium 8 Chlorine 7 Potassium calcium TALK ABOUT ATOMIC ‘STABILITY’ AND VALANCE SHELLS ATOMS WILL LOSE, GAIN OR SHARE ELECTRONS TO FILL OR EMPTY THEIR OUTERMOST SHELLS THIS IS THE BASIS FOR ION FORMATION AND FOR CHEMICAL BONDING USE Na, CL, K, AND Ca AS EXAMPLES

Behavior of atoms and outer electron shells Atoms “want” to have completely emptied or completely filled outer electron shells. Atoms will gain, lose, or share electrons to fill or empty their outer shells. This is the basis for chemical bonds and the formation of ions

electron shell = orbital = valence shell = regions that hold electrons

Formation of ions

Gaining or Losing Electrons Gaining Electrons If the outer shell is almost full, gaining electrons is likely to happen Losing Electrons If the outer shell is almost empty, losing electrons is likely to happen 1- 1+ Note that both of these events will result in the creation of an ion.

Atoms lose an electron and become a positive ion. Atoms gain electrons and become a negative ion. 4 protons: 4+ 5 electrons: 5- Charge: 1- 4 protons: 4+ 3 electrons: 3- Charge: 1+

(not from your text) NOTE THAT WHOLE MOLECULES CAN ALSO BE IONIZED--

Functions of Ions Generate Electricity (membrane potentials) e.g., neurons of your brain and nervous system (sodium, potassium, and calcium) Regulate/initiate cellular events e.g., help initiate muscle contraction, release of neurotransmitters, expression of DNA, activate enzymes (calcium), blood clotting Building materials e.g., Calcium (and phosphate) is part of bones Regulate pH/acidity HCO3- (bicarbonate ion)

CHEMICAL BONDING AND MOLECULES

CHEMICAL BONDING Two or more atoms can bind together to form a molecule. There are 3 major types of chemical bonds Ionic Bonds Covalent Bonds Hydrogen Bonds Create molecules do NOT create molecules

Ionic Bonds WRITE ON BOARD WHAT AN IONIC BOND IS: BOND DUE TO THE ATTRACTION OF OPOSITE CHARGES

Formation of an Ionic Bond Ionic bonds are usually formed when two atoms happen to be in close proximity and exchange electrons and become oppositely charge ions. The atoms are then held together by the attraction of opposite charge Strength:

Covalent Bonds BOND FORMED WHEN ATOMS SHARE ELECTRONS TO FILL THEIR OUTER SHELLS

When an electron pair is shared, both atoms get to “count” the other atom’s electron as if it was part of their own valance shell.

Covalent Bonds: Atoms share electrons Strength:

Polar and Non-polar Bonds/Molecules Non-Polar = electrons are shared equally the entire molecule is neutral and uniformly charged. Tends to mix well with other non-polar substances Don’t mix well with water Polar = electrons are not shared equally then entire molecule is neutral overall, but has regions/areas that are + or – charged Tends to mix and dissolve well with other polar things LIKES WATER/mixes with water WATER IS AN IMPORTANT POLAR MOLECULE

Polar (and charged) Hydrophilic Water soluble nonpolar Not water soluble (lipid soluble) Hydrophobic

Hydrogen bonds ATTRACTION BETWEEN A HYDROGEN AND AN OXYGEN OR NITROGEN CAUSED BY POLAR CHARGES

Hydrogen Bonds Are attractive forces between a hydrogen and an oxygen or a hydrogen and a nitrogen NOT based on electron transfer or sharing Hydrogen bonds can exists between: 1. two different molecules--resulting in their being held together. two different parts of the same molecule— resulting in the bending/folding of the molecule. But hydrogen bonds don’t create molecules the way that a covalent or ionic bond does.

Comments on H-bonds individual hydrogen bonds are weak, the collective influence of many hydrogen bonds can be significant The bending of molecules with hydrogen bonds creates the final 3D shape of proteins Form between water molecules Hold DNA strands together H-bonds are weak bond formed between two polar molecules based on opposite charges attracting (not based on electron sharing)