Basic Chemistry Review AP Biology

Why are we studying chemistry????

2. Atoms combine by chemical bonding to form molecules 1.Matter consists of chemical elements in pure form and in combinations called compounds 3. Weak chemical bonds play important roles in the chemistry of life 4. A molecule’s biological function is related to its shape 5. Chemical reactions result from making and breaking chemical bonds Main Ideas

Naturally Occurring Elements in the Human Body

Structure of an Atoms Protons Neutrons Electrons -Found in energy levels Nucleus

Each Energy Level Can Hold A Certain Numbers of Electrons! Only TWO on the first level!

Different atoms have different numbers of electrons! Eight on the 2 nd and 3rd levels! Each Energy Level Can Hold A Certain Numbers of Electrons!

Electrons can move from one energy level to another

Atomic NumberAtomic Number Number of ProtonsNumber of Protons 1 1 Atomic MassAtomic Mass Sum of Protons & NeutronsSum of Protons & Neutrons Periodic Table

Isotopes Isotopes are atoms that have the same number of protons and differ only in the number of neutrons. Most isotopes are stable but radioactive isotopes are unstable and break down into more stable forms by emitting particles and energy (radiation). Radiation can be detected, so radioactive isotopes are useful as labels in scientific research and medical diagnostic procedures.

Radioactive isotopes are used to diagnose medical disorders. (C-11, F-18, O-15) –Radioactive tracers can be used with imaging instruments to monitor chemical processes in the body.

atoms can gain or lose electrons Cation Anion 3P

atoms can gain or lose electrons Ionization: requires energy Why do atoms lose and gain electrons? To become more stable. Stability=full outer energy level

Why do Atoms Form Compounds? Stability. What makes an atom stable? Full outer energy level. Eight.

How can atoms become stable? Gain or lose electrons. Share electrons.

A Chemical Bond holds atoms together in a compound. Two basic typesTwo basic types: Ionic Covalent

Ionic Bonding T r a n s f e r o f e l e c t r o n s f r o m o n e a t o m t o a n o t h e r a t o m. O c c u r s b e t w e e n m e t a l s a n d n o n m e t a l s. Remember: Atoms need a full outer energy level to be stable. Bonding occurs with the valence electrons.

O c c u r s b e t w e e n m e t a l s a n d n o n m e t a l s. M e t a l s a r e e l e c t r o n d o n o r s. N o n - m e t a l s a r e e l e c t r o n a c c e p t e r s. C a l l e d c o m p o u n d s.

OPPOSITS ATTRACT!

Covalent Bonding T h e s h a r i n g o f e l e c t r o n s b e t w e e n a t o m s. O c c u r s b e t w e e n n o n m e t a l s a n d n o n m e t a l s. C a l l e d M o l e c u l e s.

Hydrogen and Fluorine Hydrogen and Chlorine

Single, Double, Triple

Unequal Sharing δ+δ+ Polar δ_δ_

Polar covalent bonds in a water molecule

Covalent Bonds The attraction of electrons to an atom is called electronegativity. The more electronegative an atom, the more a shared electron is pulled towards its nucleus. If two atoms are of the same element or of the same electronegativity, the pull of the electron is equal and the bond is a NONPOLAR covalent bond. POLAR covalent bonds form when one atom is more electronegative than another; thus, the electron is pulled closer to the atom with the high + charge…forming poles.

Hydrogen Bonding Weak attraction between hydrogen and an electronegative atom such as oxygen and nitrogen taking part in a polar covalent bond.

A hydrogen bond

Hydrogen bonds in protein structure

Hydrogen bonds in DNA structure

Chemical Reactions and Energy All chemical reactions release or absorb energy. –H–Heat, light, sound Chemical reactions are the making and breaking or bonds.

Chemical Equations -show chem. rxns. 2H 2 + O 2  2H 2 O 2H 2 + O 2  2H 2 O  Reactants: substances that undergo chemical reactions.  Products: substance formed by chemical reactions.  Coefficient: shows the # of mol of each substance  Subscript: the # of atoms of each element in the molecule  Ex. 2H 2 O  Ex #2: C 12 H 22 O 11

1. Exergonic Chemical reactions that releases energy are called exergonic. –G–Glow sticks If heat is released, it is called exothermic.

2. Endergonic Chemical reactions that require energy are called endergonic. Ex: Cold Packs If heat is absorbed, it is called endothermic

Oxidation-Reduction Rxns Transfer electrons from one reactant to another Loss of electrons – oxidation Gain of electrons – reduction Ex. Xe - + Y  X + Ye - (X is the electron donor, so reducing agent; Y is the electron acceptor, so oxidizing agent.)

Catalysts and Inhibitors Some reactions proceed slowly. They can be sped up by a catalysts. –C–Catalysts are not used up in the reaction. –E–EX: enzymes (biological catalysts) Some reactions proceed to fast. They can be slowed down by inhibitors. –E–EX: Preservatives in food

Photo- synthesis : a solar- powered rearrange ment of matter