Basic Basic ChemistryChemistry

ReviewReviewAP BiologyAP 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 IdeasMain Ideas

Naturally Occurring Elements in the Human Body

Structure of an Structure of an AtomsAtoms

• Protons• Neutrons• Electrons -Found in

energy levels

NucleusNucleus

Each Energy Level Can Hold Each Energy Level Can Hold A Certain Numbers of A Certain Numbers of

Electrons!Electrons!Only Only TWO TWO on on the the first first levellevel!!

Different atoms have different Different atoms have different numbers of electrons!numbers of electrons!

Eight Eight on on the the 22ndnd and and 3rd 3rd levelslevels!!

Each Energy Level Can Hold Each Energy Level Can Hold A Certain Numbers of A Certain Numbers of

Electrons!Electrons!

Electrons can move from one energy level to another

• Atomic Atomic NumberNumber

• Number of Number of ProtonsProtons

1

1

•Atomic MassAtomic Mass

•Sum of Sum of Protons & Protons & NeutronsNeutrons

Periodic Table

IsotopesIsotopes 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 electronsatoms can gain or lose electrons

Cation

Anion

3P

3P3P

3P

3P

3P

atoms can gain or lose electronsatoms 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

Transfer of

electrons

from one

atom to

another

atom.

Occurs between

metals and nonmetals.Remember: Atoms need a full

outer energy level to be stable.

Bonding occurs with the valence electrons.

Occurs between metals and nonmetals.

Metals are electron donors.

Non-metals are electron accepters.

Called compounds.

OPPOSITS ATTRACT!

Ionic

Bondin

g

Covalent Bonding

The

sharing of

electrons

between

atoms.

Occurs between nonmetal

s and nonmetal

s.Called

Molecules.

Hydrogen and Fluorine

Hydrogen and Chlorine

Single, Double, Triple

Unequal Sharing

δ+

Polar

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 BondingHydrogen BondingWeak attraction between hydrogen and an electronegative atom such as oxygen and nitrogen taking part in a polar covalent bond.

A hydrogen bond

Hydrogen Hydrogen bonds in bonds in protein protein

structurestructure

Hydrogen Hydrogen bonds in DNA bonds in DNA

structurestructure

Chemical Reactions and Energy

• All chemical reactions release or absorb energy.– Heat, light, sound

• Chemical reactions are the making and breaking or bonds.

Chemical EquationsChemical Equations--show chem. rxnsshow chem. rxns..

2H2H22 + O + O22 2H 2H22OO Reactants:Reactants: substances that undergo substances that undergo

chemical reactions.chemical reactions. Products:Products: substance formed by chemical substance formed by chemical

reactions. reactions. Coefficient:Coefficient: shows the # of mol of each shows the # of mol of each

substancesubstance Subscript:Subscript: the # of atoms of each element in the # of atoms of each element in

the moleculethe molecule Ex. 2HEx. 2H22OO Ex #2: CEx #2: C1212HH2222OO1111

1. Exergonic

• Chemical reactions that releases energy are called exergonic.– 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 InhibitorsSome reactions proceed slowly.

•They can be sped up by a catalysts.– Catalysts are not used up in the reaction.– EX: enzymes (biological catalysts)

Some reactions proceed to fast.•They can be slowed down by

inhibitors.– EX: Preservatives in food

Photo- synthesi

s: a solar-

powered rearrangement

of matter