2 ISOTOPES EVERY CHLORINE ATOM HAS 17 PROTONS, WITHOUT EXCEPTION, HOWEVER, NOT EVERY CHLORINE ATOM HAS NEUTRONS.ATOMS WITH THE SAME NUMBER OF PROTONS BUT CONTAIN DIFFERENT NUMBERS OF NEUTRONS ARE CALLED ISOTOPES.BECAUSE ISOTOPES OF AN ELEMENT HAVE DIFFERENT NUMBERS OF NEUTRONS THEY HAVE DIFFERENT MASS NUMBERS.
3 ISOTOPES ARE CHEMICALLY ALIKE BECAUSE THEY HAVE IDENTICAL NUMBERS OF PROTONS AND ELECTRONS IT’S THE ELECTRONS AND PROTONS THAT ARE RESPONSIBLE FOR CHEMICAL BEHAVIORBERYLLIUMISOTOPESprotonneutronelectron
4 Cl Cl 18 20 EXAMPLE OF AN ISOTOPE 35 37 17 17 ATOMIC MASS NEUTRONS ATOMIC NUMBER18NEUTRONS20NEUTRONS
5 IONS AN ELEMENT’S ATOMS ARE NOT ALWAYS NEUTRAL IN CHARGE. WHEN AN ATOM LOSES OR GAINS ONE OR MORE OF ITS ELECTRONS IT BECOMES ION.AN ION THAT HAS MORE ELECTRONS THAN PROTONS HAS A NEGATIVE ELECTRICAL CHARGEAN ION THAT HAS FEWER ELECTRONS THAN PROTONS HAS A POSITIVE ELECTRICAL CHARGENOTE: IT’S THE PROTONS THAT DEFINE THE TYPE OF ATOM IT IS, BUT THE ELECTRONS DEFINE THE ATOM’S CHARGE.
6 SOME ATOMS GAIN ELECTRONS ATOM’S IONIC CHARGE =# PROTONS - # ELECTRONS------------------OO-2
7 The Nerve CellsSodium and potassium ions are used in the transmission of a nerve impulse.
8 Chemical Reactions Ø Chemical equations represent chemical reactions Ø Living things undergo thousands of chemical reactionsØ Chemical equations represent chemical reactionsØ CO2 + H goes to-----H2CO3 (carbonic acid) is a sample Chemical Reaction in living thingsØ Reactants are on the left side of the equation, while products are on the right side
9 Activation energy is required to start many reactions Energy must be added to the reactants for most chemical reactions to occur; called activation energy
10 EnzymesEnzymes are chemical substances in living things that act as catalysts & reduce the amount of activation energy neededOrganisms contain thousands of different enzymesMost enzymes end with –ase (e.g. lipase is the enzyme that acts on lipids)
12 Physical Properties of Water All of water’s UNIQUE properties are due to its POLARITY and HYDROGEN BONDINGPOLARITYH2O is a NEUTRAL molecule (p+ = e-)Oxygen attracts most of the e- toward its end and away from the hydrogenThe OXYGEN END acts NEGATIVE, while the HYDROGEN END acts POSITIVE POLARITY (unequal distribution of charge)
13 HYDROGEN BONDINGNegative OXYGEN of ONE H2O molecule attracts the Positive HYDROGEN of ANOTHER H2O molecule
14 Bonding StrengthsTrue chemical bonds like covalent, ionic, and metallic bonds are the strongest bondsCovalent bonds are the strongest force of attraction. They are stronger than ionic and metallic bonds.Hydrogen Bonding is a weaker type of bonding because it’s between molecules.
15 Acids and BasesThe degree of acidity or alkalinity (basic) is important in organismsThe force of attraction between molecules is so strong that the oxygen atom of one molecule can actually remove the hydrogen from other water molecules; called DissociationH GOES TO----- H+ + OH-OH- called hydroxide ion; H+ called hydrogen ion
16 Free H+ ion can react with another water molecule to form H3O+ (hydronium ion) Acidity or alkalinity is a measure of the relative amount of H+ and OH- ions dissolved in a solutionNeutral solutions have an equal number of H+ and OH- ionsAcids have more H3O+ ions than OH- ions; taste sour; and can be corrosiveBases contain more OH- ions than H3O+ ions; taste bitter; & feel slippery
17 PH Scale Compares the relative concentration of H3O+ ions and OH- ions Scale ranges from 0 to 14; 0-3 is very acidic; 7 is neutral; is very basic or alkaline
18 Buffers Control of pH is important to organisms Enzymes function only within a narrow pH range; usually neutralBuffers neutral acids or bases in organisms to help control pH
19 Organic MoleculesOrganic Compounds - have carbon bonded to other atoms (mostly Hydrogen) and determine structure/function of living thingsInorganic Compounds – all othersOrganic compounds are made from a carbon skeleton which canvary in length,be branched or unbranchedhave double bonds which vary in locationor may be arranged in rings.
20 Types of Organic Molecules MACROMOLECULES fall into four major groups1. Carbohydrates 2. Lipids 3. Proteins 4. Nucleic Acids