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Chapter 2 Matter and Energy Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Matter and Energy Matter—anything that occupies space and has mass Energy—the ability to do work (for biologists, it includes-) Chemical energy Mechanical energy Heat Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings All matter is composed of atoms About 120 elements, 91 occur naturally 96% of the body is made from four elements Carbon (C) Hydrogen (H) Oxygen (O) Nitrogen (N) CHON Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings All matter is composed of atoms CHON Other elements in the body include: Ca, P, K, S, Na, Cl, Mg, I, Fe Trace elements include: Cr, Cu, Co, F, Mn and others Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Atomic Structure – Subatomic particles Name Symbol Mass Charge Location Proton Neutron Electron Figure 2.1 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Atomic Structure – Subatomic particles Name Symbol Mass Charge Proton p 1 amu +1 Neutron n 1 amu 0 Electron e- 0 amu -1 Location in nucleus in nucleus around nucleus, in electron cloud Figure 2.1 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Atomic Structure Figure 2.1 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Atomic Structure of Smallest Atoms Electrons have different energy levels. Only the outer level affects an atom’s chemical properties! Figure 2.2 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Identifying Elements Atomic number —equal to the number of protons Atomic mass number —sum of the protons and neutrons Atomic Number = number of protons Name 19 39.0983 K Average atomic mass, in amu/atom Potassium Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Symbol Identifying Elements Name Symbol Atomic Number Atomic Mass Number #p #n (most likely) Sulfur K 20 17 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings # e- Identifying Elements Name Symbol Atomic Number Atomic Mass Number #p #n # e- (most likely) Sulfur S 16 32 16 16 16 Potassium K 19 39 19 20 19 Calcium Ca 20 40 20 20 20 Chlorine Cl 17 35 17 18 17 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Isotopes and Mass Number Isotopes Have the same number of protons Vary in number of neutrons Figure 2.3 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Isotopes and Mass Number Chlorine has two common isotopes, Cl-35 and Cl-37 Figure 2.3 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Isotopes and Mass Number Chlorine has two common isotopes, Cl-35 and Cl-37 How many neutrons in each? Figure 2.3 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Isotopes and Mass Number Chlorine has two common isotopes, Cl-35 and Cl-37 How many neutrons in each? How many protons in each? Figure 2.3 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Isotopes and Mass Number Chlorine has two common isotopes, Cl-35 and Cl-37 How many neutrons in each? How many protons in each? Which one is more common? Figure 2.3 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Isotopes and Mass Number Chlorine has two common isotopes, Cl-35 and Cl-37 How many neutrons in each? 18 and 20 How many protons in each? 17 Which one is more common? Cl-35 Figure 2.3 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Isotopes and Average Atomic Mass Average atomic mass Usually closest to mass number of most abundant isotope Average atomic mass reflects natural isotope variation Take the average atomic mass and round to the nearest whole number for the mass number of the most common isotope Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Isotopes and Average Atomic Mass The periodic table is arranged by atomic number. The average atomic mass usually increases with atomic number. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Isotopes and Average Atomic Mass The periodic table is arranged by atomic number. The average atomic mass usually increases with atomic number. Find 3 exceptions. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Isotopes and Average Atomic Mass The periodic table is arranged by atomic number. The average atomic mass usually increases with atomic number. Find 3 exceptions. Why does this (rarely) occur? Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Isotopes and Average Atomic Mass The periodic table is arranged by atomic number. The average atomic mass usually increases with atomic number. Find 3 exceptions. Why does this (rarely) occur? Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Radioactivity—process of spontaneous atomic decay Radioisotopes are radioactive Typically an unusually heavy isotope Tend to be unstable Decompose to more stable isotope Used in medical diagnosis and treatment Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Compounds Elements combine to form compounds. Figure 2.4 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Chemical Reactions Atoms are joined by chemical bonds (ionic or covalent) A chemical reaction forms and/or breaks chemical bonds Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Electrons and Bonding Electrons occupy energy levels Each level has distinct properties The number of electrons has an upper limit Levels closest to the nucleus fill first Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Electrons and Bonding Bonding involves electrons in the outer level (the valence shell) The ROW on the periodic chart indicates the valence level Full valence shells do not form bonds Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Bonding leads to stability Atoms are stable when the outermost level is complete How to fill the energy levels Level 1: maximum of 2 electrons Level 2: maximum of 8 electrons Level 3: maximum of 18 electrons The valence shell can hold a maximum of 8 electrons The COLUMN on the periodic chart indicates the number of valence electrons in an atom Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Atoms will gain, lose, or share electrons to complete their valence shells and reach a stable state Octet Rule – the Rule of eights Atoms are considered stable when their valence shell has 8 electrons (Except for level 1, Hydrogen: use the duet rule) Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Inert Elements Figure 2.5a Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Reactive Elements Valence shells are not full and are unstable Tend to gain, lose, or share electrons These elements form chemical bonds! Figure 2.5b Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Chemical Bonds Ionic bonds Form when electrons are transferred from one atom to another Ions Charged particles—protons don’t equal electrons Cations are positive (have lost e-) Anions are negative (have gained e-) Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Chemical Bonds Ionic bonds Form when electrons are transferred from one atom to another Ions Charged particles—protons don’t equal electrons Cations are positive (have lost e-) Anions are negative (have gained e-) Metals lose electrons Nonmetals gain (or share) electrons Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Identifying Name Ions Symbol Atomic Number Atomic Mass Number #p #n (most likely) Iodide ion Na+ 9 12 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings # e- Identifying Ions Name Atomic Number Atomic Mass Number I- 53 127 53 74 54 Sodium ion Na+ 11 23 11 12 10 Fluoride F- 9 19 9 10 10 Mg+2 12 24 12 12 10 Iodide Symbol #p #n # e- (most likely) ion ion Magnesium ion Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Ionic Bonds Na Cl Sodium atom (Na) (11p+; 12n0; 11e–) Chlorine atom (Cl) (17p+; 18n0; 17e–) Figure 2.6, step 1 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Ionic Bonds Na Cl Sodium atom (Na) (11p+; 12n0; 11e–) Chlorine atom (Cl) (17p+; 18n0; 17e–) Figure 2.6, step 2 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Ionic Bonds Na Cl Sodium atom (Na) (11p+; 12n0; 11e–) Chlorine atom (Cl) (17p+; 18n0; 17e–) + – Na Cl Sodium ion (Na+) Chloride ion (Cl–) Sodium chloride (NaCl) Figure 2.6, step 3 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Chemical Bonds Covalent bonds Atoms become stable through shared electrons Single covalent bonds share one pair of electrons Double covalent bonds share two pairs of electrons Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Examples of Covalent Bonds Figure 2.7a Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Examples of Covalent Bonds Figure 2.7b Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Examples of Covalent Bonds Figure 2.7c Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Valence Rules In general: Carbon makes 4 bonds Hydrogen makes 1 bond Oxygen makes 2 bonds Nitrogen makes 3 bonds Figure 2.7c Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Polarity —the most important chemical property Figure 2.8 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Polarity —the most important chemical property Some molecules are non-polar Some are polar Have a positive and negative side Figure 2.8 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings What bonds are polar? Look for: O-H C-O or N-H… …bonds in a molecule Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Attraction between molecules Polarity provides attraction between molecules Weak chemical bonds Hydrogen bonds-- Hydrogen is attracted to the negative portion of polar molecule Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Hydrogen Bonds Causes surface tension in water Figure 2.9 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Chemical Reactions Reactants form products Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Chemical Reactions Reactants form products A + B C + D Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Chemical Reactions Reactants form products A + B C + D Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Chemical Reactions Reactants form products A + B C + D Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Patterns of Chemical Reactions Synthesis reaction (A + BAB) Atoms or molecules combine Energy is absorbed Decomposition reaction (ABA + B) Molecule is broken down Chemical energy is released Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Synthesis and Decomposition Reactions Figure 2.10a Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Synthesis and Decomposition Reactions Figure 2.10a Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Synthesis and Decomposition Reactions Figure 2.10b Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Synthesis and Decomposition Reactions Figure 2.10b Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Patterns of Chemical Reactions Exchange reaction (AB + CAC + B) Involves both synthesis and decomposition reactions Switch is made between molecule parts and different molecules are made Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Patterns of Chemical Reactions Figure 2.10c Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Patterns of Chemical Reactions Figure 2.10c Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings