Chapter 2 Matter and Energy

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

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

All matter is composed of atoms 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 CHON

Atomic Structure – Subatomic particles Name Symbol Mass Charge Location Proton Neutron Electron Figure 2.1

Atomic Structure – Subatomic particles Name Symbol Mass Charge Location Proton p 1 amu +1 in nucleus Neutron n 1 amu 0 in nucleus Electron e- 0 amu -1 around nucleus, in electron cloud Figure 2.1

Atomic Structure Figure 2.1

Atomic Structure of Smallest Atoms Electrons have different energy levels. Only the outer level affects an atom’s chemical properties! Figure 2.2

K 19 Atomic number —equal to the number of protons Identifying Elements Atomic number —equal to the number of protons Atomic mass number —sum of the protons and neutrons 19 39.0983 Atomic Number = number of protons K Average atomic mass, in amu/atom Name Symbol Potassium

K 20 17 Identifying Elements Sulfur Name Symbol AtomicNumber Atomic Mass Number # p # n (most likely) # e- Sulfur K 20 17

S 16 32 K 19 39 20 Ca 40 Cl 17 35 18 Identifying Elements Sulfur Name Symbol AtomicNumber Atomic Mass Number # p # n (most likely) # e- Sulfur S 16 32 Potassium K 19 39 20 Calcium Ca 40 Chlorine Cl 17 35 18

Isotopes and Mass Number Have the same number of protons Vary in number of neutrons Figure 2.3

Isotopes and Mass Number Chlorine has two common isotopes, Cl-35 and Cl-37 Figure 2.3

Isotopes and Mass Number Chlorine has two common isotopes, Cl-35 and Cl-37 How many neutrons in each? Figure 2.3

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

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

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

Isotopes and 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

Isotopes and Average Atomic Mass The periodic table is arranged by atomic number. The average atomic mass usually increases with atomic number.

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.

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?

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?

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

Compounds Elements combine to form compounds. Figure 2.4

Chemical Reactions Atoms are joined by chemical bonds (ionic or covalent) A chemical reaction forms and/or breaks chemical bonds

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

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

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

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)

Inert Elements Figure 2.5a

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

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-)

Nonmetals gain (or share) electrons 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

Na+ 9 12 Identifying Ions Iodide ion Name Symbol AtomicNumber Atomic Mass Number # p # n (most likely) # e- Iodide ion Na+ 9 12

I- 53 127 74 54 Na+ 11 23 12 10 F- 9 19 Mg+2 24 Identifying Ions Name Symbol AtomicNumber Atomic Mass Number # p # n (most likely) # e- Iodide ion I- 53 127 74 54 Sodium ion Na+ 11 23 12 10 Fluoride F- 9 19 Magnesium ion Mg+2 24

Ionic Bonds Na Cl Sodium atom (Na) (11p+; 12n0; 11e–) Chlorine atom (Cl) (17p+; 18n0; 17e–) Figure 2.6, step 1

Ionic Bonds Na Cl Sodium atom (Na) (11p+; 12n0; 11e–) Chlorine atom (Cl) (17p+; 18n0; 17e–) Figure 2.6, step 2

+ – Ionic Bonds Na Cl Na Cl Sodium atom (Na) (11p+; 12n0; 11e–) Chlorine atom (Cl) (17p+; 18n0; 17e–) Sodium ion (Na+) Chloride ion (Cl–) Sodium chloride (NaCl) Figure 2.6, step 3

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

Examples of Covalent Bonds Figure 2.7a

Examples of Covalent Bonds Figure 2.7b

Examples of Covalent Bonds Figure 2.7c

Valence Rules In general: Carbon makes 4 bonds Hydrogen makes 1 bond Oxygen makes 2 bonds Nitrogen makes 3 bonds Figure 2.7c

Polarity —the most important chemical property Figure 2.8

Polarity —the most important chemical property Some molecules are non-polar Some are polar Have a positive and negative side Figure 2.8

What bonds are polar? Look for: O-H C-O or N-H… …bonds in a molecule

Attraction between molecules Polarity provides attraction between molecules Weak chemical bonds Hydrogen bonds-- Hydrogen is attracted to the negative portion of polar molecule

Hydrogen Bonds Causes surface tension in water Figure 2.9

Reactants form products Chemical Reactions Reactants form products

Reactants form products Chemical Reactions Reactants form products A + B  C + D

Reactants form products Chemical Reactions Reactants form products A + B  C + D

Reactants form products Chemical Reactions Reactants form products A + B  C + D

Patterns of Chemical Reactions Synthesis reaction (A + BAB) Atoms or molecules combine Energy is absorbed Decomposition reaction (ABA + B) Molecule is broken down Chemical energy is released

Synthesis and Decomposition Reactions Figure 2.10a

Synthesis and Decomposition Reactions Figure 2.10a

Synthesis and Decomposition Reactions Figure 2.10b

Synthesis and Decomposition Reactions Figure 2.10b

Patterns of Chemical Reactions Exchange reaction (AB + CAC + B) Involves both synthesis and decomposition reactions Switch is made between molecule parts and different molecules are made

Patterns of Chemical Reactions Figure 2.10c

Patterns of Chemical Reactions Figure 2.10c