Chemistry of Life

What’s the Matter? All of the materials around you are made up of matter. You are made up of matter, as are the chair you sit on and the air you breathe. 1. Give an example of solid matter. 2. Give an example of liquid matter. 3. Give an example of gaseous matter. 4. Is all matter visible? 5. Does all matter take up space?

Matter & Mass Matter: Anything that has mass and takes up space up space Mass: Measure of the amount of matter an object contains object contains

The Nature of Matter Atoms Smallest part of an element From Greek work atomos = Unable to be cut or indivisible

Made up of 3 parts  Protons (+) charge  nucleus  Electrons (-) charge  electron cloud  Neutron (no charge)  nucleus

Element Pure substance, contains only 1 type of atom More than 100, but only about 2 dozen are found in living things. 4 elements that make up 96% of living matter H (hydrogen), O (Oxygen), N (Nitrogen), C (Carbon) 6 most common - CHNOPS

Atomic # Atomic # Atomic Symbol Atomic Symbol Element Name Element Name Atomic Mass Atomic Mass

Atomic Number Number of protons and or electrons Atomic # = p + = e - Atomic Mass or Mass Number Number of protons + number of neutrons p + + n = mass number n= mass number – p+

Practice 1. What is the atomic # of Carbon? 2. How many electrons does Boron have? 3. What is the mass number of Neon? 4. How many protons does Helium have? 5. How many neutrons does Chlorine have?

Isotopes An element with the same number of protons but different number of neutrons

Isotopes

Isotopes of Carbon Nonradioactive carbon-12 Radioactive carbon-14 Nonradioactive carbon-13 6 electrons 6 protons 6 neutrons 6 electrons 6 protons 7 neutrons 6 electrons 6 protons 8 neutrons

Radioactive Isotopes  Unstable nucleus  Break down at a constant rate  Used to date rocks & fossils  Used as a cancer treatment  Used to kill bacteria  Used as “tracers” follow movement of substances in an organism

PET (positron emission tomography) SCANS

Other scans using radioactive tracers A hepatobiliary (HIDA) scan is an imaging procedure used to diagnose problems in the liver, gallbladder and bile ducts. 1RnYE 1RnYE

Chemical Compounds Compound Chemical combination of 2 or more different elements Composition of compound is shown by molecular formula Ex] H 2 O Physical & chemical properties of a compound are very different than those of the elements that make it up EX] NaCl

Chemical Bonds  Atoms in compounds are held together by chemical bonds  Bonds involve electrons in outer energy level  Outer most energy level is known as the valence shell 1 st  2 electrons 2 nd  8 electrons 3 rd  18 electrons  Valence shell holds a maximum of 8 electrons

1) Covalent Bonds Elements share electrons for stability. Number of bonds? Use “HONC-1234” Quite strong… takes a lot of energy to break them! –But you CAN, because we burn fat, recycle materials… plants break bonds in CO2 and H20 to rework them into complex sugars Ex: H 2 O, CO 2, C 6 H 12 O 6 (glucose) –Some polar, some non polar…. 

Covalent Bond

Molecular structures of covalent compounds Glucose Hemoglobin DNA

(polar covalent?) Oxygen is more greedy for electrons than hydrogen, so it has more ‘custody’ Creates partially negative and positive areas

2) Ionic Bonds involve the transfer of electrons. Whether they donate or receive is determined by the number of electrons in the valence shell. –C–C–C–Cation: positive (b/c it lost e-) –A–A–A–Anion: negative (b/c it stole e-) –D–D–D–Due to extreme differences in electronegativity Ex: NaCl (table salt) or KI (a stain) or CaCO3 (in seashells) These molecules dissolve easily in water, blood, cytoplasm, tree sap… etc.

Sodium atom (Na)Chlorine atom (Cl)Sodium ion (Na + )Chloride ion (Cl - ) Transfer of electron Protons +11 Electrons -11 Charge 0 Protons +17 Electrons -17 Charge 0 Protons +11 Electrons -10 Charge +1 Protons +17 Electrons -18 Charge -1 Figure 2-3 Ionic Bonding

Like & Unlike charges

3) Hydrogen bonds Usually between water molecules (makes them cohesive) Causes: –Ice’s low density –Sweat’s cooling power –Plants drinking ‘against gravity’ –Insects to walk on water

IceCohesion Sweat 3) Hydrogen bonds

Relative Bond Strengths

Chemistry Summary Everything around you is made of matter composed of atoms Atoms - nucleus of protons and neutrons surrounded by a cloud of electrons. Elements have different # p+, e-, and n0 Isotopes have the same # p+ but diff # n0

Chemistry Summary Compounds have 2 or more elements Bonds form from interaction of outer e- Covalent bonds- strongest - share e- Ionic bonds – medium – trade e- –Water soluble Hydrogen bonds – weak – interaction b/w polar molecules