CHAPTER 2  CHEMISTRY 2-1  Composition of Matter Objectives:1) Describe the structure of an atom 2) Identify the differences between atoms, elements, ions, compounds and molecules 3) Distinguish between covalent and ionic bonds, and explain how both form I. Elements A. Intro 1. What is it? a. A substance that can’t be broken down into simpler chemical substances 2. Example  Gold a. No matter what you do it will always be gold 1. Burn it, crush it into powder, treat it with chemicals, etc.

B. Natural elements in living things 1. Out of 90 naturally occurring elements, only 25 are essential to living organisms C. Each element is identified with a 1 or 2 letter symbol 1. Carbon-C, Oxygen-O, Calcium-Ca

II. Atoms: The building blocks of elements A. Atom 1. The smallest particle of an element that has the characteristics of that element B. The structure of an atom 1. Nucleus a. The center of the atom b. Composed of protons & neutrons 1. Protons  + charged particles 2. Neutrons  neutral, no charge

2. Electron cloud a. The space around the atom’s nucleus that is occupied by fast moving electrons 1. Electrons  - charged particles b. Because electrons move so fast around the nucleus they appear as a cloud

3. Electron energy level a. Regions or orbits around the nucleus in which electrons travel b. Each energy level has a limited capacity for electrons The first energy level a. The smallest b. Can hold a maximum of 2 electrons 2. The second energy level a. Can hold a maximum of 8 electrons 3. The third energy level a. Can hold a maximum of 18 electrons

Atomic Number and Atomic Weight Atomic Number number of protons in the nucleus of one atom each element has a unique atomic number equals the number of electrons in the atom Atomic Weight the number of protons plus the number of neutrons in one atom electrons do not contribute to the weight of the atom 2-5

c. Electrons will always fill the first energy level first then move to the next 1. Oxygen=8 electrons a. 2 electrons in 1 st energy level b. 6 electrons in 2 nd energy level 4. Atoms have no net charge a. They contain equal number of electrons & protons

III. Compounds & Bonding A. Intro 1. What is a compound? a. A substance that is composed of 2 or more different elements that are chemically combined b. Water  H2O 1. 2 hydrogen atoms combined with 1 oxygen atom 2. Why do atoms bond/combine? a. To become more stable

1. An atom becomes more stable when its outermost energy level is full a. Oxygen 1. Only has 6 electrons in outermost shell, it wants 2 more 2. It gets 2 more by sharing them with hydrogen  H2O

B. How covalent bonds form 1. What is a covalent bond? a. The force that holds 2 atoms together when the share electrons 2. Most compounds in organisms have covalent bonds 3. Molecules a. A group of atoms held together by covalent bonds

C. How ionic bonds form 1. What is an ion? a. An atom that has lost or gained an electron 1. It now will have a charge b. A charged particle 2. Ionic bonding a. The attractive force between 2 ions of opposite charge b. Example  Sodium Chloride (NaCl) 1. Na-11 electrons Cl-17 electrons (1 in outer level) (7 in outer level) 2. Na needs to loose 1 electron Cl needs to gain 1 electron 3. Na gives 1 electron to Cl making Na happy and Cl happy a. However, Na now has a positive charge and Cl now has a negative charge b. The difference in charge is what attracts them to each other creating an ionic bond

2-2  Energy Objectives:1) Describe how energy changes are involved in chemical reactions 2) Explain how enzymes affect chemical reactions in organisms I. Energy and chemical reactions A. Chemical Reactions 1. Living things go through thousands of chemical reactions in order to maintain homeostasis 2. Chemical equations a. Reactants on the left & Products on the right 1. Reactants a. Compound or atom that is involved in a chemical reaction 2. Products a. A compound formed by a chemical reaction

B. Energy transfer 1. In every chemical reaction energy is either released or absorbed a. Where is this energy released from or absorbed by? 2. Endergonic/Endothermic reactions a. A reaction in which energy is absorbed in order to create the products 1. If energy is absorbed (removed from the environment) during the reaction what will the temperature “feel” like? 3. Exergonic/Exothermic reactions a. A reaction in which energy is released in order to create the products 1. If energy is released (put into the environment) during the reaction what will the temperature “feel” like? 4. Example a. Using muscles to exercise 1. When your muscles work they break down glucose (a sugar) to get energy

I. A Solution A. A mixture in which one or more substances (solutes) are distributed evenly in another substance (solvent) 1. Solute a. The substance that is being dissolved 1. Solvent a. The substance that is doing the dissolving II. The importance of solutions A. Many essential substance needed by living organisms are dissolved in water 1. Sugars, salts, ions 2. Can be good or bad depending on [ ] 2-3  Solutions Objectives:1) Define solution, solute, solvent, and concentration. 2) Contrast the properties of acids and bases 3) Describe the use of the pH scale

B. The more solute dissolved in a solvent the greater the [ ] (strength) 1. Organisms can’t live unless the [ ] is within a specific range a. For example--> What results if the [ ] of sugar in your blood (mostly water) is not right? 1. Diabetes III. Acids & Basis A. Acids 1. A solution that contains a large number of Hydronium ions (H + ) 2. Very corrosive 3. Typically has a sour taste B. Basis 1. A solution that contains a small amount of H + (high amount of hydroxide ions (OH - )) 2. Can by corrosive 3. Typically have a bitter taste C. pH scale 1. A scale used to measure the amount of H + in a particular solution 2. Ranges from 0-14 a. 0-6 = acidic solution b. 7 = neutral solution c = basic solution

Why is all of this (chemistry) important? I. The body needs to maintain a proper, balanced internal environment in order to function. A. Called homeostasis 1. chemistry helps the cells of the body to maintain homeostasis a. Bonding, solutions, pH, etc