Lab 2 Atomic Level of Organization Laboratory Objectives Describe the subatomic particle of atoms. Identify common atoms from based on their structure. List and describe the three major types of chemical bonds. Describe the fundamental characteristics of each of the three major bond types. Describe the difference between neutral atoms, ions and isotopes. Characterize the nature of molecules that are soluble in water. Define acid, base, and salt. Compare the relationship between acids and bases. Relate the acidity or basic nature of a solution to its ph. Characterize the function of a buffer. 1
Activity 1: Common Atoms Organization > See > Visual Anatomy > Chemical Structures > Illustrated Anatomy > Atomic structures of several stable atoms 1. List the three main subatomic particles, their location, and respective charges. 2. Contrast the electron-shell model with the electron-cloud model. 3. How can a neutrally-charged atom be identified by the number of electrons? 4. Can the number of electrons in the outer shell narrow down the identity of an atom? How? 5. Which of these atoms contains only one electron shell? 2
Activity 2: Chemical Bonding Organization > See > Animation: Chemical Bonding > Sections 1.1, 2.1, 3.1-3.3, 4.1-4.2, and 5.1-5.3 Sections 1.1 and 2.1 1. What are the three main types of chemical bonds? 2. To form bonds, which subatomic particle plays the biggest role? Why? Sections. 3.1-3.4 3. Why are atoms charged after electron transfer? 4. Why are ionic bonds uncommon in the human body? Sections 4.1-4.2 5. Representing covalent bonds, draw the following molecules: O2, H2, and N2. Sections 5.1-5.3 6. How does one atom become partially-positive and one partially-negative? 7. Changes in what conditions can cause hydrogen ions to break? 3
Activity 3 : Bond Boulevard Organization > Do > Interactive Exercise: Bond Boulevard 1. The bonds within a water molecule are polar-covalent bonds. The bonds between water molecules are hydrogen bonds. Explain these statements. 2. List the three main bond types in order of their relative strength. 3. Why would an atom with only four electrons in the outer shell likely not form an ionic bond? 4. Why would an atom with 8 electrons in its outer shell not form ionic, covalent, or hydrogen bonds? 4
Activity 4: Chemical Bonds Organization > Do > Interactive Exercise: Bond Boulevard 1. What is the difference between electron transfer and electron sharing? 2. Which of these two molecules is non-polar? Why? C-C or O-H 5
Activity 5: Solubility Organization > See > Animation: Polarity and Solubility > Sections 1.1-1.2, 2.1, 3.1 1. Are atoms that can form hydrogen bonds soluble or insoluble in water? Why? 2. Why can carbohydrates, proteins, DNA, RNA, and ATP all be easily dissolved? 3. Non-polar molecules in the body contain large amounts of which two atoms? 6
Activity 6: Isotopes An isotope is an atom of a given element with a different number of neutrons. To find the number of neutrons for a given atom, subtract the atomic number from the mass number. For example, the most common isotope of potassium ( 39 K) has 20 neutrons (39 total nucleons - 19 protons). Different isotopes of potassium all have 19 protons, but have varying numbers of neutrons. [Note: On the periodic table,varied masses of isotopes account for the uneven atomic mass, such as 39.10 for potassium] 1. Compare 39 K, 40 K, and 41 K. 2. How does the isotope 14 C differs from 12 C? 3. Oxygen has three common isotopes ( 16 O, 17 O and 18 O). The atomic number of oxygen is 8. The atomic mass of oxygen is 15.999. How many neutrons does the most common isotope of oxygen have? Radioisotopes have a nuclear structure that is unstable and can spontaneously decay, emitting radiation. Each radioactive isotope has its own distinctive half-life, which is the time required for the radioactive isotope to emit half of its original amount of radiation. 1. How can the rate of decay for a substance help identify its age? 2. How can radiation treat cancer? 3. How can radiation cause cancer? 7
Activity 7: Acids and Bases Organization > See > Animation: Acids and Bases > Sections 1.1, 2.1, 3.1, 4.1, 5.1-5.2 Section 1.1 1. Why is an acid referred to as a proton donor? Why is a base a proton acceptor? 2. True or false, the ph scale measures the number of hydrogen atoms in a molecule? Explain? Section 2.1 3. A solution with a ph less than 7.0 is considered. Sections 3.1 and 4.1 4. What is the difference between strong and weak acids? Sections 5.1-5.2 5. How does a buffer protect molecules in the body? 8
Activity 8: Destination: Acid/Base Balance Organization > Do > Interactive Exercise: Destination Acid/Base Balance 1. NaOH (sodium hydroxide) is an example of a(n), that is, a chemical that breaks apart into hydroxide ions (OH - ) (or proton acceptors) and one or more cations. 2. H2SO4 (hydrogen sulfate) is an example of a(n), that is, a chemical that dissociates into hydrogen ions (H + ) (or proton ) and one or more anions. 3. Salts, such as NaCl (sodium chloride), are chemicals that dissolve in water to form cations and ions, neither of which is an or a. 4. Which ph has the highest concentration of OH - ions? 5. A solution with ph = 8 has 10 times (more or less) H + ions than a solution with ph = 7. 6. A solution with ph = 5 has times (more or less) H + ions than a solution with ph = 7. 9