The Chemical Context of Life

The Chemical Context of Life 0 2 Lecture Presentation by Nicole Tunbridge and Kathleen Fitzpatrick

Figure 2.2 What elements form this compound? Explain how table salt has emergent properties. Sodium Chlorine Sodium chloride

Table 2.1 Highlight the four elements that make up 96% of all living matter. Trace elements are listed at the bottom of the table. How are they different from essential elements?

Figure 2.3 Explain how natural selection might have played a role in the evolution of species that are tolerant of serpentine soils.

Figure 2.4 Label the electrons, neutrons, protons, nucleus, and electron shell. What is its atomic number and mass? Compare and contrast these models. - - + + + + (a) (b)

Figure 2.5 Explain the use of isotopes in this medical application. Cancerousthroattissue

Figure 2.6 Electrons have potential energy. Explain why energy must be absorbed in a fixed amount when an electron moves farther away from the nucleus and lost when an electron moves towards the nucleus. (a) A ball bouncing down a flightof stairs provides an analogyfor energy levels of electrons. Third shell (highest energylevel in this model) Energyabsorbed Second shell (next highestenergy level) First shell (lowest energylevel) Energylost Atomicnucleus (b)

Figure 2.7 Which electrons are directly involved in chemical reactions between atoms? How many does lithium have? Lithium would most likely react with atoms of which column and why? Atomic number Helium 2He 2 Hydrogen 1H He Atomic mass Element symbol 4.003 Firstshell Electrondistributiondiagram Lithium 3Li Beryllium 4Be Boron 5B Carbon 6C Nitrogen 7N Oxygen 8O Fluorine 9F Neon 10Ne Secondshell Sodium 11Na Magnesium 12Mg Aluminum 13Al Silicon 14Si Phosphorus 15P Sulfur 16S Chlorine 17Cl Argon 18Ar Thirdshell

Figure 2.8 What does an orbital describe and how many electrons can exist in a single orbital? First shell Second shell y x First shell Neon,with twofilled shells(10 electrons) z Second shell 1s orbital 2s orbital Three 2p orbitals (a) Electron distributiondiagram (b) Separate electron orbitals 1s, 2s, and2p orbitals (c) Superimposed electron orbitals

Figure 2.10a Why is this molecule not considered a compound? Why is the bond within this molecule considered a nonpolar covalent bond and not polar? Use the term electronegativity in your explanation. Name andMolecularFormula Electron Distribution Diagram Lewis Dot Structure and Structural Formula Space- Filling Model (a) Hydrogen (H2) H H

Figure 2.10b Why is the bond between the two oxygen atoms considered a double bond? Name andMolecularFormula Electron Distribution Diagram Lewis Dot Structure and Structural Formula Space- Filling Model (b) Oxygen (O2) O O

Figure 2.10c Why are the hydrogen atoms not directly across from one another in the water molecule? (Think about this one!) Name andMolecularFormula Electron Distribution Diagram Lewis Dot Structure and Structural Formula Space- Filling Model (c) Water (H2O) H O H

Figure 2.10d Are the hydrogen-carbon bonds considered polar or nonpolar? Is the molecule considered polar or nonpolar? Explain the apparent contradiction. Name andMolecularFormula Electron Distribution Diagram Lewis Dot Structure and Structural Formula Space- Filling Model (d) Methane (CH4) H H H C H

Animation: Covalent Bonds

Figure 2.11 What is a result of oxygen’s higher electronegativity relative to hydrogen’s in the water molecule? d- O H H d+ d+ H2O

Figure 2.12-2 Compare and contrast covalent bonds and ionic bonds. + - Na Cl Na Cl NaSodium atom Cl Chlorine atom Na+Sodium ion(a cation) Cl-Chloride ion(an anion) Sodium chloride (NaCl)

Animation: Ionic Bonds

Figure 2.13 If molecules are produced from covalent bonds, what are produced from ionic bonds? Na+ Cl-

Figure 2.14 Would it be possible for hydrogen to be partially negative and create a hydrogen bond? Explain your answer. d- d+ Water (H2O) d+ Hydrogen bond d- Ammonia (NH3) d+ d+ d+

Figure 2.UN02 Explain how Van der Waals interactions between the animal’s skin and the surface allow it to defy gravity’s force. List the 4 interactions (Van der Waals, covalent, ionic, hydrogen) in order of increasing strength.

Figure 2.16 If you were a pharmaceutical researcher, why would you want to learn the three dimensional shapes of naturally occurring signaling molecules? Key Nitrogen Carbon Natural endorphin Sulfur Hydrogen Oxygen Morphine (a) Structures of endorphin and morphine Natural endorphin Morphine Endorphin receptors Brain cell (b) Binding to endorphin receptors

Figure 2.UN03 Write out the chemical equation for the formation of ammonia from hydrogen and nitrogen. Label the reactants and products of the reaction. Explain the role of Le Châtlier’s Principle in determining the chemical equilibrium.

Figure 2.17 Write out the chemical equation for photosynthesis. Explain how this photo relates the reactants and products in the equation for photosynthesis.

The Chemical Context of Life