Figure 2.8 A ball bouncing down a flight of stairs provides an analogy for energy levels of electrons. Third shell (highest energy level in this model) Second shell (higher energy level) First shell (lowest energy level) Atomic nucleus Energy absorbed Energy lost (b) (a)
Figure 2.9 First shell Second shell Third shell Hydrogen 1 H Lithium 3 Li Sodium 11 Na Beryllium 4 Be Magnesium 12 Mg Boron 5 B Aluminum 13 Al Carbon 6 C Silicon 14 Si Nitrogen 7 N Phosphorus 15 P Oxygen 8 O Sulfur 16 S Fluorine 9 F Chlorine 17 Cl Neon 10 Ne Argon 18 Ar Helium 2 He 2 He 4.00 Mass number Atomic number Element symbol Electron distribution diagram
Figure 2.12 (a) Hydrogen (H 2 ) (b) Oxygen (O 2 ) (c) Water (H 2 O) Name and Molecular Formula Electron Distribution Diagram Lewis Dot Structure and Structural Formula Space- Filling Model (d) Methane (CH 4 )
Figure 2.18 Natural endorphin Morphine Carbon Hydrogen Nitrogen Sulfur Oxygen (a) Structures of endorphin and morphine (b) Binding to endorphin receptors Brain cell Morphine Natural endorphin Endorphin receptors
Molecular Mimicry Morphine, heroine, and other opiates mimic endorphins by binding to endorphin receptors in the brain affecting both pain perception & emotional state –It turn out that molecules with similar shapes, structural homology, have similar effects
Figure 2.UN08 Female silkworm moths (Bombyx mori) attract males by emitting chemical signals that spread through the air. A male hundereads of meters away can detect these molecules and fly towards their source. The sensory organs responsible for this behavior are the comb like antennae visible in the photograph. Each filament of an antenna is equipped with thousands of receptor cells that detect the sex attractant. Based on what you learned, propose a hypothesis to account for the ability of the male moth to detect specific molecules in the air. What predictions does you hypothesis make? Design an experimen to test one of these predictons.