Chemistry Review CHAPTER 2 IN TEXT

Transcription

1 Chemistry Review CHAPTER 2 IN TEXT

2 Chemistry of Life Living organisms and the world they live in are subject to the basic laws of physics and chemistry. Life can be organized into a hierarchy of structural levels. Atoms are organized into molecules, and molecules are organized into cells. Somewhere in the transition from molecules to cells, we cross the boundary between nonlife and life. At each successive level, additional emergent properties appear Scale of the Universe

3 Emergent Properties of Systems Has properties and functions NOT present in the individual components. Whole (system) is greater than the sum of the parts. CANNOT predict properties of system from properties of parts This is called Synergy There is nothing in the chemistry of a toenail that predicts the existence of a human being. Buckminster Fuller

4 Synergy in Salt Ordinary Table Salt (NaCl, Sodium Chloride) Na (sodium) is a metal, highly reactive in water, explosive, burns with a yellow flame. Cl (chlorine) is a deadly greenish gas. Both are poisonous and deadly BUT...

5 SALT When combined, produce something that we cannot live without. Something unique and new and unpredictable happens when two or more things come together and work together

6 Biological Hierarchy New properties emerge at each level in the biological hierarchy. Each level of biological organization has emergent properties. Biological organization is based on a hierarchy of structural levels, each building on the levels below. Synergy!

7 Organisms are Composed of Matter Matter is made up of elements. About 25 of the 92 naturally occurring elements are known to be essential for life. Four elements carbon (C), oxygen (O), hydrogen (H), and nitrogen (N) make up 96% of living matter. Most of the remaining 4% of an organism s weight consists of phosphorus (P), sulfur (S), calcium (Ca), and potassium (K). Trace elements are required by an organism but only in minute quantities. Some trace elements, like iron (Fe), are required by all organisms. Other trace elements are required by only some species.

8 What do we Remember? Protons Neutrons Electrons Mass Charge Location

9 An elements properties depend on the structure of its atoms Subatomic particles: proton, neutron, electron Atomic number - number of protons Mass number -the sum of the number of protons and the number of neutrons in the nucleus of an atom. Electron configuration and chemical properties Valence electrons

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11 Valence Electrons

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13 The Energy Levels of Electrons An atom s electrons Vary in the amount of energy they possess They have energy levels If an atom absorbs energy, then the electrons will be bumped up to a higher energy level

14 Energy Energy Is defined as the capacity to cause change Potential energy Is the energy that matter possesses because of its location or structure Types?

15 Energy Levels Energy levels Are represented by electron shells Third energy level (shell) Second energy level (shell) Energy absorbed First energy level (shell) Atomic nucleus Energy lost Figure 2.7B (b) An electron can move from one level to another only if the energy it gains or loses is exactly equal to the difference in energy between the two levels. Arrows indicate some of the step-wise changes in potential energy that are possible.

16 Chemical Bonds Covalent- two atoms share a pair of valence electrons The attraction of an atom for the shared electrons of a covalent bond is called its electronegativity. Ionic - two atoms are so unequal in their attraction for valence electrons that one atom strips an electron completely from the other. stealing electrons

17 Covalent Bonds Covalent Bond: Electrons are shared when the atoms share: two electrons è single bond four electrons è double bond six electrons è triple bond

18 Covalent Bond Example: H 2 O

19 Ionic Bonds All atoms want 8 valence electrons They can gain or lose electrons to get 8 Ionic bond: electrons are transferred gain electron: negative charge Anion lose electron: positive charge Cation Ions: charged atoms

20 Ionic Bond Example: NaCl

21 Types of Bonds

22 Hydrogen Bonds Weak bonds that form when the partial positive charge of a hydrogen atom in a polar covalent bond is attracted to the partial negative charge on another polar covalently bonded atom. d d + Figure 2.15 Water (H 2 O) Ammonia (NH 3 ) H O H d + d N H H d+ H d+ d + A hydrogen bond results from the attraction between the partial positive charge on the hydrogen atom of water and the partial negative charge on the nitrogen atom of ammonia.

23 Hydrogen Ion = Proton A Note on Hydrogen

24 Molecular shape & function Molecular shape determines how biological molecules recognize and respond to one another with specificity

25 Natural endorphin Carbon Nitrogen Hydrogen Sulfur Oxygen Morphine (a) Structures of endorphin and morphine. The boxed portion of the endorphin molecule (left) binds to receptor molecules on target cells in the brain. The boxed portion of the morphine molecule is a close match. Natural endorphin Morphine Figure 2.17 Brain cell Endorphin receptors (b) Binding to endorphin receptors. Endorphin receptors on the surface of a brain cell recognize and can bind to both endorphin and morphine.

26 Chemical Reactions Reactants products Most reactions are reversible leading to chemical equilibrium The rate of formation of products is the same as the rate of breakdown of products (formation of reactants), and the system is at chemical equilibrium. At equilibrium, the concentrations of reactants and products are typically not equal, but their concentrations have stabilized at a particular ratio.