Atoms, Molecules, and Life
<ul><li>Covalent bond  — electrons shared </li></ul><ul><ul><li>Shared unequally —  polar </li></ul></ul><ul><ul><li>Share...
Bonding Involves Electrons <ul><li>One pair electrons per bond </li></ul><ul><li>Outer electrons form bonds </li></ul><ul>...
Most Elements Molecular (a) In hydrogen gas, one electron from each hydrogen atom is shared, forming a single covalent bon...
Ionic Bonding in NaCl Sodium ion #e=#p-1 Chlorine ion #e=#p+1 Negative charge Positive charge ± + – ± + ± + ± + ± + ± + ± ...
Ionic Bonding in NaCl <ul><li>Opposites attract. </li></ul><ul><li>Sodiums nestle between chlorines. </li></ul><ul><li>Per...
Water Is Covalent <ul><li>Electron pair forms covalent bond </li></ul>Each spends some time w/one, then the other atom Les...
Water Molecule H 2 O Oxygen Hydrogens H H O
Polar vs. Nonpolar Bonds <ul><li>Distribution of charge on molecule </li></ul><ul><li>Polar — charged surface </li></ul><u...
Bonding Patterns of Common Atoms       Sulfur Phosphorus Oxygen Nitrogen Carbon Hydrogen
Free Radicals <ul><li>Some cellular reactions produce free radicals </li></ul><ul><ul><li>Free radical : a molecule whose ...
Free Radicals <ul><li>Free radicals are involved in causing heart disease, Alzheimer’s, cancer, and aging </li></ul><ul><l...
Hydrogen Bonds O O H H H H + + + – – + + Hydrogen Bonds Water molecules carry slight charges Electrons favor  O  over  H H...
Hydrogen Bonds Hydrogen bonds are like two children holding very-slippery hands. The bonds constantly break and reform
NaCl Dissolved by Water NaCl is ionicly bonded Water is polar and charged O sticks to Na + H sticks to Cl -
Dissociation + Water Hydroxide ion Hydrogen ion A few water molecules naturally  dissociate <ul><li>Hydroxide ion  is nega...
Cohesion among Water Molecules
The pH Scale Neutral pH +  = pOH – Increasingly Acidic pH +  > pOH – Increasingly Basic pH +  < pOH – 0 -1 -2 -3 -4 -5 -6 ...
Water Stabilizes Temperature <ul><li>Very low or very high temperatures may damage enzymes or slow down important chemical...
Water Stabilizes Temperature <ul><li>Water requires a lot of energy to turn from liquid into a gas ( heat of vaporization ...
 
Water Stabilizes Temperature <ul><li>Water requires a lot of energy to be withdrawn in order to freeze ( heat of fusion ) ...
Water molecules spread apart slightly during the freezing process
 
Water Forms an Unusual Solid <ul><li>Ice floats in liquid water </li></ul><ul><li>Ponds and lakes freeze from the top down...
The End
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Ap Bio Ch2 PowerPoint

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Atoms, Molecules, and Life

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  • Ap Bio Ch2 PowerPoint

    1. 1. Atoms, Molecules, and Life
    2. 2. <ul><li>Covalent bond — electrons shared </li></ul><ul><ul><li>Shared unequally — polar </li></ul></ul><ul><ul><li>Shared equally — nonpolar </li></ul></ul><ul><li>Ionic bond — electron transfers total # </li></ul><ul><ul><li>Both atoms ionized </li></ul></ul><ul><ul><li>May dissociate in water </li></ul></ul>Chemical Bonding
    3. 3. Bonding Involves Electrons <ul><li>One pair electrons per bond </li></ul><ul><li>Outer electrons form bonds </li></ul><ul><li>Behave using “ octet rule ” </li></ul><ul><li>If nearly eight in outer shell </li></ul><ul><ul><li>Desires more electrons </li></ul></ul><ul><ul><li>Oxidizer </li></ul></ul><ul><li>If less than four in outer shell </li></ul><ul><ul><li>Desires fewer electrons </li></ul></ul><ul><ul><li>Reducer </li></ul></ul>
    4. 4. Most Elements Molecular (a) In hydrogen gas, one electron from each hydrogen atom is shared, forming a single covalent bond. The resulting molecule of hydrogen gas is represented as H–H or H 2 . (b) In oxygen gas, two oxygen atoms share four electrons, forming a double bond (O=O or O 2 ).
    5. 5. Ionic Bonding in NaCl Sodium ion #e=#p-1 Chlorine ion #e=#p+1 Negative charge Positive charge ± + – ± + ± + ± + ± + ± + ± + ± + – – – – – – ± + – – – ± + – ± + ± + ± + ± + ± + ± + ± + – – – – – – ± + – – – – – – – – – – ± + – ± + ± + ± + ± + ± + ± + ± + – – – – – – ± + – – – – Sodium #e=2+8+1=#p ± + – ± + ± + ± + ± + ± + ± + ± + – – – – – – ± + – – – – – – – – – – Chlorine #e=2+8+7=#p – – – Electron Completely Transferred
    6. 6. Ionic Bonding in NaCl <ul><li>Opposites attract. </li></ul><ul><li>Sodiums nestle between chlorines. </li></ul><ul><li>Perfectly cubical crystals. </li></ul>Cl - Cl - Cl - Cl - Cl - Cl - Cl - Cl - Cl - Cl - Cl - Cl - Cl - Cl - Cl - Cl - Na + Na + Na + Na + Na + Na + Na + Na + Na + Na + Na + Na + Na + Na + Na + Na + Cl - Cl - Cl - Cl - Cl - Cl - Cl - Cl - Cl - Cl - Cl - Cl - Cl - Cl - Cl - Cl - Na + Na + Na + Na + Na + Na + Na + Na + Na + Na + Na + Na + Na + Na + Na + Na +
    7. 7. Water Is Covalent <ul><li>Electron pair forms covalent bond </li></ul>Each spends some time w/one, then the other atom Less time w/H, more time w/O Causes polarity of H 2 O molecule
    8. 8. Water Molecule H 2 O Oxygen Hydrogens H H O
    9. 9. Polar vs. Nonpolar Bonds <ul><li>Distribution of charge on molecule </li></ul><ul><li>Polar — charged surface </li></ul><ul><ul><li>Prefer other charged molecules </li></ul></ul><ul><ul><li>Soluble in water </li></ul></ul><ul><li>Nonpolar — no residual charge </li></ul><ul><ul><li>Prefer uncharged molecules </li></ul></ul><ul><ul><li>Soluble in oils </li></ul></ul>
    10. 10. Bonding Patterns of Common Atoms       Sulfur Phosphorus Oxygen Nitrogen Carbon Hydrogen
    11. 11. Free Radicals <ul><li>Some cellular reactions produce free radicals </li></ul><ul><ul><li>Free radical : a molecule whose atoms have one or more unpaired electrons in their outer shells </li></ul></ul><ul><li>Free radicals are highly unstable and reactive </li></ul><ul><ul><li>Free radicals steal electrons, destroying other molecules </li></ul></ul><ul><ul><li>Cell death can occur from free radical attack </li></ul></ul>
    12. 12. Free Radicals <ul><li>Free radicals are involved in causing heart disease, Alzheimer’s, cancer, and aging </li></ul><ul><li>Antioxidants like vitamins C and E render free radicals harmless </li></ul>
    13. 13. Hydrogen Bonds O O H H H H + + + – – + + Hydrogen Bonds Water molecules carry slight charges Electrons favor O over H Hydrogen bonds form between O of one and H of another Not a “REAL” bond!!! No transfer of electrons!
    14. 14. Hydrogen Bonds Hydrogen bonds are like two children holding very-slippery hands. The bonds constantly break and reform
    15. 15. NaCl Dissolved by Water NaCl is ionicly bonded Water is polar and charged O sticks to Na + H sticks to Cl -
    16. 16. Dissociation + Water Hydroxide ion Hydrogen ion A few water molecules naturally dissociate <ul><li>Hydroxide ion is negative and basic </li></ul><ul><li>Hydrogen ion is positive and acidic </li></ul>Makes water a good solvent H 2 O Glucose H 2 O H 2 O H 2 O H 2 O – + Hydrogen Bond
    17. 17. Cohesion among Water Molecules
    18. 18. The pH Scale Neutral pH + = pOH – Increasingly Acidic pH + > pOH – Increasingly Basic pH + < pOH – 0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 -11 -12 -13 -14 Lemon Juice Lime Juice Stomach Acid Coffee Urine Water Blood Sea Water Baking Soda Bleach Ammonia Oven Cleaner
    19. 19. Water Stabilizes Temperature <ul><li>Very low or very high temperatures may damage enzymes or slow down important chemical reactions </li></ul><ul><li>Water moderates the effect of temperature change </li></ul><ul><ul><li>Temperature reflects the speed of molecular motion </li></ul></ul><ul><ul><li>It requires 1 calorie of energy to raise the temperature of 1g of water 1 o C (the specific heat of water), so it heats up very slowly </li></ul></ul>
    20. 20. Water Stabilizes Temperature <ul><li>Water requires a lot of energy to turn from liquid into a gas ( heat of vaporization ) </li></ul><ul><ul><li>Evaporating water uses up heat from its surroundings, cooling the nearby environment (as occurs during sweating) </li></ul></ul><ul><ul><li>Because the human body is mostly water, a sunbather can absorb a lot of heat energy without sending her/his body temperature soaring </li></ul></ul>
    21. 22. Water Stabilizes Temperature <ul><li>Water requires a lot of energy to be withdrawn in order to freeze ( heat of fusion ) </li></ul><ul><li>Water freezes more slowly than other liquids </li></ul><ul><li>Most substances become denser when they solidify from a liquid </li></ul><ul><li>Ice is unusual because it is less dense than liquid water </li></ul>
    22. 23. Water molecules spread apart slightly during the freezing process
    23. 25. Water Forms an Unusual Solid <ul><li>Ice floats in liquid water </li></ul><ul><li>Ponds and lakes freeze from the top down and never freeze completely to the bottom </li></ul><ul><ul><li>Many plants and fish therefore are not frozen </li></ul></ul>
    24. 26. The End

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