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Unit 1 The Chemistry of Life

Unit 1 The Chemistry of Life. Chapters 2-5. Chapter 2 The chemical context of life. You must know: The 3 subatomic particles & their significance The types of bonds, how they form, & their relative strengths. 2.1. Matter consists of elements in pure forms

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Unit 1 The Chemistry of Life

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  1. Unit 1The Chemistry of Life Chapters 2-5

  2. Chapter 2 The chemical context of life • You must know: • The 3 subatomic particles & their significance • The types of bonds, how they form, & their relative strengths

  3. 2.1 • Matter consists of elements in pure forms • Matter consists in combinations called compounds

  4. What is matter? • Anything that has mass and takes up space • Living or nonliving • Element • Substance that cannot be broken down to other substances by chemical reactions • Periodic Table

  5. Compound • A substance consisting of two or elements combined in a fixed ratio: • Example: Water H2O or Table Salt NaCl • A compound has characteristics different from those of its elements • Molecule • A molecule is formed when two or more atoms join together chemically • Example: Molecular hydrogen (H2), molecular oxygen (O2) and molecular nitrogen (N2) • *** All compounds are molecules but not all molecules are compounds

  6. C, H, O, N • Make up 96% of living matter • 25 of the 92 Natural elements are essential to life • The rest are trace elements • Example: Fe & I

  7. 2.2 • Properties of an element depend on the structure of its atoms • Atoms • Smallest unit of an element that retains the property of the element • Made up of Protons, Neutrons, & Electrons

  8. Protons • Positively charged • Found in the nucleus • Determine the element

  9. Electrons • Negatively charged • Found in electron shells (or electron cloud) • Determine chemical properties • Determine reactivity of the element

  10. Neutrons • Have no charge • Found in the nucleus • The number can vary in the same element – called ISOTOPES • Example: 12C and 14C are isotopes of Carbon – both have 6 protons, but 12C has 6 neutrons & 14C has 8 neutrons

  11. Atomic number • The number of protons an element has • Unique to every element • Also the number of electrons – why? • Mass number • The sum of its protons & neutrons • How we determine isotopes

  12. 2.3 • Formation and function of molecules depend on chemical bonding • Chemical bond • Interactions between the valence electrons (outermost electrons) of different atoms • Atoms are held together by chemical bonds to form molecules • Two main types of bonds: • Ionic • Covalent

  13. Ionic bonds • 2 atoms attract valence electrons so unequally that the more electronegative atom steals the electron away from the less electronegative atom • An ion is the resulting charged atom or molecule • Cation = positive • Anion = negative • Ionic bonds occur because these ions will be either + or – charged and they are attracted – why? • Example – see board

  14. Covalent bond • When valence electrons are SHARED • Can share 1, 2, or 3 electrons • Nonpolar CB • When the shared electrons are shared equally • Example: O = O or H-H • Polar CB • When there is unequal sharing of electrons • Example: Water – causes the O to be slightly - & the H’s are slightly +

  15. Other bonds: • Hydrogen • Weak bonds that form between the positively charged H atom of one molecule & the strongly (–) O or N of another • Van der Waals interactions • Very weak, transient connections that are results of asymmetrical distribution of electrons within a molecule • Contribute to the 3-D shape of large molecules (ch 5)

  16. 2.4 • Chemical reactions are the making and breaking of chemical bonds • The starting molecules of a chemical reaction are called reactants • The final molecules of a chemical reaction are called products

  17. Some chemical reactions go to completion: all reactants are converted to products • All chemical reactions are reversible: products of the forward reaction become reactants for the reverse reaction • Chemical equilibrium is reached when the forward and reverse reaction rates are equal *** Photosynthesis & Cellular Respiration ***

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