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Understanding the Chemistry of Life: Elements, Compounds, and Bonds

Explore the foundational concepts in the chemistry of life, including elements, compounds, atoms, molecules, and chemical bonds. Understand how these fundamental components dictate the behaviors and interactions within living organisms.

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Understanding the Chemistry of Life: Elements, Compounds, and Bonds

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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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