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Chapter 2

Chapter 2. The Chemical Context of Life. Chemistry. Definition Study of matter and its transformations Matter Has mass and occupies space Transformations Chemical reactions Break or form chemical bonds. Units of Matter. Element

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Chapter 2

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  1. Chapter 2 The Chemical Context of Life

  2. Chemistry • Definition • Study of matter and its transformations • Matter • Has mass and occupies space • Transformations • Chemical reactions • Break or form chemical bonds

  3. Units of Matter • Element • Substance that cannot be broken down further by chemical means • Compound • Substance composed of more than one element • Molecule • Substance composed of more than one atom • Includes diatomic elements

  4. Elements found in Living Organisms • 98 % of living mass composed of 4 elements • Oxygen • Carbon • Hydrogen • Nitrogen • Minerals • Trace elements

  5. The AtomBasic Unit of Elements • Most fundamental unit of an element that retains the properties of the element • Structure determines properties of element • Composed of sub atomic particles

  6. Subatomic Particles • Proton • Neutron • Electron

  7. Protons • Composed of quarks • 2 ups and a down • http://en.wikipedia.org/wiki/Quark • Positive charge of +1 • Mass of 1 AMU or Dalton • Resides in atomic nucleus • Confers identity • Atomic number

  8. Neutrons • Composed of quarks • 2 downs and an up • Electrically neutral • Mass of 1 AMU • Resides in atomic nucleus • Stabilizes atomic nucleus • Contributes to atomic mass • Number varies • Isotopes

  9. Quarks and Leptonsboth Fermions

  10. Isotopes • Forms of an element that differ in the number of neutrons • Atomic mass changes but atomic number does not • May be radioactive if atomic nucleus is over crowded

  11. Isotopes

  12. Common Radioactive Isotopes

  13. Types of Radioactive emissions • Alpha • Helium nucleus • 2protons, 2 neutrons • Beta • Electron equivalent • Neutron converts to proton • Gamma • EM radiation • Accompanies other particles

  14. Electrons • Fundamental particle called a lepton http://en.wikipedia.org/wiki/Lepton • Electrical charge of -1 • Mass negligible(1⁄1836 of that of the proton) • Located outside the atomic nucleus in the electron cloud • Neutralizes the charge of the protons • Participates in chemical bonding

  15. Electron location within the Electron Cloud • Distance from atomic nucleus indicates electron energy level • The farther from the nucleus, the higher the energy • Levels called shells (1st quantum number,N) • Named as numbers (1,2,3…) • Maximum number of electrons in each shell= 2N2 • Outer shell=valence shell • Outer shell electrons most readily available for chemical bonding

  16. Electron location within the Electron Cloud • Orbitals (2nd quantum number (l) • Specific region in which an electron is likely to be found • Named with letters • s- sharp • p-principal • d- diffuse • f-fundamental • Named after groups of lines in the spectra of alkali metals

  17. Electron location within the Electron Cloud • Shapes of orbitals • s spherical- 2 electrons • p party balloons- 6 e- • d complex 10 e- • f complex 14 e- • Energy increases from s-f • Electrons usually fill from s→f with some exceptions • 3rd quantum number is the axis or magnetic orientation of the orbital (m)

  18. Electron Fill • Electron configuration of an element • Fill from lowest energy to highest energy location • Opposite spins for electrons in same orbital (Pauli exclusion principle) • Spin is the 4th quantum number (s) • http://intro.chem.okstate.edu/workshopfolder/electronconfnew.html

  19. Sub Atomic Particles

  20. Periodic table • Periods • Horizontal rows • Represent electron filling of a shell • Fill from left to right • s 1st 2 groups • d transition metal • p right block, metaloids, non metals • f lanthides and actinides

  21. Electron configurations • C • N • O • Li • Cl • F • Ne

  22. Bohr Model • C • N • O • Li • Cl • F • Ne

  23. Chemical bonding • Forms by interactions between valence shell electrons • Goal- full valence shell • Two main types • Ionic • Covalent • Type determined by electro negativity differential

  24. Ionic Bonds • Electron transfer • Large electro negativity differential • Between metals and non metals • Ions formed • Cation • Anion • Attraction between oppositely charged ions

  25. Covalent Bonds • Electrons shared between atoms • Low electro negativity differential • Hybrid orbitals • Electron timeshare • Single • Double • Triple

  26. Polar Covalent Bonds • Electrons not shared equally • Creates a dipole • Rotates in electrical field • Fosters dipole interactions

  27. Non-Polar Covalent Bonds • No separation of charges • Equal electron sharing • Even distribution of charges • Fosters induced dipole interactions

  28. Dipole Interactions • Occur between polar covalent molecules • Stronger than interactions between non-polar molecules • Slightly negative region of one molecule is attracted to slightly positive region of a neighboring molecule • Cohesive

  29. Hydrogen Bonds • Special type of dipole interaction • Involves H as the slightly + component • Very significant in biological systems • 2 strands of DNA • Protein shape • Genetic code

  30. Induced Dipole Interactions • May be referred to as Van der Waals interactions • Very weak • Between non-polar covalent molecules • Volatility of non-polars compared to polars

  31. Induced Dipole Interaction

  32. Solubility • Like dissolves like • Test for polar substance- dissolve in water • Non polar solvents clean non polar stains • Polar solvents clean polar stains • Oil and water

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