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Introduction to Chemistry

Introduction to Chemistry. Miller Levine – Chapter 2 sections 1 & 2. October 2013. Vocabulary. Atom – basic building block of matter Element - pure substance made up of only one kind of atom

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Introduction to Chemistry

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  1. Introduction to Chemistry Miller Levine – Chapter 2 sections 1 & 2 October 2013

  2. Vocabulary Atom – basic building block of matter Element - pure substance made up of only one kind of atom Compound - pure substance made up of 2 or more different atoms chemically combined in definite amounts.

  3. Formula - chemist’s abbreviation for the name of a compound. • Symbols - tells the kind of atoms found in the compound • Subscripts - tell the number of each atom found in the compound

  4. Symbols Symbol - chemist’s abbreviation for the name of an element (1) one or two letters (2) first letter UPPER case -secondletterlower case

  5. symbol H2CO3 subscript

  6. Elemental Facts: • 92 naturally occurring elements • 25 essential for life • 96% of living things -Carbon (C), oxygen (O), hydrogen (H), nitrogen (N) • most of remaining 4% -Calcium (Ca), phosphorus (P), potassium (K) and sulfur (S)

  7. Atomic StructureReview

  8. Protons Location - nucleus (center) charge - positive Mass - 1 amu Role – determines identity of atom

  9. Neutrons Location - nucleus (center) Charge - none Mass - 1 amu Role - determines the radioactivity of the atom

  10. Electrons Location - energy levels Charge - negative Mass – 0 amu Role – determines chemical activity: how atoms interact with other atoms

  11. Why do all three of these atoms represent the element carbon? What is different about each of these carbon atoms?

  12. Facts About Atoms • Atoms are electrically neutral. • # protons = # electrons. • If electrons are added or subtracted, atoms are changed into ions.

  13. Ion Charged atom negative ion – atom gains electrons positive ion – atom loses electrons

  14. Chemical Bonding

  15. Chemical properties depend upon how the electrons are arranged in an atom. • Atoms are not stableifthey do not have a filled last energy level. • Atoms achieve stability by interacting with other atoms forming chemical bonds.

  16. Arranging Electrons in an Atom • Electrons are found in energy levels outside the nucleus • Electrons fill lowest energy levels before occupying higher levels • 1st energy level can fit 2. • Remaining levels can fit 8.

  17. STOP and do activity sheet on page 3 of notes packet.

  18. octet rule: Elements tend to react to obtain an electron configuration of 8 electrons in highest energy level • Exception – hydrogen (2)

  19. Types of Bonds Ionic Nonpolar Covalent Polar Covalent

  20. Ionic Bonds Transfer of electrons from one atom to another Forms ions

  21. Covalent Bond • A chemical bond in which two atoms share a pair of electrons between them. • Each atom contributes one electron to the pair. • Represented by a line between the atoms (O-H)

  22. Types of Covalent Bonds • Polar • Nonpolar

  23. Nonpolar Covalent Bonds • mutual sharing of one or more pairs of electrons • Mutual attraction of both nuclei

  24. Polar Covalent Bonds • Sharing of electrons is uneven. • The pair of shared electrons spend more time orbiting the nucleus of the atom with the higher electronegativity. • Electronegativity – An atom’s ability to attract electrons within a bond.

  25. HCl • H – electronegativity – 2.1 • Cl – electronegativity – 3.0 • Electron pair spends more time orbiting the chlorine atom

  26. Process in which a chemical change occurs Reactants - beginning substances in a chemical reaction Products - new substances that are made as a result of a chemical reaction Chemical Reaction

  27. All chemical reactions involve energy. All chemical reactions need energy to start them. Activation energy – energy needed to start reaction Chemical Reactions & Energy

  28. Exothermic Reactions • Reactions that release more energy than is needed to start them.

  29. Endothermic Reactions • Reactions that constantly absorb energy from their surrounding because they need a source of energy to keep them going.

  30. Unique Properties of Water

  31. Structure of Water • Chemical formula - H2O • Electronegativity of H = 2.1 • Electronegativity of O = 3.5 • This causes the electrons to spend more time circling the oxygen atom than the hydrogen atom.

  32. - + + polar molecule - molecule in which opposite ends have opposite electric charges.

  33. Water is a polar molecule because the shared pair of electrons between hydrogen and oxygen spend more time orbiting oxygen nucleus than hydrogen nucleus • H end is positive • O end is negative • This causes hydrogen bonds to form between water molecules.

  34. Hydrogen bonds – weak attraction between the slightly positive hydrogen atoms of one molecule and the slightly negative molecules of another

  35. All of water’s unique life – supporting properties can be traced back to its polarity and the formation of hydrogen bonds between water molecules themselves and water and other molecules.

  36. Water is often called the universal solvent. • Because of its polarity, it dissolves both ionic and polar covalent compounds. • Only nonpolar covalent compounds do not dissolve well in water. • Many of the organic compounds dissolved in the watery cytoplasm of the cell are either acids or bases.

  37. Acids Release H+ (hydrogen ions) in solution. H+ are really protons.

  38. Bases Releases OH- ions in solution

  39. pH Scale Measures how strong acids and bases are Range of numbers – 0 - 14 pH of 7 is neutral, H+ concentration is equal to OH- concentration.

  40. acid range: 0-7 • base range: 7-14 • The further the pH is from 7, the stronger the acid or base.

  41. Since cells can only function within a very narrow pH range, all the acids and bases dissolved within them must be controlled by something.

  42. Buffers • Substances that cause a solution to resist changes in pH • Buffers work by accepting H+ when their levels rise and donating H+ when their level falls. • Importance: Buffers help maintain homeostasis inside cells.

  43. Citations • Elements of Chemistry: Atoms: The Building Blocks of Matter. United Learning. 2003.unitedstreaming. 23 August 2006<http://www.unitedstreaming.com/> • Physical Science Series: Chemical Bonding. United Learning. 1998.unitedstreaming. 23 August 2006<http://www.unitedstreaming.com/>

  44. Atom, components of. Paul Fuqua. 2004.unitedstreaming. 24 August 2006<http://www.unitedstreaming.com/> • Atom losing an electron. Paul Fuqua. 2004.unitedstreaming. 24 August 2006<http://www.unitedstreaming.com/> • Elements of Chemistry: Acids, Bases, and Salts. United Learning. 2003.unitedstreaming. 24 August 2006<http://www.unitedstreaming.com/>

  45. Sun over water. Paul Fuqua. 2003.unitedstreaming. 24 August 2006<http://www.unitedstreaming.com/> • pH meter used to study acid rain. Paul Fuqua. 2005.unitedstreaming. 24 August 2006http://www.unitedstreaming.com/ • Biology of Water, The: Water: A Miraculous Substance (The Properties of Water and the Development of Life). United Learning. 1991.unitedstreaming. 23 August 2006<http://www.unitedstreaming.com/>

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