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Chapter 2

Chapter 2. The Nature of Molecules. What’s The Matter?. Anything that has mass and occupies space is matter Matter is composed of atoms. Bohr Model- Very Simple and Unrealistic. Atomic Mass vs Atomic Number. Atomic Number= Number of Protons

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Chapter 2

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  1. Chapter 2 The Nature of Molecules

  2. What’s The Matter? • Anything that has mass and occupies space is matter • Matter is composed of atoms

  3. Bohr Model- Very Simple and Unrealistic

  4. Atomic Mass vs Atomic Number • Atomic Number= Number of Protons • Atomic Mass = Number of Protons + Number of Neutrons Measured in Daltons • Measured in Daltons and also equal to 1 gram

  5. Are All Atoms Created Equal? • NOPE- Most atoms have no net charge because the number of protons and electrons are equal. • Ions- are charged due to a surplus of either electrons or protons • More electrons is a negatively charged ANION • More protons is a positives charged CATION

  6. What is an Isotope?

  7. Radioactive Isotopes- when nuclei are unstable and break up into smaller elements. • Half-Life- the amount of time it takes for ½ of an element to decay. **If you have a 14 gram sample of Carbon and the Half-Life of Carbon is 5,600 years How many grams of Carbon would you have in 22,200 years?** Answer= 0.875 grams

  8. Do We Know Exactly Where Electrons Are? • Nope, but we can make a good guess. • Orbital- the area around the nucleus where an electron can LIKELY be found

  9. Atoms Always Want to Move From Higher Energy to Lower Energy • Lowest energy closest to the nucleus • Highest energy farthest from the nucleus. • Lowest to highest Energy- s, p , d, f • S can hold 2 electrons • P can hold 6 • D can hold 10 • F can hold 14

  10. Practice Problems • Find the electron configurations for Nitrogen, Selenium, and Krypton

  11. Oxidation vs Reduction • Oxidation= Loss of an electron • Reduction = Gain of an electron

  12. Mendeleev • Mendeleev created the periodic table and organized it according to how the outer electrons of elements interacted. • Atoms tend to completely fill their outer electron level with 8 electrons.

  13. Ionic Vs Covalent Bonds • Ionic- form when atoms with opposite electrical charges attract • Form salts and crystals • Covalent- shares electrons, has no net charge, no free electrons, and the octet rule is satisfied. • Can have single, double, or triple covalent bonds

  14. Chemical Reactions • Things that affect the rate of chemical reactions • Temperature= increase temperature increase rate • Concentration of Reactants and Products- proceed to equilibrium • Catalysts- Lower activation energy to speed reactions.

  15. Water Water Everywhere

  16. pH • Acids- has more H+ pH of 0-6 • Bases- has more OH- pH of 8-14 • Neutral= pH of 7 • Buffer- acts as a reservoir for hydrogen ions donating them to a solution when their concentration falls taking them from the solution when their concentration rises

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