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Chapter 5.2

Chapter 5.2. Molecular Substances. Most solid compounds at room temperature are ionic. Most liquid and gas compounds at room temperature are covalent . There are exceptions to these rules. Exceptions: solid covalent cpds. Sugar Moth balls Sand Butter.

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Chapter 5.2

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  1. Chapter 5.2 Molecular Substances

  2. Most solid compounds at room temperature are ionic. • Most liquid and gas compounds at room temperature arecovalent. • There are exceptions to these rules. • Exceptions: solid covalent cpds. • Sugar • Moth balls • Sand • Butter

  3. Covalent compounds/molecules are much more variable than ionic cpds. • Differences due to fact that covalent bonds are weaker than ionic bonds. • Covalent compounds react very differently due to different bond strengths. • Ex: diamonds- hard, carbons tightly bound to each other • crayons and wax- soft and have low melting point due to weak bonds

  4. Separation of Substances • Distillation: • Method of separating substances in a mixture by • evaporation of the liquid and condensation of its vapor

  5. Molecular Elements • I. Molecular Element: • molecule with two or more of the same element • - Diatomic elements: 2 of same elements in a cpd. • 7 found naturally in diatomic state • H2 gas at RT H : H • N2 “ “ N ::: N • O2 “ “ O :: O • F2 “ “ F : F • Cl2 “ “ Cl : Cl • I2 solid at RT I : I • Br2 liquid at RT Br : Br • WHY ARE THESE NOT FOUND AS MONOATOMIC ELEMENTS?

  6. Allotropes: • forms of elements that differ in the way the atoms are bonded • - have different structures of the same element • - properties of allotropes differ from the single element and from other allotropes

  7. Allotropes • A.Oxygen Allotropes • O2 (diatomic) O=O • Ozone (O3) • O2 + O  O3 • - formed by: • O2 + uv light or lightning • O2 + pollution (smog) • layer in upper atmosphere, filters out harmful UV light

  8. B.Carbon Allotropes - most versatile element in forming different structures of covalent bonds (4 valence electrons) can make more covalent bond formations than any other element Eight allotropes of carbon: a) Diamond b) Graphite c) Lonsdaleite d) Buckyball C60 e) C540, f) C70g) Amorphous carbon h) Single-walled carbon nanotube Allotropes

  9. Phosphorous Allotropes • - white: ignites in air, • flares • - black: semiconductors • - red: match sticks • * differences result from temperature and pressure during formation

  10. Formulas and Names of Molecular Compounds • Types Molecular Compounds • Inorganic: no carbon • ex: HCl, NO2, H2O, SO4 • 2. Organic: contain carbon • ex: CO2, C2H6O3, CH4, CCl4

  11. Naming Inorganic Compounds • Rules • 1. Write name of first non metal • 2. Write name of second non metal and change ending to “ide” • - first element should be further left on periodic table (except H) • - if both in same group, first element should be closer to bottom of periodic table • 3. Add a prefix to each element to tell how many atoms of each element are present • - if first element has only 1 atom, not necessary to write “mono” • 4. If using prefix “mono” and o-o or o-a are next to each other, drop the first “o” or “a” • ex: monooxide  monoxide • pentaoxide  pentoxide

  12. Write the names of the following molecules:

  13. Write the formulas for the following molecules:

  14. Formal vs Common Names • Formal Name • tells chemical composition of compound • ex: CCl4 carbon tetrachloride • NaCl sodium chloride • H2O dinitrogen monoxide • Common Name • “nickname”, easier to say, does not tell composition • ex: NaCl salt • H2O water • HCl hydrochloric acid • H2SO4 sulfuric acid • HNO3 nitric acid • NH3 ammonia

  15. Organic Compounds • Contains carbon • Names based on hydrocarbon bonds (H-C) • Hydrocarbon: organic compound that contains only hydrogen and carbon atoms • Found in fossil fuels (gas, petroleum) • Form long chains as compounds • Ex: CH4 methane • C3H8 propane • C4H10 butane • C8H18 octane

  16. Study for the test !

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