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Understanding Molecular Substances: Covalent and Ionic Compounds

This chapter delves into molecular substances, highlighting that most solid compounds at room temperature are ionic, while liquids and gases are typically covalent, with notable exceptions. Covalent compounds display considerable variability due to weaker bonds compared to ionic compounds. The chapter also explains molecular elements, allotropes, and methodologies like distillation for separation of substances. It provides insights into inorganic and organic compounds, molecular naming conventions, and the structure-function relationship in covalent bonding, particularly focusing on carbon's diverse allotropes.

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Understanding Molecular Substances: Covalent and Ionic Compounds

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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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