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Mr. Ed’s Chemistry 9701

Mr. Ed’s Chemistry 9701. Term 1 Week 2. Chemical Reactivity. How reactive an element is depends on the electron configuration of its atoms. The electrons in the outer energy level are known as valence electrons Noble Gas configuration. The magic number 8: octet rule.

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Mr. Ed’s Chemistry 9701

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  1. Mr. Ed’s Chemistry9701 Term 1 Week 2

  2. Chemical Reactivity • How reactive an element is depends on the electron configuration of its atoms. • The electrons in the outer energy level are known as valence electrons • Noble Gas configuration. • The magic number 8: octet rule.

  3. Cations! . . . Again. • Group 1, 2, and 3: • Easy to loose 1, 2, or 3 electrons. • Become positively charged! • Group 1 always 1+ charge • Group 2 always 2+ • Group 3 . . . + + +

  4. Anions . . . • Group 5, 6, and 7: • Nitrogen family – Pnictogens. • Oxygen family – Chalcogens. • Halogens • Require 3, 2, or 1 electron for Nobel Gas • Negative charged

  5. Attraction • Positive and negative charges attract each other! • Think magnets!

  6. Naming . . . NomenclatureGreek number prefixes. • Mono- • Di- • Tri- • Tetra- • Penta- • Hexa- • Hepta- • Octa- • Nona- • Deca-

  7. Binary ionic compounds. • Made of just two elements • Is the compound ionic or molecular? • Compounds of metals with non-metals • Ionic

  8. Binary ionic compounds. • The cation named first • Just the metal’s name • Transition metal must always be followed by a Roman numeral • Followed by the name of the anion. • Mono- is never used for the first part.

  9. Binary ionic compounds. • If there is only one type of compound • Greek numbering is NOT used • Calcium bromide – CaBr2 • There is only one bromide of calcium • NOT calcium dibromide!

  10. Binary ionic compounds. • For naming anions • Element name and end in –ide

  11. Binary ionic compounds. Name • Sodium chloride • Copper(II) chloride • Zinc sulfide • Magnesium nitride • Potassium oxide • Aluminum sulfide Formula NaCl CuCl2 ZnS Mg3N2 K2O Al2S3

  12. Polyatomic ions. • A group of more than one atom as ion • Anions often end in –ate or –ite. • Cations . . . Few • Ammonia: NH3 – Ammonium NH4+ • Water: H2O – Hydronium H3O+ • Many cations end in -nium

  13. Polyatomic Ionic compounds. • Cation: Again just the metal’s name. • Ammonia: NH3 – Ammonium NH4+ • For transition metals: Again Roman numerals for oxidation state. • Second part of: Anion

  14. Ployatomic ionic compounds. • If there is only one type of compound • Greek numbering is NOT used • Calcium carbonate – Ca(NO3)2 • There is only one nitrate of calcium • NOT calcium dinitrate!

  15. Some common polyatomic cations. • You should know these! End in –ate. • OH– – hydroxide • NO3– – nitrate • SO42– – sulfate • CO32– – carbonate • HCO3– – hydrogencarbonate (bicarbonate) • PO43– – phosphate • ClO3– – chlorate

  16. Some more polyanions. • You might see these. • NO2– – Nitrite ion • SO32– – Sulfite ion • PO33– – Phosphite ion • ClO2– – Chlorite • End in -ite

  17. Why do ions form? • The driving force is . . . ENERGY!

  18. Why do ions form? • Electronegativity • A measure of the ability of an atom to attract electrons (or electron density) towards itself. • Proposed by Linus Pauling in 1932. • Two: Chemistry and Peace

  19. Why do ions form? • The scale 0.70 to 4.00 • 0.79 for Cesium . . . The least • 3.98 for Fluorine . . . The most • Size of atom • Charge of nucleus

  20. Viva la difference! • Differences in electronegativity (E.N.) • Two atoms of the same element: • E.N. = 0 • Electron are equally shared

  21. Viva la difference! • Differences in electronegativity (E.N.) • Two atoms of the same element: • E.N. = 0 • Electron are equally shared

  22. Viva la difference! • When both nuclei have same charge • Both also have same number of e– • And  same e– configuration • All forces are balanced • Non-polar covalent bond

  23. Viva la difference! • Differences in electronegativity (E.N.) • Two atoms are of different elements: • E.N. difference ≠ 0 • Electron are not equally shared • Most E.N. atom gets more of the e–

  24. Viva la difference! • Differences in electronegativity (E.N.) • E.N.  0.5 • Non-polar covalent • E.N.  0.5  2.1 • Polar covalent • E.N. above 2.1 • Ionic

  25. Some examples • Hydrogen – 2.20 • Alkali metals – least electronegative

  26. Some examples Francium: At any given time, as little as 30 g exists throughout the Earth’s entire crust. • Hydrogen – 2.20 • Alkali metals – least electronegative

  27. Some examples Astatine: Rarest naturally occurring element, less than 25 g exists at any one time in the Earth’s entire crust. • Halogens – most electronegative

  28. Some examples • Top six most electronegative

  29. Calculations • Easy – Just subtract E.N. values • NaCl • Cl = 3.16 and Na = 0.93 • 3.16 – 0.93 = 2.23 • Definitely ionic

  30. Calculations • MgO • O = 3.44 and Mg = 1.31 • 3.44 – 1.31 = 2.13 • Also definitely ionic

  31. Calculations • NH3 • N = 3.04 and H = 2.20 • 3.04 – 2.20 = 0.84 • Polar covalent • H→N←H ↑ H

  32. Calculations • H2O • O = 3.44 and H = 2.20 • 3.44 – 2.20 = 1.24 • Strongly polar covalent

  33. Calculations • CH4 • C = 2.55 and H = 2.20 • 2.55 – 2.20 = 0.35 • Non-polar covalent

  34. Fortunately . . . • For ionic compounds: No need to calculate. • Simple rules. • Compounds of metals: ionic • Metal – Non-metal • Groups I, II, most of III, Transitions, bottoms of IV, and V

  35. Fortunately . . . • Compounds of non-metals: Ionic or covalent • Non-metal – Non-metal • B, top of groups IV, and V, most of VI, and group VII. • Metal to metal? • Alloys Metal – Metal compounds are rare.

  36. Unfortunately . . . • Naming covalent compounds • Like ionic compounds usually has two parts • First part is the LEAST electronegative element • Just the element’s name Need no know at least first five most E. N.

  37. Covalent compounds . . . • Naming covalent compounds • Like ionic compounds usually has two parts • First part is the LEAST electronegative element • Just the element’s name Need no know at least first five most E. N.

  38. Ionic Bonds • Loss of electrons by one atom, gain of electrons by another • Oxidation Is Loss • Reduction Is Gain • Very strong bonds • Electrostatic • Can involve more than one electron OIL RIG Magnetic

  39. Ionic Solid Structure • Simple repeating structure • Ions alternate • Lattice • Giant structure • No one atom or ion bound to any other specific atom or ion

  40. Ionic Properties • High melting temperature • High boiling temperature • Usually Soluble in polar solvents • Electrically conductive when melted or dissolved • Crystalline – easily cleaved

  41. Electro-negativity: A measure of an atom’s tendency to gain electrons Related to: Electro-Chemical Series When do they form? • Great difference between the electro-negativities of elements involved • When little difference . . .

  42. → The least electronegative: Lower Left → The more electronegative elements: Upper Right

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