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Atoms, Molecules & Ions

Atoms, Molecules & Ions. AP Chemistry Chapter 2.1 (Days 3 & 4). Subatomic Particles. Protons and electrons are the only particles that have a charge. Protons and neutrons have essentially the same mass. The mass of an electron is so small we ignore it. Symbols of Elements.

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Atoms, Molecules & Ions

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  1. Atoms, Molecules & Ions AP Chemistry Chapter 2.1 (Days 3 & 4)

  2. Subatomic Particles • Protons and electrons are the only particles that have a charge. • Protons and neutrons have essentially the same mass. • The mass of an electron is so small we ignore it.

  3. Symbols of Elements Elements are symbolized by one or two letters.

  4. Atomic Number All atoms of the same element have the same number of protons: The atomic number (Z) In a neutral atom, the # of p+ = the # of e-

  5. Atomic Mass The mass of an atom in atomic mass units (amu) is the total number of protons and neutrons in the atom. Remember, electron mass is so tiny we essentially ignore it.

  6. Atoms of the same element with different masses. Isotopes have different numbers of neutrons. 11 6 12 6 13 6 14 6 C C C C Isotopes

  7. How many neutrons are there in an atom of 14C? 6 8 12 14

  8. Correct Answer: 6 8 12 14 14 Mass number C 6 Atomic number The difference between the mass number and the atomic number is the number of neutrons (14  6) = 8.

  9. Determining the Number of Subatomic Particles in Atoms How many protons, neutrons, and electrons are in (a) an atom of 197Au (b) an atom of strontium-90?

  10. Determining the Number of Subatomic Particles in Atoms How many protons, neutrons, and electrons are in (a) a 138Ba atom, (b) an atom of phosphorus-31? Answer: (a) 56 protons, 56 electrons, and 82 neutrons; (b) 15 protons, 15 electrons, and 16 neutrons.

  11. Periodic Table • A systematic catalog of elements. • Elements are arranged in order of atomic number.

  12. Periodicity When one looks at the chemical properties of elements, one notices a repeating pattern of reactivities.

  13. Periodic Table • The rows on the periodic chart are periods or series. • Columns are groups or families. • Elements in the same group have similar chemical properties.

  14. Groups These five groups are known by their names.

  15. Solids, Liquids, & Gases

  16. Metals, Nonmetals, Semimetals Metals – good conductors, high luster, ductile, malleable

  17. Metals, Nonmetals, Semimetals Nonmetals – most are gases, poor conductors, brittle

  18. Metals, Nonmetals, Semimetals Semi-metals (metalloids) – have properties similar to metals and nonmetals

  19. Diatomic Molecules These seven elements occur naturally as molecules containing two atoms: • Hydrogen & draw a 7 starting at N (element 7) • Hockey stick & puck • BrINClHOF (Brinklehoff) • IHave No Bright Or Clever Friends

  20. Compounds and Chemical Formulas Molecule - A single particle, contains two or more nonmetal atoms; covalently bonded Formula Unit – a particle containing a metal with a nonmetal; ionicly bonded Chemical formulas– give the number of atoms of each element in a compound

  21. Identifying Ionic and Molecular Compounds Which of the following compounds would you expect to be ionic: N2O, Na2O, CaCl2, SF4? Which of the following compounds are molecular: CBr4, FeS, P4 O6, PbF2 ? Answer: CBr4 and P4 O6

  22. Identifying Ionic and Molecular Compounds Which of the following compounds are molecular: CBr4, FeS, P4 O6, PbF2 ? Answer: CBr4 and P4 O6

  23. Which combination is likely to produce an ionic compound? • C and H • S and Cl • Ca and F • Br and I • Xe and F

  24. Which combination is likely to produce an ionic compound? • C and H • S and Cl • Ca and F • Br and I • Xe and F

  25. Chemical formulas – give the number of atoms of each element in a compound Compounds and Chemical Formulas

  26. Compounds and Chemical Formulas State the composition for a molecule of trinitrotoluene, TNT: C7H5(NO2)3 7 carbon atoms, 5 hydrogen atoms, 3 nitrogen atoms, 6 oxygen atoms; 21 atoms total

  27. Types of Formulas • Empirical formulas give the lowest whole-number ratio of atoms of each element in a compound. • Molecular formulas give the exact number of atoms of each element in a compound. • Sometimes they can be the same

  28. Relating Empirical and Molecular Formulas Write the empirical formulas for the following molecules: (a) glucose, a substance also known as either blood sugar or dextrose, whose molecular formula is C6H12O6; (b) nitrous oxide, a substance used as an anesthetic and commonly called laughing gas, whose molecular formula is N2O. Answer:  BH3 Give the empirical formula for the substance called diborane, whose molecular formula is B2H6.

  29. Relating Empirical and Molecular Formulas Give the empirical formula for the substance called diborane, whose molecular formula is B2H6. Answer:  BH3

  30. C2H6 • CH3

  31. Ions • When atoms lose or gain electrons, they become ions.

  32. Ions • Cation – positive ion • Has the “t” like a + sign • Formed by metals and some nonmetals • Lost electrons • #p+ > #e- • Anion – negative ion • Gained electrons • Formed by nonmetals • #p+ < #e- • Polyatomic ions • Made up of two or more atoms • Can be positive or negative

  33. An isotope of Cr3+ ion containing 24 protons and 27 neutrons would contain ___ electrons. 21 24 27 3

  34. Correct Answer: 21 24 27 3 The +3 charge indicates there are 3 more protons than electrons: 24 3 = 21

  35. Which of the following species has the greatest number of electrons? • Cl • Ca2+ • P3 • K • Ar

  36. Correct Answer: • Cl • Ca2+ • P3 • K • Ar K has 19 electrons; all the other species listed have only 18 electrons.

  37. Writing Chemical Symbols for Ions Give the chemical symbol, including mass number, for each of the following ions: (a) The ion with 22 protons, 26 neutrons, and 19 electrons; (b) the ion of sulfur that has 16 neutrons and 18 electrons. Solution(a) The symbol for the ion is 48Ti3+. (b) The symbol for the ion is 32S2–.

  38. Writing Chemical Symbols for Ions How many protons and electrons does the Se2– ion possess? Answer: 34 protons and 36 electrons

  39. Isoelectronic Atoms and ions are considered isoelectronic when they have the same number of electrons.

  40. 1. 2. 3. 4. None of the above 5. Which of the following are isoelectronic?

  41. 1. 2. 3. 4. None of the above 5. Which of the following are isoelectronic?

  42. Group 1A = 1+

  43. Group 2A = 2+

  44. Group 3A = 3+

  45. Group 5A = 3–

  46. Group 6A = 2–

  47. Group 7A = 1–

  48. Group 4A = varies

  49. Monoatomic Ions • Transition metals form more than one cation The Stock System • Iron can be Fe2+ or Fe3+ • Iron (II) ion, iron (III) ion • Cu+ and Cu2+

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