Chapter 4

1. Chapter 4 Atoms, Ions, and Compounds

2. The Composition of Compounds • The law of multiple proportions states that the masses of element Y that combine with a fixed mass of elements X to form two or more different compounds are in the ratios of small whole numbers. • Examples: NO, NO2, N2O, N2O5, etc.

3. Atomic Structure • J. J. Thomson discovered the subatomic particle know as the electron. • Thomson used cathode ray tube.

4. Mass of An Electron • Robert Millikan determined the mass of an electron with his oil-droplet experiment.

5. Thomson Model of the Atom • J. J. Thomson’s Plum-pudding model of the atom.

6. Radioactivity and the Nuclear Atom • Henri Becquerel discovered that some samples produced invisible radiation. • One type is a steam of beta () particles (high energy electrons). • A second type consists of alpha () particles, which have a +2 charge and a mass equivalent to that of a helium nucleus.

7. Rutherford’s Experiment • Rutherford and two of his students bombarded a thin foil of gold with  particles to test Thomson’s model of the atom. • Theory would predict that the  particles would travel through the foil without deflection, but the results didn’t confirm the model.

8. Rutherford’s Experiment

9. The Nuclear Atom • The nucleus of an atom contains all the positive charge and nearly all the mass in an atom. • The nucleus is about 1/10,000 the size of the atom. • A proton is a positively charged subatomic particle present in the nucleus of an atom.

10. The Third Subatomic Particle • A neutron is an electrically neutral or uncharged subatomic particle found in the nucleus of an atom. • Atomic Mass Units (amu) comprise a relative scale used to express the masses of atoms and subatomic particles. • The scale is based on the definition that the mass of 1 atom of carbon with 6 protons and 6 neutrons in its nucleus is exactly 12 amu.

11. Aston’s Experiment • Francis W. Aston built a postive-ray analyzer. • Data from neon gas samples demonstrated that two different kinds of atoms or isotopes existed. • Isotopes are atoms of an element whose nuclei have the same number of protons but different numbers of neutrons.

12. Aston’s Positive-ray Analyzer

13. Elements • Elements are pure substances made up of identical atoms. • There are 115 known kinds of atoms. Each has its own symbol. • The first character in an atoms symbol is an uppercase letter that corresponds the first letter of the elements name. • Most elements have a second character in their symbol which is is a lowercase letter usually the second letter of the elements name.

14. Element Names Elements discovered long ago have names and symbols with Latin or other origins, such as Au for gold (from aurum, meaning “bright dawn”), or Pb for lead (plumbum). Tungsten has a symbol of W, which is the first letter of its German name, wolfram. Symbol and names for the known atoms are given in Table 2.1.

15. The symbol and names for the known atoms are given in Table 2.1.

16. Symbols of Isotopes • Each element consists of atoms with the same number of protons in the nucleus. This number is called atomic number (Z). • Protons and neutrons in atomic nuclei are called nucleons. • The mass number (A) is the total number nucleons in one atom of an element.

17. A X Z Writing the Symbol of an Isotope • A is the mass number • Z is the atomic number • X is the atomic symbol

18. Average Atomic Masses • A mass spectrometer is an instrument that measures precise masses and relative amounts of ions of atoms and molecule. • The natural abundance of an isotope is its relative proportion among all the isotopes found a natural sample. • The average atomic mass of an element is calculated by multiplying the natural abundance of each isotope by its exact mass in atomic mass units and then summing these products.

19. Example Neon is found in three isotopes in nature. 19.9924 x 0.904838 = 18.0898323 amu 20.99395 x 0.002696 = 0.056599689 amu 21.9914 x 0.092465 = 2.033434801 amu 20.1797 amu

20. Mendeleev’s Periodic Table • Dmitrii I. Mendeleev arranged elements in the periodic table by their chemical and physical properties. • He left open spaces in his periodic table to account for elements not yet discovered.

21. The Modern Periodic Table • The modern periodic table is also based on a classification of elements in terms of their physical and chemical properties. • The horizontal rows are called periods. • Columns contain elements of the same family or group. • Transition metals are the elements in group 3 through 12 in the periodic table.

23. Groups of Elements • Group 1 contains the alkali metals. • Group 2 contains the alkaline earth metals. • Group 17 contains the halogens.

24. Broad Categories of Elements • Metals are elements on the left-hand side of the table. • Metals are shiny solids that conduct heat and electricity well and are malleable and ductile. • Nonmetals have properties opposite to those of the metals and are on the right side of table • Metalloids are the elements between the metals and nonmetals.

25. Continued • Main group elements or representative elements are the elements in groups 1,2 and 13 through 18. • The noble gases are the elements in Group 18.

26. Kinds of Compounds • Molecular Compounds are composed of atoms held together by covalent bonds. • Covalent bonds are shared pairs of electrons that chemically bond atoms together. • Ionic Compounds are composed of positively and negatively charged ions that are held together by electrostatic attraction. • Ions with negative charge are called anions. • Ions with positive charge are called cations.

27. Continued • Molecular compounds are made of nonmetals • Ionic compounds are made of a metal and a nonmetal. • Metal form cations and nonmetals form anions.

28. Terms • Molecular formulas describe the exact number and type of atoms present in one molecule of a compound. • An empirical formula gives the simplest whole-number ratio of elements in a compound. • The formula unit of an ionic compound is the smallest electrically neutral unit within the crystal of the compound.

29. NOMENCLATURE I. Binary Ionic compounds Binarymeans two different elements Ionicmeans metal and nonmetal Step 1 First give the name of the metal, followed by the nonmetal name using the “ide” suffix. Step 2 If the metal is to the right of group IIA, then a Roman numeral is used after the metal to to describe the charge of the metal. Except Ag, Zn,and Al Examples NaCl Al2O3 FeCl2 FeCl3

30. NOMENCLATURE I. Binary Ionic compounds Binarymeans two different elements Ionicmeans metal and nonmetal Step 1 First give the name of the metal, followed by the nonmetal name using the “ide” suffix. Step 2 If the metal is to the right of group IIA, then a Roman numeral is used after the metal to to describe the charge of the metal. Except Ag, Zn,and Al Examples NaCl Sodium chloride Al2O3 FeCl2 FeCl3

31. NOMENCLATURE I. Binary Ionic compounds Binarymeans two different elements Ionicmeans metal and nonmetal Step 1 First give the name of the metal, followed by the nonmetal name using the “ide” suffix. Step 2 If the metal is to the right of group IIA, then a Roman numeral is used after the metal to to describe the charge of the metal. Except Ag, Zn,and Al Examples NaCl Sodium chloride Al2O3Aluminum oxide FeCl2 FeCl3

32. NOMENCLATURE I. Binary Ionic compounds Binarymeans two different elements Ionicmeans metal and nonmetal Step 1 First give the name of the metal, followed by the nonmetal name using the “ide” suffix. Step 2 If the metal is to the right of group IIA, then a Roman numeral is used after the metal to to describe the charge of the metal. Except Ag, Zn,and Al Examples NaCl Sodium chloride Al2O3Aluminum oxide FeCl2 Iron(II) chlorideFeCl3

33. NOMENCLATURE I. Binary Ionic compounds Binarymeans two different elements Ionicmeans metal and nonmetal Step 1 First give the name of the metal, followed by the nonmetal name using the “ide” suffix. Step 2 If the metal is to the right of group IIA, then a Roman numeral is used after the metal to to describe the charge of the metal. Except Ag, Zn,and Al Examples NaCl Sodium chloride Al2O3Aluminum oxide FeCl2 Iron(II) chlorideFeCl3 iron(III) chloride

34. II. Nonbinary Ionic compounds Nonbinarymeans more than two different elements Step 1 First give the name of the metal, followed by the memorized polyatomic ion name. Step 2 If the metal is to the right of group IIA, then a Roman numeral is used after the metal to describe the charge of the metal. Except Ag, Zn, and Al. Examples NaOH Fe(NO3)3 Zn(C2H3O2)2 Fe(SO4)2

35. Memorized Polyatomic Ion List

36. II. Nonbinary Ionic compounds Nonbinarymeans more than two different elements Step 1 First give the name of the metal, followed by the memorized polyatomic ion name. Step 2 CO If the metal is to the right of group IIA, then a Roman numeral is used after the metal to describe the charge of the metal. Except Ag, Zn, and Al. Examples NaOH Fe(NO3)3 Sodium hydroxide Zn(C2H3O2)2 Fe(SO4)2

37. II. Nonbinary Ionic compounds Nonbinarymeans more than two different elements Step 1 First give the name of the metal, followed by the memorized polyatomic ion name. Step 2 If the metal is to the right of group IIA, then a Roman numeral is used after the metal to describe the charge of the metal. Except Ag, Zn, and Al. Examples NaOH Fe(NO3)3 Sodium hydroxide Iron(III) nitrate Zn(C2H3O2)2 Fe(SO4)2

38. II. Nonbinary Ionic compounds Nonbinarymeans more than two different elements Step 1 First give the name of the metal, followed by the memorized polyatomic ion name. Step 2 If the metal is to the right of group IIA, then a Roman numeral is used after the metal to describe the charge of the metal. Except Ag, Zn, and Al. Examples NaOH Fe(NO3)3 Sodium hydroxide Iron(III) nitrate Zn(C2H3O2)2 Fe(SO4)2 Iron(II) sulfate

39. II. Nonbinary Ionic compounds Nonbinarymeans more than two different elements Step 1 First give the name of the metal, followed by the memorized polyatomic ion name. Step 2 If the metal is to the right of group IIA, then a Roman numeral is used after the metal to describe the charge of the metal. Except Ag, Zn, and Al. Examples NaOH Fe(NO3)3 Sodium hydroxide Iron(III) nitrate Zn(C2H3O2)2 Fe(SO4)2 Iron(II) sulfate Iron(II) sulfate

40. III. Binary molecular Compounds Molecularmeans nonmetals Step 1 First give the name of the first nonmetal, followed by the nonmetal name using the “ide” suffix. Step 2 Give each nonmetal a Latin prefix describing the number of atoms present in the compound. Examples CO CO2 P2O5 CCl4

41. You will need to learn the Greek numerical prefixes (Table 4.6): *Note 1 Compound names never start with mono Note 2 When adding a prefix two vowls cannot next to each other

42. III. Binary Molecular Compounds Molecularmeans nonmetals Step 1 First give the name of the first nonmetal, followed by the nonmetal name using the “ide” suffix. Step 2 Give each nonmetal a Latin prefix describing the number of atoms present in the compound. Examples CO Carbon monoxide CO2 P2O5 CCl4

43. III. Binary Molecular Compounds Molecularmeans nonmetals Step 1 First give the name of the first nonmetal, followed by the nonmetal name using the “ide” suffix. Step 2 Give each nonmetal a Latin prefix describing the number of atoms present in the compound. Examples CO Carbon monoxide CO2 Carbon dioxide P2O5 CCl4

44. III. Binary Molecular Compounds Molecularmeans nonmetals Step 1 First give the name of the first nonmetal, followed by the nonmetal name using the “ide” suffix. Step 2 Give each nonmetal a Latin prefix describing the number of atoms present in the compound. Examples CO Carbon monoxide CO2 Carbon dioxide P2O5 CCl4

45. II. Binary Ionic molecular Molecularmeans combination of nonmetals Step 1 First give the name of the first nonmetal, followed by the nonmetal name using the “ide” suffix. Step 2 Give each nonmetal a Latin prefix describing the number of atoms present in the compound. Examples CO Carbon monoxide CO2 Carbon dioxide P2O5 Diphosphorus Pentoxide CCl4

46. II. Binary Ionic molecular Molecularmeans combination of nonmetals Step 1 First give the name of the first nonmetal, followed by the nonmetal name using the “ide” suffix. Step 2 Give each nonmetal a Latin prefix describing the number of atoms present in the compound. Examples CO Carbon monoxide CO2 Carbon dioxide P2O5 Diphosphorus Pentoxide CCl4 Carbon tetrachloride

47. III. Nonbinary Molecular Compounds Note:Do not use Latin prefixes Step 1 Write down the memorized polyatomic ions present in the compound. Step 2 Look to see if any monatomic ions are present. If so, then cations use the normal name. If it is an anion, then its name comes last with the “ide” suffix. Examples NH4Cl NH4OH

48. III. Nonbinary Molecular Compounds Note:Do not use Latin prefixes Step 1 Write down the memorized polyatomic ions present in the compound. Step 2 Look to see if any monatomic ions are present. If so, then cations use the normal name. If it is an anion, then its name comes last with the “ide” suffix. Examples Ammonium chloride NH4Cl NH4OH

49. III. Nonbinary Molecular Compounds Note:Do not use Latin prefixes Step 1 Write down the memorized polyatomic ions present in the compound. Step 2 Look to see if any monatomic ions are present. If so, then cations use the normal name. If it is an anion, then its name comes last with the “ide” suffix. Examples Ammonium chloride NH4Cl Ammonium hydroxide NH4OH

50. Compounds that Start with Hydrogen Case 1 If the anion ends in “ide” and it is aqueous, then use the prefix hydro and suffix “ic acid” Case 2 If the anion ends in “ate” then drop it and add the suffix “ic acid” Case 3 If the anion ends in “ite” then drop it and add the suffix “ous acid” Case 4 If the anion ends in” ide” and is a gas, or liquid, then leave the name and do not use Latin prefiex