1. 1 Chemistry Second Edition Julia Burdge Lecture PowerPoints Jason A. Kautz University of Nebraska-Lincoln Copyright (c) The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 2 Atoms, Molecules, and Ions

2. 2 2.1The Atomic Theory 2.2The Structure of the Atom Discovery of the Electron Radioactivity The Proton and the Nucleus Nuclear Model of the Atom The Neutron 2.3Atomic Number, Mass Number, and Isotopes 2.4The Periodic Table 2.5The Atomic Mass Scale and Average Atomic Mass 2.6Molecules and Molecular Compounds Molecules Molecular Formulas Naming Molecular Compounds Empirical Formulas 2.7Ions and Ionic Compounds Atomic Ions Polyatomic Ions Formulas of Ionic Compounds Naming of Ionic Compounds Hydrates Familiar Inorganic Compounds

3. The Atomic Theory In 1808, John Dalton formulated a precise definition of matter that we call atoms: 1)Elements are composed of extremely small particles called atoms. All atoms of a given element are identical. The atoms of one element are different from the atoms of all other elements. 2)Compounds are composed of atoms of more than one element. In any given compound the same types of atoms are always present in the same relative numbers. 3)A chemical reaction rearranges atoms in chemical compounds; it does not create or destroy them. 2.1

4. The Atomic Theory In the reaction below: All the oxygen molecules appear identical to one another (hypothesis 1). The compound CO 2 forms when each carbon atoms combines with two oxygen atoms (hypothesis 2). All atoms present before the reaction are also present after the reaction (hypothesis 3).

5. The Atomic Theory According to Proust’s law of definite proportions, different samples of a given compound always contain the same elements in the same mass ratio. SampleMass of O (g)Mass of C (g)Ratio (g O : g C) 123 g carbon dioxide89.433.62.66:1 50.5 g carbon dioxide36.713.82.66:1 88.6 g carbon dioxide64.424.22.66:1

6. The Atomic Theory According to the law of multiple proportions, if two elements can combine to form more than one compound with each other, the masses of one element that combine with a fixed mass of the other element are in ratios of small whole numbers. 1 2 = 1 2 = O to C ratio in CO O to C ratio in CO 2

7. The Structure of the Atom Based on Dalton’s atomic theory, an atom is the basic unit of an element that can enter into a chemical combination. 2.2

8. The Structure of the Atom When metal plates are connected to a high-voltage source, the negatively charged plate, or cathode, emits an invisible ray. The cathode ray is drawn to the anode. Cathode (-) Anode (+)

9. The Structure of the Atom Cathode rays may be deflected by magnetic or electric fields. Particles are negatively charged and are known as electrons.

10. The Structure of the Atom J. J. Thomson determined the charge to mass ratio of an electron: charge : mass = 1.76 × 10 8 C/g C stands for coulomb which is the derived SI unit for charge

11. The Structure of the Atom R. A. Millikan measured the charge of an electron with great precision.

12. The Structure of the Atom Three types of decay particles produced by radioactive decay include: Alpha (α) rays; positively charged Beta (β) rays; negatively charge Gamma (γ) rays; no charge; very high energy waves

13. The Structure of the Atom Ernest Rutherford used α particles to prove the structure of atoms. The majority of particles penetrated the gold foil undeflected. Sometimes, α particles were deflected at a large angle. Sometimes, α particles bounced back in the direction from which they had come.

14. The Structure of the Atom Rutherford proposed a new model for the atom: Positive charge is concentrated in the nucleus The nucleus accounts for most of an atom’s mass and is an extremely dense central core within the atom A typical atomic radius is about 100 pm A typical nucleus has a radius of about 5 x 10 –3 pm 1 pm = 1 x 10 –12 m

15. The Structure of the Atom Protons are positively charged particles found in the nucleus. Neutrons are electronically neutral particles found in the nucleus. Neutrons are slightly larger than protons.

16. Atomic Number, Mass Number, and Isotopes Elemental symbol All atoms can be identified by the number of protons and neutrons they contain. The atomic number (Z) is the number of protons in the nucleus The mass number (A) is the total number of protons and neutrons. Mass number (number of protons + neutrons) Atomic number (number of protons) 2.3

17. Atomic Number, Mass Number, and Isotopes Most elements have two or more isotopes, atoms that have the same atomic number but different mass numbers. hydrogen 1 proton 0 neutrons deuterium 1 proton 1 neutron tritium 1 proton 2 neutrons Isotopes of the same element exhibit similar chemical properties, forming the same types of compounds and displaying similar reactivities.

18. Atomic Number, Mass Number, and Isotopes How many protons neutrons and electrons are in an atom of boron-10? Solution: Atomic number (Z) = 5 Mass number (A) = 10 Protons = 5 (atomic number) Electrons = 5 (same number of protons and electrons in an atom) Neutrons = 5 (mass number – atomic number; 10 – 5 = 5)

19. The Periodic Table The periodic table is a chart in which elements having similar chemical and physical properties are grouped together. 2.4

20. The Periodic Table Elements are grouped in horizontal rows called periods. Vertical columns are called groups or families.

21. Elements can be categorized as metals, nonmentals or metalloids. Metals are good conductors of heat and electricity. Nonmetals are poor conductors of heat or electricity. Metalloids have Intermediate properties. The Periodic Table

22. The Atomic Mass Scale and Average Atomic Mass The most direct way to measure molecular mass is in a mass spectrometer. 2.5

23. The Atomic Mass Scale and Average Atomic Mass

24. Atomic mass is the mass of an atom in atomic mass units (amu). 1 amu = 1/12 the mass of a carbon-12 atom The atomic weight on the periodic table represents the average mass of the naturally occurring mixture of isotopes. Average mass (C) = (0.9893)(12.00000 amu) + (0.0107)(13.003355 amu) Average mass (C) = 12.01 amu Isotope Isotopic mass (amu) Natural abundance (%) 12 C12.0000098.93 13 C13.0033551.07 The Atomic Mass Scale and Average Atomic Mass

25. The atomic mass and natural abundances of the two stable isotopes of copper are given below. Calculate the average atomic mass. Solution: Average mass (Cu) = (0.6917)(62.929599 amu) + (0.3083)(64.927793 amu) Average mass (Cu) = 63.55 amu Isotope Isotopic mass (amu) Natural abundance (%) 63 Cu62.92959969.17 65 Cu64.92779330.83 The Atomic Mass Scale and Average Atomic Mass

26. Molecules and Molecular Compounds A molecule is a combination of at least two atoms in a specific arrangement held together by chemical forces (chemical bonds). A molecule may be an element or a compound. Diatomic molecules contain two atoms and may be either heteronuclear or homonuclear. Polyatomic molecules contain more than two atoms. 2.6

27. A chemical formula denotes the composition of the substance. A molecular formula shows the exact number of atoms of each element in a molecule. A structural formula shows not only the elemental composition, but also the general arrangements. Molecules and Molecular Compounds

28. Binary molecular compounds are substances that consist of just two different elements. Nomenclature: 1) Name the first element that appears in the formula 2) Name the second element that appears in the formula, changing its ending to –ide. Examples: HCl hydrogen chloride HIhydrogen iodide.

29. Molecules and Molecular Compounds Greek prefixes are used to denote the number of atoms of each element present. Examples: SO 2 sulfur dioxide COcarbon monoxide The prefix mono- is generally omitted for the first element. N 2 O 5 dinitrogen pentoxide

30. Molecules and Molecular Compounds Name the following binary molecular compounds: (a) Cl 2 O (b) SiCl 4 Solution: (a) Cl 2 Odichlorine monoxide (b) SiCl 4 silicone tetrachloride

31. Molecules and Molecular Compounds Write the formula for the following compounds (a) carbon disulfide (b) dinitrogen trioxide Solution: (a) CS 2 (b) N 2 O 3

32. Molecules and Molecular Compounds One definition of an acid is a substance that produces hydrogen ions (H + ) when dissolved in water. HCl is an example of a binary compound that is an acid when dissolved in water. To name these types of acids: 1) remove the –gen ending from hydrogen 2) change the –ide ending on the second element to –ic. hydrogen chloride + –ic acid → hydrochloric acid

33. Molecules and Molecular Compounds A compound must contain at least one ionizable hydrogen atom to be an acid upon dissolving. Examples: HFhydrofluoric acid HClhydrochloric acid HBrhydrobromic acid HIhydroiodic acid

34. Molecules and Molecular Compounds Organic compounds contain carbon and hydrogen, sometimes in combination with other atoms. Hydrocarbons contain only carbon and hydrogen The simplest hydrocarbons are called alkanes.

35. Molecules and Molecular Compounds Many organic compounds contain groups of atoms known as functional groups. Functional groups determine many of the chemical properties of a compound. Reactivity typically takes place at functional groups.

36. Molecules and Molecular Compounds

37. Molecular formulas give the exact number of each type of element in a compound. Empirical formulas give the simplest ratio of elements in a compound. CompoundMolecular FormulaEmpirical Formula waterH2OH2OH2OH2O hydrogen peroxideH2O2H2O2 HO benzeneC6H6C6H6 CH

38. Molecules and Molecular Compounds

39. Write the empirical formula for the following compound: C 8 H 10 N 4 O 2 Solution: Step 1:The elements are in an 8:10:4:2 ratio, which may be simplified to a 4:5:2:1 ratio (divide by the smallest number) Empirical formula C4H5N2O1C4H5N2O1

40. Ions and Ionic Compounds An atomic ion or monatomic ion is one that consists of just one atom with a positive or negative charge. The loss of one or more electrons from an atom yields a cation. Cations have a positive charge. Na AtomNa + Ion 11 protons 11 electrons10 electrons 2.7

41. Ions and Ionic Compounds An anion is an ion whose net charge is negative due to an increase in the number of electrons. Cl AtomCl – Ion 17 protons 17 electrons18 electrons

42. Ions and Ionic Compounds Atoms can lose or gain more than one electron.

43. Ions and Ionic Compounds A monatomic ion is named by changing the ending of the element’s name to –ide. Cl – is chlorideO 2– is oxide Some metals can form cations of more than one possible charge. Fe 2+ : ferrous ion [Fe(II)] Fe 3+ : ferric ion [Fe(III)] Mn 2+ : manganese(II) ion Mn 3+ : manganese(III) ion Mn 4+ : manganese(IV) ion

44. Ions and Ionic Compounds Ions that consist of a combination of two or more atoms are called polyatomic ions.

45. Ions and Ionic Compounds Formulas for ionic compounds are generally empirical formulas. Ionic compounds are electronically neutral.

46. Ions and Ionic Compounds Al 3+ O2–O2– Al 2 O 3 In order for ionic compounds to be electronically neutral, the sum of the charges on the cation and anion in each formula must be zero. Aluminum oxide: Sum of charges:2(+3) + 3(–2) = 0

47. Ions and Ionic Compounds To name ionic compounds: 1) Name the cation. omit the word ion use a Roman numeral if the cation can have more than one charge 2) Name the anion omit the word ion Examples: NaCN sodium cyanide FeCl 2 iron(II) chloride FeCl 3 iron(III) chloride

48. Ions and Ionic Compounds Name the following ionic compounds (a)Na 2 SO 4 (b)Cu(NO 3 ) 2 (c)CuNO 3 Solution: (a)sodium sulfate (b)copper(II) nitrate (c)copper(I) nitrate

49. Ions and Ionic Compounds Oxoanions are polyatomic anions that contain one or more oxygen atoms and one atom of another element. Starting with the oxoanions whose names end in –ate, the following can be used to name other oxoanions in the same family: 1) The ion with one more O atom than the –ate ion is called per... ate ion. (ClO 3 - is chlorate; ClO 4 - is perchlorate) 2) The ion with one less O atom than the –ate anion is called the –ite ion. (ClO 2 - is chlorite) 3) The ion with two fewer O atoms than the –ate ion is called the hypo... ite ion (ClO - is hypochlorite)

50. Ions and Ionic Compounds Oxoacids are acids that contain oxoanions. 1) An acid based on the –ate ion is called... ic acid HClO 3 is chloric acid 2) An acid based on the –ite ion is called... ous acid HClO 2 is chlorous acid 3) Prefixes in oxoanion names are retained in the name of the acid. HClO 4 is perchloric acid HClO is hypochlorous acid

51. Ions and Ionic Compounds Hydrates are compounds that have a specific number of water molecules within their solid structure. CuSO 4 5 H 2 Ocopper(II) sulfate pentahydrate

52. Chapter Summary: Key Points 2 The Atomic Theory Discovery of the Electron Radioactivity The Proton and the Nucleus Nuclear Model of the Atom The Neutron The Periodic Table Average Atomic Mass Molecular Formulas Naming Molecular Compounds Empirical Formulas Atomic Ions Polyatomic Ions Formulas of Ionic Compounds Naming Ionic Compounds Hydrates Inorganic Compounds