1. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e Chapter 2 Atoms and Elements Chemistry: A Molecular Approach, 2nd Ed. Nivaldo Tro Ms. Knick HAHS 1

2. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e Elements Each element has a unique number of protons in its nucleus The number of protons in the nucleus of an atom is called the atomic number the elements are arranged on the Periodic Table in order of their atomic numbers 2Tro: Chemistry: A Molecular Approach, 2/e

3. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e Electrons The number of electrons(-) must equal the number of protons(+) in a neutral atom. 3Tro: Chemistry: A Molecular Approach, 2/e

4. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e The Periodic Table of the Elements 4 The atomic number tells you how many protons are in the nucleus and how many electrons are in the atom Tro: Chemistry: A Molecular Approach, 2/e

5. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e Atomic Mass The atomic mass is the number of protons and neutrons. In order to determine the number of neutrons, subtract the atomic number from the atomic mass. 5 Atomic Number Atomic Mass

6. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e Complete the table below: ProtonsElectronsNeutronsAtomic Number Atomic Mass Elemental Symbol 7 32 Li 58 6

7. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e7 Structure of the Nucleus Soddy discovered that the same element could have atoms with different masses, which he called isotopes there are two isotopes of chlorine found in nature, one that has a mass of about 35 amu and another that weighs about 37 amu The observed mass is a weighted average of the weights of all the naturally occurring atoms the percentage of an element that is one isotope is called the isotope ’ s percent abundance If the atomic mass of chlorine is 35.45 amu, which isotope is more abundant, Cl-35 or Cl-37? Tro: Chemistry: A Molecular Approach, 2/e

8. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e8 Isotopes All isotopes of an element are chemically identical undergo the exact same chemical reactions All isotopes of an element have the same number of protons Isotopes of an element have different masses Isotopes of an element have different numbers of neutrons Isotopes are identified by their mass numbers, which is the sum of all the protons and neutrons in the nucleus Tro: Chemistry: A Molecular Approach, 2/e

9. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e9 Neon 9.25%221210Ne-22 or 0.27%211110Ne-21 or 90.48%2010 Ne-20 or Percent Natural Abundance A, Mass Number Number of Neutrons Number of ProtonsSymbol Tro: Chemistry: A Molecular Approach, 2/e

10. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e Practice: (EASY) Naturally occurring europium (Eu) consists of two isotopes with a mass of 151 g and 153 g. Europium-151 has an abundance of 48.03% and Europium-153 has an abundance of 51.97%. What is the atomic mass of europium? 10

11. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e Practice: (You must think….just a little) Silver has two isotopes. The first isotope is 51.83% abundant and has a mass of 106.905g. What is the mass of the second isotope? 11

12. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e Practice: (You must think….HARD) An imaginary element (Atomic mass 93.7140) has three naturally-occurring isotopes with isotopic masses of 92.9469, 93.2923 and 94.9030. The abundance of the lightest isotope is 42.38 %. What is the percentage abundance of the heaviest isotope? 12

13. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e13 Charged Atoms When atoms gain or lose electrons, they acquire a charge Charged atoms or groups of atoms are called ions When atoms gain electrons, they become negatively charged ions, called anions When atoms lose electrons, they become positively charged ions, called cations Tro: Chemistry: A Molecular Approach, 2/e

14. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e Ions and Compounds Ions behave much differently than the neutral atoms e.g., the metal sodium, made of neutral Na atoms, is highly reactive and quite unstable; however, the sodium cations, Na +, found in table salt are very nonreactive and stable Because materials such as table salt are neutral, there must be equal amounts of charge from cations and anions in them 14Tro: Chemistry: A Molecular Approach, 2/e

15. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e Complete the table below: ProtonsElectronsNeutronsElemental Symbol S -2 Ba +2 Li +1 Cl -1 15

16. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e Periodic Patterns LiBeBCNOF NaMgAlSiPSCl KCa H NMH 2 O a/b H2H2 1.0 MLi 2 O b LiH6.9 MNa 2 O b NaH23.0 MK2ObK2Ob KH39.1 MBeO a/b BeH 2 9.0 MMgO b MgH 2 24.3 MCaO b CaH 2 40.1 NMB2O3aB2O3a BH 3 10.8 M Al 2 O 3 a/b AlH 3 27.0 NMCO 2 a CH 4 12.0 M/NM SiO 2 a SiH 4 28.1 NMN2O5aN2O5a NH 3 14.0 NMP 4 O 10 a PH 3 31.0 NM H2SH2S 32.1 SO 3 a NM H2OH2O16.0 O2O2 NMCl 2 O 7 a HCl 35.5 NM HF19.0 a = acidic oxide, b = basic oxide, a/b = amphoteric oxide M = metal, NM = nonmetal, M/NM = metalloid 16Tro: Chemistry: A Molecular Approach, 2/e

17. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e17 About ¾ of the elements are classified as metals. They have a reflective surface, conduct heat and electricity better than other elements, and are malleable and ductile Most of the remaining elements are classified as nonmetals. Their solids have a non-reflective surface, do not conduct heat and electricity well, and are brittle. A few elements are classified as metalloids. Their solids have some characteristics of metals and some of nonmetals. Tro: Chemistry: A Molecular Approach, 2/e

18. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e18 Metals Solids at room temperature, except Hg Reflective surface shiny Conduct heat Conduct electricity Malleable can be shaped Ductile can be drawn or pulled into wires Lose electrons and form cations in reactions About 75% of the elements are metals Left side of table (except H) Tro: Chemistry: A Molecular Approach, 2/e

19. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e19 Nonmetals Found in all three states Poor conductors of heat Poor conductors of electricity Solids are brittle Gain electrons in reactions to become anions Right on the table Sulfur, S(s) Bromine, Br 2 (l) Chlorine, Cl 2 (g) Tro: Chemistry: A Molecular Approach, 2/e

20. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e20 Metalloids Show some properties of metals and some of nonmetals Also known as semiconductors Properties of Silicon shiny conducts electricity does not conduct heat well brittle Tro: Chemistry: A Molecular Approach, 2/e

21. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e21 The Modern Periodic Table Elements with similar chemical and physical properties are in the same column Columns are called Groups or Families designated by a number and letter at top Rows are called Periods Each period shows the pattern of properties repeated in the next period Tro: Chemistry: A Molecular Approach, 2/e

22. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e22Tro: Chemistry: A Molecular Approach, 2/e

23. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e23 Teach the Class: About your assigned elemental family. You must create 3 (max) PowerPoint Slides about your elemental family. In order to receive full credit: Present information in such a manner that your classmates can take notes You must use visuals (Slide 1) Element Examples, Location on Table (Slide 1) Describe physical properties (Slide 2) Describe chemical properties/reactivity and give an explanation for the behavior (Slide 3) Submit to Miss Knick via email 3 questions about your presentation in a word document Cite References on your word document

24. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e24 = Alkali metals = Alkali earth metals = Noble gases = Halogens = Lanthanides = Actinides = Transition metals Tro: Chemistry: A Molecular Approach, 2/e

25. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e lithium sodium potassium rubidium cesium 25 Important Groups – Alkali Metals Group I = Alkali Metals Hydrogen usually placed here, though it doesn ’ t really belong Soft, low melting points, low density Flame tests  Li = red, Na = yellow, K = violet Very reactive, never find uncombined in nature Tro: Chemistry: A Molecular Approach, 2/e

26. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e26 Important Groups – Alkali Earth Metals Group II = Alkali earth metals Harder, higher melting, and denser than alkali metals Mg alloys used as structural materials Flame tests  Ca = red, Sr = red, Ba = green Reactive, but less than corresponding alkali metal Tro: Chemistry: A Molecular Approach, 2/e

27. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e27 Important Groups – Halogens Group 7 = halogens Nonmetals F 2 and Cl 2 gases; Br 2 liquid; I 2 solid All diatomic Very reactive bromine iodine chlorine fluorine astatine Tro: Chemistry: A Molecular Approach, 2/e

28. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e28 Important Groups – Noble Gases Group 8= Noble Gases All gases at room temperature very low melting and boiling points Very unreactive, practically inert Very hard to remove electron from or give electron to Tro: Chemistry: A Molecular Approach, 2/e

29. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e29 Ion Charge and the Periodic Table The charge on an ion can often be determined from an element ’ s position on the Periodic Table Metals always form positively charged cations For many main group metals, the charge = the group number Nonmetals form negatively charged anions For nonmetals, the charge = the group number − 8 Tro: Chemistry: A Molecular Approach, 2/e

30. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e30Tro: Chemistry: A Molecular Approach, 2/e

31. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e Practice – What is the charge on each of the following ions? 31 potassium cation sulfide anion calcium cation bromide anion aluminum cation K + S 2− Ca 2+ Br − Al 3+ Tro: Chemistry: A Molecular Approach, 2/e

32. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e32 Counting Atoms by Moles If we can find the mass of a particular number of atoms, we can use this information to convert the mass of an element sample into the number of atoms in the sample The number of atoms we will use is 6.022 x 10 23, and we call this a mole 1 mole = 6.022 x 10 23 things  like 1 dozen = 12 things Tro: Chemistry: A Molecular Approach, 2/e

33. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e33 Example 2.6: Calculate the number of atoms in 2.45 mol of copper because atoms are small, the large number of atoms makes sense 1 mol = 6.022 x 10 23 atoms 2.45 mol Cu atoms Cu Check: Solution: Conceptual Plan: Relationships: Given: Find: mol Cuatoms Cu Tro: Chemistry: A Molecular Approach, 2/e

34. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e Practice — A silver ring contains 1.1 x 10 22 silver atoms. How many moles of silver are in the ring? 34Tro: Chemistry: A Molecular Approach, 2/e

35. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e Practice — A silver ring contains 1.1 x 10 22 silver atoms. How many moles of silver are in the ring? 35 because the number of atoms given is less than Avogadro’s number, the answer makes sense 1 mol = 6.022 x 10 23 atoms 1.1 x 10 22 atoms Ag moles Ag Check: Solution: Conceptual Plan: Relationships: Given: Find: atoms Agmol Ag Tro: Chemistry: A Molecular Approach, 2/e

36. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e36 Chemical Packages - Moles The number of particles in 1 mole is called Avogadro ’ s Number = 6.0221421 x 10 23 A particle can be anything: atom, molecule, ion, electron, proton, etc. Tro: Chemistry: A Molecular Approach, 2/e

37. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e37 Relationship Between Moles and Mass The mass of one mole of atoms is called the molar mass The molar mass of an element, in grams, is numerically equal to the element ’ s atomic mass, in amu Tro: Chemistry: A Molecular Approach, 2/e

38. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e38 Mole and Mass Relationships 1 mole sulfur 32.06 g 1 mole carbon 12.01 g Tro: Chemistry: A Molecular Approach, 2/e

39. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e39 Example 2.7: Calculate the moles of carbon in 0.0265 g of pencil lead because the given amount is much less than 1 mol C, the number makes sense 1 mol C = 12.01 g 0.0265 g C mol C Check: Solution: Conceptual Plan: Relationships: Given: Find: g Cmol C Tro: Chemistry: A Molecular Approach, 2/e

40. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e Practice — Calculate the moles of sulfur in 57.8 g of sulfur 40Tro: Chemistry: A Molecular Approach, 2/e

41. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e Practice — Calculate the moles of sulfur in 57.8 g of sulfur 41 because the given amount is much less than 1 mol S, the number makes sense 1 mol S = 32.07 g 57.8 g S mol S Check: Solution: Conceptual Plan: Relationships: Given: Find: g Smol S Tro: Chemistry: A Molecular Approach, 2/e

42. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e42 Example 2.8: How many copper atoms are in a penny weighing 3.10 g? because the given amount is much less than 1 mol Cu, the number makes sense 1 mol Cu = 63.55 g, 1 mol = 6.022 x 10 23 3.10 g Cu atoms Cu Check: Solution: Conceptual Plan: Relationships: Given: Find: g Cumol Cuatoms Cu Tro: Chemistry: A Molecular Approach, 2/e

43. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e Practice — How many aluminum atoms are in a can weighing 16.2 g? 43Tro: Chemistry: A Molecular Approach, 2/e

44. Copyright  2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e Practice — How many aluminum atoms are in a can weighing 16.2 g? 44 because the given amount is much less than 1 mol Al, the number makes sense 1 mol Al = 26.98 g, 1 mol = 6.022 x 10 23 16.2 g Al atoms Al Check: Solution: Conceptual Plan: Relationships: Given: Find: g Almol Alatoms Al Tro: Chemistry: A Molecular Approach, 2/e