How are most library books classified? Why is such a classification system useful?

Transcription

1 How are most library books classified? Why is such a classification system useful?

2 Chapter 6 and 7 The Periodic Table and Periodic Law Harry Potter Sings the Element Song Jim Lehrer The Real Periodic Table Song

3 Lavoisier Acid making sulfur phosphorous carbon Gas like light heat oxygen Azote (nitrogen) hydrogen

4 Lavoisier Metallic Cobalt, mercury, tin Copper, nickel, iron Gold, lead, silver, zinc Manganese, tungsten (platina) platinum Earthy Lime (calcium hydroxide) Magnesia (magnesium oxide) Barytes (barium sulphate) Argilla (Aluminum oxide) Silex (silicon dioxide)

5 I. Development of the Modern Periodic Table 6.1 pg A. Lavoisier 1790 s 1. Compiled a list of 23 elements known at the time s: changes in the world 3. Electricity used to break compounds, spectrometer, industrial revolution 4. Tripled Lavoisier s number of elements chemists agreed on atomic masses

6 B. John Newland Proposed an organization scheme 2. Arranged by increasing atomic mass 3. The elements properties repeated every eighth element 4. The law of octaves. Musical Analogy

7 B. John Newland

8 C. Meyer, Mendeleev, & Moseley 1. Meyer & Mendeleev each demonstrated connections between atomic mass and elemental properties. 2. Mendeleev published first and showed the connections usefulness 3. Mendeleev predicted the existence and properties of undiscovered elements. 4. He left blanks for undiscovered elements Can you find the errors in his system?

9 C. Meyer, Mendeleev, & Moseley

10 Mendeleev s First Periodic Table "...if all the elements be arranged in order of their atomic weights a periodic repetition of properties is obtained." - Mendeleev

11 5. Henry Moseley (1913): British chemist - discoveries resulted in a more accurate positioning of elements by determination of atomic numbers. (Tragically for the development of science, Moseley was killed in action at Gallipoli in 1915).

12 5. Moseley (continued) 5. When atoms were arranged according to increasing atomic number, the few problems with Mendeleev's periodic table had disappeared. Because of Moseley's work, the modern periodic table is based on the atomic numbers of the elements 6. Periodic Law: There is a periodic repetition of the chemical and physical properties of the elements when they are arranged by increasing atomic number.

13 5. Moseley

14 BCC History of the Periodic Table

15 II. The Modern Periodic Table

16 II. The Modern Periodic Table A. Columns on the periodic table are called groups or families. Atomic number increases as you move down on the periodic table. Each group is numbered one though eight, followed by the letter A or B. What group is Chlorine in? VIIA

17 II. The Modern Periodic Table B. The rows on the periodic table are called periods. Each row on periodic table (except the first) begins with a metal and ends with a noble gas. Beginning with hydrogen in period 1 there are a total of seven periods. In between, the properties of the elements change in an orderly progression from left to right. The pattern in properties repeats after group VIIIA (18).

18 II. The Modern Periodic Table C. Why does the first period on the periodic table only have two elements? Only two electrons can occupy the first energy level in an atom. The third electron in lithium must be at a higher energy level. Lithium is the first element in Group IA and in Period 2.

19 II. The Modern Periodic Table D. The groups designated with an A (IA through VIIIA) are often referred to as the main group or representative elements because they possess a wide range of chemical and physical properties. The groups designated with a B (IB through VIIIB) are referred to as the transition elements.

20 II. The Modern Periodic Table Vanadium a transition element.

21 III. Classification of the Elements A.Valence Electrons 1. electrons in the highest principal energy level 2. What would group IA look like? 1s 1, 2s Atoms in the same group have similar chemical properties because they have the same number of valence electrons. B. The s-, p-, d- and f- block elements

22 III. Classification of the Elements

23 III. Classification of the Elements A. Metals are elements that have luster, conduct heat and electricity, and usually bend without breaking, and are solid at room temperature. With the exception of tin, lead, and bismuth, metals have one, two, or three valence electrons.

24 The metals

25 III. Classification of the Elements Metals are to the left of the heavy stair-step line that zigzags down from Boron (B, in column IIIA) to astatine (At) at the bottom of group VIIA (hydrogen is the exception). Alkali metals group IA, the most reactive of all metals. They react with water to form alkaline solutions.

26 Alkali metals

27 III. Classification of the Elements Alkaline earth metals group IIA. These elements form compounds with oxygen, called oxides. All transition elements are metals.

28 III. Classification of the Elements All transition elements are metals.

29 III. Classification of the Elements Inner transition metals are know as lanthanide and actinide series and are located along the bottom of the periodic table. Because of their natural abundance on Earth is less than 0.01 percent, the lanthanides are sometimes called the rare earth elements. All of the lanthanides have similar properties.

30 III. Classification of the Elements All of the actinides are radioactive, and none beyond uranium (92) occur in nature.

31 Meet Dr. Glenn Seaborg

32 III. Classification of the Elements B. Nonmetals are elements that are generally gases or brittle, dull-looking solids. They are poor conductors of heat and electricity. The only liquid nonmetal at room temperature is bromine (Br). The highly reactive group VIIA is the halogens, salt formers. The extremely un-reactive group is the noble gases. The nonmetals oxygen and nitrogen make up 99 percent of Earth s atmosphere.

33 III. Classification of the Elements Carbon, another nonmetal, is found in more compounds than all the other elements combined. Their melting points tend to be lower than those of metals.

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35 III. Classification of the Elements C. Metalloids or semimetals. Metalloids are elements with physical and chemical properties of both metals and nonmetals. Silicon and germanium are tow of the most important metalloids as they are used extensively in computer chips and solar cells.

36 III. Classification of the Elements Some metalloids such as silicon, germanium (Ge), and arsenic (As) are semiconductors.

37 III. Classification of the Elements A semiconductor is an element that does not conduct electricity as well as a metal, but does conduct slightly better than a nonmetal. The ability of a semiconductor to conduct an electrical current can be increased by adding a small amount of certain other elements.

38 III. Classification of the Elements Silicon s semi conducting properties made the computer revolution possible. Your television, computer, handheld electronic games, and calculator are electrical devices that depend on silicon semiconductors.

39 III. Classification of the Elements All have miniature electrical circuits that use silicon s properties as a semiconductor. You learned that metals generally are good conductors of electricity, nonmetals are poor conductors, and semiconductors fall in between the two extremes.

40 III. Classification of the Elements The ability of a semiconductor to conduct an electrical current can be increased by adding a small amount of certain other elements. Silicon s semi conducting properties made the computer revolution possible. Your television, computer, handheld electronic games, and calculator are electrical devices that depend on silicon semiconductors.

41 III. semiconductors

42 What clues does the arrangement of the football players on the field give about the functions of their positions?

43 What characteristics does a football player have based on the position played?

44 V. Periodic Trends 6.3 pgs A. Atomic Size or Radius 1. How closely an atom lies to a neighboring atom. 2. Metals half the distance between two adjacent atoms in a crystal 3. Nonmetal determined from a diatomic molecule of an element

45 Time out! What s a diatomic element?

46 Time out! What s a diatomic element? an element that when not chemically bonded with any other elements, will form a molecule having two atoms of the element. N 2, H 2, F 2 Mr. Brinklehoff BrINClHOF gases

47 A. Atomic Radii - trend (cont.) Size increases going across right to left. (Across same energy level, but add protons and the pull of nucleus is greater and pulls electrons closer.) Size increases going down a group. Electrons are at progressively higher levels, and shielding effect is increasing.

48 A. Atomic Radii (continued) Shielding Effect lots of inner electrons shield or protect the outer electrons from the pull of the positive nucleus. What happens to shielding effect as you go down the periodic table? increases What happens to shielding effect as you go across the periodic table? Stays the same

49 B. Ionic Radius Positive ions are always smaller than neutral atoms Negative ions are always larger than neutral atoms because their nuclear attraction is less

50 Going down a group both anions and cations get bigger Going across: + decrease, - increase Smaller Larger

51 Atomic and ionic radii trends

52 C. Ionization Energy Energy required to remove an electron from a gaseous atom. Think of ionization energy as an indication of how strongly an atom s nucleus holds onto its valence electrons. Bigger your ionization energy the harder it is to rip an electron away. How easy is it to become an ion?

53 Ionization energy

54 I.E. increases going up (harder to pull off outer electrons when atoms are smaller) I.E. increases going across (harder to pull off electrons because of nuclear attraction is hanging onto them. Metals have lower I.E., nonmetals have high I.E. High High

55 Successive ionization energies

56 D. Electronegativity indicates the relative ability of an atom to attract electrons in a chemical bond hogs electrons The bigger the electronegativity the bigger the hog

57 Polar Covalent Bonds Though atoms often form compounds by sharing electrons, the electrons are not always shared equally. Fluorine pulls harder on the electrons it shares with hydrogen than hydrogen does. Therefore, the fluorine end of the molecule has more electron density than the hydrogen end.

58 Electronegativity Electronegativity is the ability of atoms in a molecule to attract electrons to themselves. On the periodic chart, electronegativity increases as you go from left to right across a row. from the bottom to the top of a column.

59 D. Electronegativity (continued) moving across, electronegativity increases moving up electronegativity increases high highest

60 Video Electronegativity

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62 Following Slides not covered in chapter 6 Glencoe

63 E. Electron Affinity Electron Grabbiness or how easy it is for an atom to gain electrons (make a negative ion = anion) (-) negative = energy released (+) positive = energy absorbed

64 Electron Affinity

65 E. Electron Affinity (continued) Generally decreases going down a group because atomic size increases Increases going across because atoms are smaller and nucleus charge increases

66 F. Melting Points metallic side decreases as you go down non-metals- increase going down melting pt of gases are very low (-100 C)

67 G. Metallic Character increase to left and down least metallic most metallic

68 Metallic Character

69 H. Chemical Activity metals increase going down, most active? Cs non metals decreases going down, most active? F

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