Development of the Periodic Table

Transcription

1 Development of the Periodic Table

2 John Newlands - Law of Octaves 1864 When arranged in order of atomic mass, every eighth element had similar properties.

3 Dimitri Mendeleev / Lothar Meyer 1869 organized elements arranged according to atomic mass. Mendeleev showed how useful the table could be in predicting the existence and properties of yet unknown elements

4 Dmitri Mendeleev and Lothar Meyer independently came to the same conclusion about how elements should be grouped Pearson Education, Inc. Periodic Properties of the Elements

5 Modern Periodic Table - Henry Mosley 20th Century Organized according to atomic number.

6 an elements position on the periodic table gives indications of its various physical and chemical properties

7 Metals, Nonmetals and Metalloids

8 Metals Metalloids Nonmetals In chemical reactions metals tend to lose electrons to nonmetals

9 Properties of Metal, Nonmetals, and Metalloids 2012 Pearson Education, Inc. Periodic Properties of the Elements

10 Metals versus Nonmetals Metals tend to form cations. Nonmetals tend to form anions Pearson Education, Inc. Periodic Properties of the Elements

11 Metals Metals tend to be lustrous, malleable, ductile, and good conductors of heat and electricity Pearson Education, Inc. Periodic Properties of the Elements

12 Metals Compounds formed between metals and nonmetals tend to be ionic. Metal oxides tend to be basic Pearson Education, Inc. Periodic Properties of the Elements

13 Nonmetals Nonmetals are dull, brittle substances that are poor conductors of heat and electricity. They tend to gain electrons in reactions with metals to acquire a noble-gas configuration Pearson Education, Inc. Periodic Properties of the Elements

14 Nonmetals Substances containing only nonmetals are molecular compounds. Most nonmetal oxides are acidic Pearson Education, Inc. Periodic Properties of the Elements

15 Metalloids Metalloids have some characteristics of metals and some of nonmetals. For instance, silicon looks shiny, but is brittle and a fairly poor conductor Pearson Education, Inc. Periodic Properties of the Elements

16 metals good conductors of heat and electricity malleable nonmetals poor conductors brittle ductile lustrous tend to lose electrons in chemical reactions tend to gain electrons in chemical reactions

17 Specific Groups

18 Main groups group numbers identified by suffix A

19 Main group metals Alkali metals Alkaline earth metals

20 Nonmetals Halogens Noble gases

21 Actinides transition metals Lanthanides

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23 Periodic Classification of the Elements

24 Valence Electrons The outer electrons of an atom, which are those involved in chemical bonding, are often called the valence electrons. Elements in the same group of the periodic table have analogous valence-electron figurations.

25 Group 8A noble gases He Ne Ar Kr Xe Rn 1s 2 [He]2s 2 2p 6 [Ne]3s 2 3p 6 [Ar]3d 10 4s 2 4p 6 [Kr]4d 10 5s 2 5p 6 [Xe]5d 10 4f 14 6s 2 6p 6

26 Group 1A alkali metals H Li Na K Rb Cs Fr 1s 1 [He]2s 1 [Ne]3s 1 [Ar]4s 1 [Kr]5s 1 [Xe]6s 1 [Rn]7s 1

27 Group 2A Alkaline earth metals Be Mg Ca Sr Ba Ra [He]2s 2 [Ne]3s 2 [Ar]4s 2 [Kr]5s 2 [Xe]6s 2 [Rn]7s 2

28 Group 7A halogens F Cl Br I At 2s 2 2p 5 3s 2 3p 5 4s 2 4p 5 5s 2 5p 5 6s 2 6p 5

29 Ions

30 Ions When electrons are removed from or added to a neutral atom or molecule, a charged particle called an ion is formed.

31 Positively charged ions are called cations Negatively charged ions are called anions

32 Ions positively charged: cations most common type is metal cation Na +, Ca 2+, Al 3+, Fe 2+, Fe 3+ negatively charged: anions most common type is nonmetal anion Cl, O 2

33 the chemical behavior of an atom depends on how hard an atom holds on to its electrons

34 Effective Nuclear Charge In a many-electron atom, electrons are both attracted to the nucleus and repelled by other electrons. The nuclear charge that an electron experiences depends on both factors Pearson Education, Inc. Periodic Properties of the Elements

35 Metals Nonmetals In chemical reactions metals tend to lose electrons to nonmetals

36 Atoms vs Ions Na: 11 protons; 11 electrons Cl: 17 protons; 17 electrons

37 Electron Configurations of Cations and Anions Element Atom Ion Sodium Na [Ne]3s 1 Magnesium Mg [Ne]3s 2 Aluminum Al [Ne]3s 2 3p 1 Na + [Ne] Mg 2+ [Ne] Al 3+ [Ne] Isoelectronic species have the same number of electrons.

38 Electron Configurations of Cations and Anions Element Atom Ion Hydrogen H 1s 1 H Fluorine F 1s 2 2s 2 2p 5 F Oxygen O 1s 2 2s 2 2p 4 O 2 Nitrogen N 1s 2 2s 2 2p 3 N 3 1s 2 1s 2 2s 2 2p 6 1s 2 2s 2 2p 6 1s 2 2s 2 2p 6 Isoelectronic species have the same number of electrons.

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40 Alkali Metals Alkali metals are soft, metallic solids. The name comes from the Arabic word for ashes Pearson Education, Inc. Periodic Properties of the Elements

41 Alkali Metals They are found only in compounds in nature, not in their elemental forms. They have low densities and melting points. They also have low ionization energies Pearson Education, Inc. Periodic Properties of the Elements

42 Alkali Metals Their reactions with water are famously exothermic Pearson Education, Inc. Periodic Properties of the Elements

43 Alkali Metals Alkali metals (except Li) react with oxygen to form peroxides. K, Rb, and Cs also form superoxides: K + O 2 KO 2 They produce bright colors when placed in a flame Pearson Education, Inc. Periodic Properties of the Elements

44 Alkaline Earth Metals Alkaline earth metals have higher densities and melting points than alkali metals. Their ionization energies are low, but not as low as those of alkali metals Pearson Education, Inc. Periodic Properties of the Elements

45 Alkaline Earth Metals Beryllium does not react with water, and magnesium reacts only with steam, but the other alkaline earth metals react readily with water. Reactivity tends to increase as you go down the group Pearson Education, Inc. Periodic Properties of the Elements

46 Group 6A Oxygen, sulfur, and selenium are nonmetals. Tellurium is a metalloid. The radioactive polonium is a metal Pearson Education, Inc. Periodic Properties of the Elements

47 Sulfur Sulfur is a weaker oxidizer than oxygen. The most stable allotrope is S 8, a ringed molecule Pearson Education, Inc. Periodic Properties of the Elements

48 Group VIIA: Halogens The halogens are prototypical nonmetals. The name comes from the Greek words halos and gennao: salt formers Pearson Education, Inc. Periodic Properties of the Elements

49 Group VIIA: Halogens They have large, negative electron affinities. Therefore, they tend to oxidize other elements easily. They react directly with metals to form metal halides. Chlorine is added to water supplies to serve as a disinfectant Pearson Education, Inc. Periodic Properties of the Elements

50 Group VIIIA: Noble Gases The noble gases have astronomical ionization energies. Their electron affinities are positive. Therefore, they are relatively unreactive. They are found as monatomic gases Pearson Education, Inc. Periodic Properties of the Elements

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