1869 Mendeleev: method of organizing the elements according to both their masses and their properties. The Old Table

Transcription

1 The Periodic Table

2 1869 Mendeleev: method of organizing the elements according to both their masses and their properties. The Old Table

3 Vertical Columns: Elements arranged in groups each group shares similar properties. Horizontal Rows: Elements are arranged in periods

4 Mendeleev s table showed gaps, indicating missing elements (not discovered yet). Why was this important? The location of missing elements allowed their chemical and physical properties to be predicted.

5 The Modern Periodic Table Elements arranged by atomic number (not mass) (eg. K heavier than Ar..due to isotopes)

6 Periodic Law: The properties of the elements recur along the rows (i.e. an element has similar properties to the one below or above it)

7 Division in the Periodic Table Period: all elements in a given row of the periodic table. Group or family: all elements in a given column of the periodic table. Rows = Periods Columns = Groups or families

8 Particular groups, rows and blocks of elements Alkali metals group 1 (except hydrogen) Alkaline earth metals group 2 Transition metals block d Representative elements main group elements, s and p blocks Halogens 2 nd last group (starts with F) Noble gases last group (these elements have full valence orbitals) Lanthanides row with atomic # 57 # 71 Actinides below Lanthanides, atomic # 89 #103

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10 We can also divide P.T. into: Metals, Non-metals and Semiconductors Elements become more metallic from _right to left across the periodic table and from top to _bottom of a group.

11 Properties of METALS: shiny. opaque. good conductors of heat and electricity. usually flexible when in sheet form. malleable and ductile. solid at room temp. (except of Hg)

12 Properties of NON-METALS: gas, liquid, or brittle solids at room temp. poor conductors of heat and electricity. solids are not shiny

13 2 types of Non- metals: 1. Low electrical conductivities. 2. Moderate electrical conductivities. Some elements DO share properties of metals and non-metals

14 Semiconductors (metalloids or moderate electrical conductivities ) non-metal. electrical conductivity increases when T eg) B, Si, Ge, As, Sb, Te, At

15 Now You Try!! Do the following questions with your partner orally (5 min) Homework p. 164 #35-39

16 Electrostatic Trends in P.T. from right to left and top to bottom of the Periodic Table elements become more metallic atomic radius increases from left to right and bottom to top of the P.T electron affinity increases ionization energy increases Electronegativity increases

17 Electronegativity Electronegativity

18 Ionization Energy (I.E.) I.E. is the energy required to remove one or more electrons from a neutral atom in the gas phase 1st I.E.: The energy required to remove the 1 st valence electron 2nd I.E.: The energy required to remove the 2 nd valence electron 3rd I.E.: The energy required to remove the 3 rd valence electron 4th I.E.: The energy required to remove the 4 th valence electron eg) 1st IE: Rb(g) Rb + (g) + e- ( Hº = 400 kj/mol) 2nd IE: Rb+ (g) Rb 2+ (g) + e- ( Hº = 580 kj/mol) 3rd IE: Rb2+(g) Rb 3+ (g) + e- ( Hº = 600 kj/mol)

19 Explaining I.E. s 1. The positively charged nucleus attracts the electrons therefore the 1 st I.E. of He is approx twice the 1 st I.E. of H. This is because H has 1 proton and He has 2. Therefore the IE increases as nucleus size increases

20 2. Electrons in higher n feel less attraction to the nucleus because electrons in smaller n shield/block the attractive force of nucleus electrons in higher n are easier to remove. Therefore IE decrease as n increases.

21 eg) Which has higher I.E.? a. Na or Mg b. Mg or Al c. F or Cl

22 Now You Try Do these questions p. 168 #48, 49 and 51

23 Electron Affinity (E.A.) E.A. is the E that occurs when a neutral atom in the gas phase gains an electron. (or how much a neutral atom wants an electron) eg) F (g) + e - F - (g) E.A. increases as atom size decreases because the elecrons added is nearer the nucleus (lower n) the electrons repelled by fewer other electrons

24 Atomic radius: distance from center of nucleus to outermost electron 1) Moving down a group, n increases orbital size increases atomic radius increases Atomic Radius 2) Moving left to right across a period Number of protons increases orbital size decreases atomic radius decreases

25 eg) Which is smaller? a) K or Ca b) Rb or Sb c) Sn or Pb d) O or S

26 Now you try!! Do these questions in your work book P # 53(a,b,c,d,f) 54, 55(a,b,c,d,f) 56

27 Electronegativity (E.N.) E.N. is the tendency of the atom to attract e -s from a neighbouring atom or how strongly an atom pulls on nearby electrons. E.N. increases as you move from left to right ( ) and from bottom to top( ) of the P.T.

28 Atoms with high Electronegativity strongly attracts e -s from nearby atoms strongly attracts its own valence e -s vice versa also true.. Atoms with low E.N. have little attraction for electrons from a nearby atom and for its own electrons

29 eg) Li and F Li has low E.N. F has high E.N. \ \ gives away an e- easily) attracts e- strongly) If F and Li are near F takes an e - from Li

30 In the P.T: Moving: Atom s properties are affected by: Down a family Increasing atom size and increasing distance between nucleus and valence e -s Across a period. Differing valence, nuclear charge, and charge on species

31 Chemical Reactivity How likely or strongly an atom will react with other substances. This is determined by how easily electrons can be removed (ionization energy) and how badly they want to take other atom's electrons (electronegativity).

32 Metals Period - reactivity decreases as you go from left to right across a period. Group - reactivity increases as you go down a group Why? The farther to the left and down the periodic chart you go, the easier it is for electrons to be given or taken away, resulting in higher reactivity.

33 Non-metals Period - reactivity increases as you go from the left to the right across a period Group - reactivity decreases as you go down the group. Why? The farther right and up you go on the periodic table, the higher the electronegativity, resulting in a more vigorous exchange of electrons.

34 Exception Nobel gases are non reactive

35 Now you try!! Do these questions in your work book p. 173 #58 61