Ch. 6 The Periodic Table

*Inquiry Activity pg. 154 (R47)*

What do you do with dead chemists? Barium

History • J.W. Dobereiner – 1829 – used properties of elements to

sort them into groups• Dmitri Mendeleev – 1869 – arranged the elements in

order of increasing atomic mass• Henry Moseley – 1913 – in the modern periodic table,

elements are arranged in order of increasing atomic number– Periods – horizontal rows – properties change from L to R but

repeat at each period (periodic law) – 1-7– Groups – vertical columns – similar properties – same # of e’s

in outer energy level – 1-18

Döbereiner’s Triads

NameAtomicMass Name

AtomicMass Name

AtomicMass

Calcium 40Barium 137

Average 88.5

Strontium 87.6

Chlorine 35.5Iodine 127

Average 81.3

Bromine 79.9

Sulfur 32Tellurium 127.5

Average 79.8

Selenium 79.2

Johann Döbereiner ~1817

Döbereiner discovered groups of three related elements which he termed a triad.

Dmitri Mendeleev

Henry Moseley

• Periodic Law

Metals

• Good conductors of heat and electricity• High luster or sheen• All are solid at room temp. except mercury• Ductile – can be drawn into wires• Malleable – can be hammered into thin sheets

w/o breaking• Examples = pg. 159

Nonmetals

• Poor conductors except carbon• Upper right-hand corner of periodic table• Gases or brittle solids at room temp., bromine

is a liquid

Metalloids

• Metallic and nonmetallic properties• Most border the stair-step line• Pg. 160 6.1 assessment

Groups• Alkali metals – group 1 softer than most metals – most

reactive esp. w/ oxygen and water – 1 e- in outer energy level• Alkaline earth metals – group 2 – 2 e- in outer • Halogens – group 17 or 7A – forms salt w/ a metal – 7 e- in

outer• Noble gases – group 18 or 8A – stable – almost nonreactive

(inert) (Representative elements 1-2, 13-17)• Transition metal – presence of e-’s in d orbital – groups 3-12 –

occur in nature uncombined, often form colored compounds – iron triad (steel), coinage metals (copper, silver, gold)

• Inner transition metal – presence of e-’s in f orbital – periods 6 and 7 b/w groups 3 and 4 – lanthanides 58-71, actinides 90-103=radioactive and unstable

• CP 6.1 pg. 167• PP 8-9 pg. 167• 6.2 assessment pg. 167• *Element Research*

Metallic Characteristicmetallic character increases

nonmetallic character increases

met

allic

cha

ract

er in

crea

ses

nonm

etal

lic c

hara

cter

incr

ease

s

Trends in atomic size• Atomic radius = one half of the distance b/w the nuclei

of 2 atoms of the same element when the atoms are joined– Measured in picometers, 1 trillion picometers in 1 meter or

1012

– Atomic size increases from top to bottom w/in a group, decreases from L to R across a period

Ions

• Ions = a charged atom, one that has gained or lost an electron– when sodium loses an electron to form with chlorine,

in order to become stable) it becomes a positive one because it lost a negatively-charged electron• Cation = ion w/ a positive charge

– In the same bonding, chlorine gains the electron sodium lost; thus, it becomes a negative one because it gained a negatively-charged electron• Anion = ion w/ a negative charge

Trends in Ionization Energy

• Ionization energy = the energy required to remove an electron from an atom

• First ionization energy – energy required to remove the 1st electron

• First ionization energy decreases from T to B w/in a group, increases from L to R across a period

• Li, Na, K, relatively easy to remove the first, difficult to remove a second thus they are 1+ ions

• The lower the ionization energy, the easier it is to remove an e- (*Predicting reactivity demo pg 174*)

Shielding• Shielding = The shielding effect describes the decrease in attraction

between an electron and the nucleus in any atom with more than one electron shell.

• When more electrons are involved, each electron (in the n-shell) feels not only the electromagnetic attraction from the positive nucleus, but also repulsion forces from other electrons in shells from 1 to n. This causes the net force on electrons in outer shells to be significantly smaller in magnitude; therefore, these electrons are not as strongly bonded to the nucleus as electrons closer to the nucleus.

• Shielding Demo – 6 volunteers

Trends in Ionic Size• When an atom loses e- it becomes smaller• Cations are smaller than the atoms from

which they form, anions are larger””””

Trends in Electronegativity• Electronegativity = the ability of an atom of an

element to attract electrons when the atom is in a compound

• Values decrease from T to B w/in a group. For representative (1,2, 13-18), values increase from L to R across a period

• Fluorine (4.0) highest, cesium (0.7) lowest

1A 2A 3B 4B 5B 6B 7B 8B 1B 2B 3A 4A 5A 6A 7A 8A1H

2.1

2He

3Li

1.0

4Be1.5

5B

2.0

6C

2.5

7N

3.0

8O

3.5

9F

4.0

10Ne

11Na0.9

12Mg1.2

13Al1.5

14Si

1.8

15P

2.1

16S

2.5

17Cl

3.0

18Ar

19K

0.8

20Ca1.0

21Sc1.3

22Ti

1.5

23V

1.6

24Cr1.6

25Mn1.5

26Fe1.8

27Co1.9

28Ni1.9

29Cu1.9

30Zn1.6

31Ga1.6

32Ge1.8

33As2.0

34Se2.4

35Br2.8

36Kr3.0

37Rb0.8

38Sr1.0

39Y

1.2

40Zr1.4

41Nb1.6

42Mo1.8

43Tc1.9

44Ru2.2

45Rh2.2

46Pd2.2

47Ag1.9

48Cd1.7

49In

1.7

50Sn1.8

51Sb1.9

52Te2.1

53I

2.5

54Xe2.6

55Cs0.7

56Ba0.9

57La1.1

72Hf1.3

73Ta1.5

74W1.7

75Re1.9

76Os2.2

77Ir

2.2

78Pt2.2

79Au2.4

80Hg1.9

81Tl

1.8

82Pb1.9

83Bi

1.9

84Po2.0

85At2.2

86Rn2.4

87Fr

0.7

88Ra0.9

89Ac1.1

104Rf

105Db

106Sg

107Bh

108Hs

109Mt

110Ds

111Uuu

112Uub

113Uut

114Uuq

115Uup

116Uuh

58Ce1.1

59Pr1.1

60Nd1.1

61Pm1.2

62Sm1.2

63Eu1.1

64Gd1.2

65Tb1.2

66Dy1.2

67Ho1.2

68Er1.2

69Tm1.2

70Yb1.2

71Lu1.3

90Th1.3

91Pa1.5

92U

1.7

93Np1.3

94Pu1.3

95Am1.3

96Cm1.3

97Bk1.3

98Cf1.3

99Es1.3

100Fm1.3

101Md

1.3

102No1.5

103Lr

Periodic Table with Electronegativities

Electron affinity

• The Electron affinity of an atom or molecule is defined as the amount of energy released when an electron is added to a neutral atom or molecule to form a negative ion.

Summary of Periodic Trends

Ionic size (cations) Ionic size (anions)decreases decreases

Shielding is constantAtomic radius decreasesIonization energy increasesElectronegativity increasesNuclear charge increases

Nuc

lear

char

ge in

crea

ses

Shie

ldin

g in

crea

ses

Atom

ic ra

dius

incr

ease

sIo

nic s

ize in

crea

ses

Ioni

zatio

n en

ergy

dec

reas

esEl

ectr

oneg

ativi

ty d

ecre

ases

1A

2A 3A 4A 5A 6A 7A

0

• Look at Fig. 6.22 pg. 178• Listing Elements (Ions) Activity – pg. 172• 6.3 section assessment pg. 178• Quick Lab – Periodic trends in ionic radii pg.

175• Work on Packet