Chapter 6Chapter 6

Periodic TablePeriodic Table

HistoryHistory

A. John NewlandsA. John Newlands1. Law of octaves1. Law of octaves2. Properties repeat every 8 elements 2. Properties repeat every 8 elements when when arranged by atomic massarranged by atomic mass

B. Dmitri MendeleevB. Dmitri Mendeleev1. Published 11. Published 1stst periodic table periodic table2. Arranged elements in order of 2. Arranged elements in order of increasing increasing atomic massatomic mass

Dobereiner’s TriadsDobereiner’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 Dobereiner ~1817

Dobereiner discovered groups of three related elements which he termed a triad.Smoot, Price, Smith, Chemistry A Modern Course 1987, page 161

Newland’s Law of Newland’s Law of OctavesOctaves

Newland’s Law of Octaves

1

LiNaK

John Newlands ~1863

Smoot, Price, Smith, Chemistry A Modern Course 1987, page 161

2

BeMg

3

BAl

4

CSi

5

NP

6

OS

7

FCl

C. Henry Mosley – arranged elements C. Henry Mosley – arranged elements in order of increasing atomic in order of increasing atomic number – modern periodic tablenumber – modern periodic table

D. Periodic Law – the properties of D. Periodic Law – the properties of the elements are a periodic the elements are a periodic function of the atomic numberfunction of the atomic number

Modern Periodic TableModern Periodic Table Henry G.J. Moseley Henry G.J. Moseley Determined the atomic Determined the atomic

numbers of elements numbers of elements from their from their XX-ray -ray spectra (1914)spectra (1914)

Arranged elements by Arranged elements by increasing atomic increasing atomic numbernumber

Killed in WW I at age Killed in WW I at age 2828(Battle of Gallipoli in (Battle of Gallipoli in Turkey)Turkey)

1887 - 1915

E. E. Grouping of ElementsGrouping of Elements

1. Groups or families – elements in same 1. Groups or families – elements in same

vertical column have similar propertiesvertical column have similar properties

2. Periods – elements in the same 2. Periods – elements in the same horizontal horizontal

rowrow

3. Representative elements – Groups 3. Representative elements – Groups

designated with an A on periodic table designated with an A on periodic table – –

wide range ofwide range of properties properties

4. Transition elements Group 4. Transition elements Group designated with a Bdesignated with a B

5. Metals – elements to the left of the 5. Metals – elements to the left of the heavy stairstep lineheavy stairstep line

6. Nonmetals – elements to the right 6. Nonmetals – elements to the right of the heavy stairstep lineof the heavy stairstep line

7. Metalloids – elements adjacent to 7. Metalloids – elements adjacent to the heavy stairstep line except for the heavy stairstep line except for aluminum which is a metalaluminum which is a metal

8. Alkali metals – group 1A8. Alkali metals – group 1A

9. Alkaline earth metals – group 2A9. Alkaline earth metals – group 2A

10. Noble gases – group 8A10. Noble gases – group 8A

11. Halogens – group 7A11. Halogens – group 7A

Groups of ElementsGroups of Elements

Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 367

N

7

P

15

As

33

Sb

51

Bi

83

O

8

S

16

Se

34

Te

52

Po

84

F

9

Cl

17

Br

35

I

53

At

85

He

2

Ne

10

Ar

18

Kr

36

Xe

54

Rn

86

Li

3

Na

11

K

19

Rb

37

Cs

55

Fr

87

Be

4

Ca

20

Sr

38

Ba

56

Ra

88

Mg

12

1

2

1

2

15

16

17

18

Alkali metals

Alkaline earth metals

Nitrogen family

Oxygen family

Halogens

Noble gases

13 14 15 16 17

18

Classification of the Classification of the ElementsElements

A. Organizing by electron configurationA. Organizing by electron configuration

1. Atoms in the same group have similar 1. Atoms in the same group have similar

chemical properties because they chemical properties because they have the have the

same number of valence electrons – same number of valence electrons –

electron dot diagrams are the sameelectron dot diagrams are the same

2. Elements in the same period have 2. Elements in the same period have valence valence

electrons in the same energy levelelectrons in the same energy level

B. s,p,d,f Blocks – indicates sublevel B. s,p,d,f Blocks – indicates sublevel to which electrons are being addedto which electrons are being added

Periodic TrendsPeriodic Trends

A. Atomic RadiusA. Atomic Radius

1. In a period radius decreases left to right 1. In a period radius decreases left to right

because of increasing positive charge in because of increasing positive charge in

nucleusnucleus

2. In a family, radius increases top to bottom 2. In a family, radius increases top to bottom

because electrons are being added to because electrons are being added to higherhigher

energy levels and more electrons between energy levels and more electrons between valence valence

electrons and nucleus result in “shielding electrons and nucleus result in “shielding effect”effect”

B. Ionic RadiusB. Ionic Radius

1. Positive ions are smaller than 1. Positive ions are smaller than the neutral the neutral

atomsatoms

2. Negative ions are larger than 2. Negative ions are larger than the neutral the neutral

atomsatoms

C. Ionization Energy – the energy required to C. Ionization Energy – the energy required to remove an outer electron from a gaseous remove an outer electron from a gaseous atomatom1. In a period, ionization energy generally 1. In a period, ionization energy generally increases left to right – nucleus has increases left to right – nucleus has higherhigher positive charge and electrons are closer positive charge and electrons are closer toto nucleusnucleus2. In a family, ionization energy decreases 2. In a family, ionization energy decreases top top to bottom because electrons are further to bottom because electrons are further

from the nucleus and because of the from the nucleus and because of the shielding effectshielding effect

3. Octet rule – atoms tend to gain, 3. Octet rule – atoms tend to gain, lose or lose or

share electrons to acquire a full set share electrons to acquire a full set of 8 of 8

valence electronsvalence electrons

D. Electronegativity – the relative ability D. Electronegativity – the relative ability of an of an

atom to attract electrons in a chemical atom to attract electrons in a chemical bondbond

1. Increases in a period left to right1. Increases in a period left to right

2. Decreases in a family top to bottom2. Decreases in a family top to bottom