Development of thePeriodic Table

John Newlands - Law of Octaves

1864

When arranged in order of atomic mass, every eighth element had similar properties.

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

Modern Periodic Table - Henry Mosley

20th Century

Organized according to atomic number.

an elements position on the periodic table gives indications

of its various physical and chemical properties

Metals, Nonmetals and Metalloids

Metals Nonmetals

In chemical reactions metals tend to lose electrons to nonmetals

Metalloids

metalsgood conductors of heat and electricity

malleable

ductile

lustrous

tend to lose electrons in chemical reactions

nonmetalspoor conductors

brittle

tend to gain electrons in chemical reactions

Specific Groups

Main groupsgroup numbers identified by suffix A

Main group metalsAlkali metals Alkaline earth metals

NonmetalsHalogens Noble gases

transition metalsLanthanidesActinides

Periodic Classification ofthe Elements

Valence Electrons

The outer electrons of an atom, which arethose involved in chemical bonding, are often called the valence electrons.

Elements in the same group of the periodictable have analogous valence-electron figurations.

Group 8A

1

2

3

4

6

5

He

Ne

Ar

Kr

Rn

Xe

1s2

[He]2s22p6

[Ne]3s23p6

[Ar]3d104s24p6

[Xe]5d104f146s26p6

[Kr]4d105s25p6

noble gases

Group 1A

1234

65

7

HLiNaK

CsRb

Fr

1s1

[He]2s1

[Ne]3s1

[Ar]4s1

[Xe]6s1

[Kr]5s1

[Rn]7s1

alkali metals

Group 2A

234

65

7

BeMgCa

BaSr

Ra

[He]2s2

[Ne]3s2

[Ar]4s2

[Xe]6s2

[Kr]5s2

[Rn]7s2

Alkaline earth metals

Group 7A

234

65

FClBr

AtI

2s2 2p5

3s2 3p5

4s2 4p5

6s2 6p5

5s2 5p5

halogens

Ions

When electrons are removed from or added to a neutral atom or molecule, a

charged particle called an ion is formed.

Ions

Positively charged ions are calledcations

Negatively charged ions are calledanions

Ions

positively charged: cations

negatively charged: anions

most common type is metal cationNa+, Ca2+, Al3+, Fe2+, Fe3+

most common type is nonmetal anionCl–, O2–

the chemical behavior of an atom

depends on how hard an atom holds on to its electrons

Metals Nonmetals

In chemical reactions metals tend to lose electrons to nonmetals

Na: 11 protons; 11 electrons

Atoms vs Ions

Cl: 17 protons; 17 electrons

Na 11

2p2s

1s

3p3s

1s2 2s22p6 3s1

[Ne] 3s1

Cl 17 1s2 2s22p6 3s23p5

[Ne] 3s23p5

3p3s

2p2s

1s

Na

17 P+

11 P+

Cl

2 e- 8 e-

7 e-

2 e -

8 e-

1 e-1st2nd

3rd

1st2nd

3rd

Na

17 P+

11 P+

Cl

1s

2s 2p

3p3s

1s2s 2p

3p3s

3d

3d

Na

17 P+

11 P+

Cl

1s

2s 2p

3p3s

1s2s 2p

3p3s

3d

3d

Na

17 P+

11 P+

Cl

1s

2s 2p

1s2s 2p

3p3s

+

3d

Na

17 P+

11 P+

Cl

2 e- 8 e-

8 e-

2 e -

8 e-

+

Cl–: 17 protons; 18 electrons

–

Na+: 11 protons; 10 electrons

+

electrostatic attraction between oppositely charged ions

–+

Atoms vs Ions

Oxidation state

signifies the number of charges the atom would have in a molecule ( or an ionic compound ) if electrons were transferred completely.

Electron Configurations of Cations and Anions

Element AtomSodium Na [Ne]3s1

Magnesium Mg [Ne]3s2

Aluminum Al [Ne]3s23p1

IonNa+ [Ne]Mg2+ [Ne]Al3+ [Ne]

Isoelectronic species have the same number of electrons.

Electron Configurations of Cations and AnionsElement AtomHydrogen H 1s1 H–

Fluorine F 1s2 2s2 2p5 F–

Oxygen O 1s2 2s2 2p4 O2–

Ion 1s2

1s22s22p6

1s22s22p6

1s22s22p6Nitrogen N 1s2 2s2 2p3 N3–

Isoelectronic species have the same number of electrons.