Modern inorganic chemistry

120 GROUPS I AND

Table 6.1

SELECTED PROPERTIES OF THE ELEMENTS

Element

Li

Na

K

Rb

Cs

Be

Mg

Ca

Sr

Ba

Atomic

number

3

11

19

37

55

4

12

20

38

56

Outer

electrons

2s^1

3s^1

4s^1

5s^1

6s^1

2s^2

3s^2

4s^2

5s^2

6s^2

Density

(gem'^3 )

0.535

0.971

0.862

1.532

1.90

1.86

1.75

1.55

2.6

3.59

m.p.

(K)

452

370.9

336.5

312

301.5

1553

924

1124

1073

998

b.p.

(K)

1609

1155.9

1035

973

943

3243

1380

1760

1639

1910

Hardness

(Brinell)

0.06

0.07

0.04

0.03

0.02

_

30-40

23

20

._

well marked in Group II but note that beryllium and, to a lesser

extent, magnesium are hard metals, as a result of their small atomic

size; this property, when coupled with their low density, makes

them of some technological importance (p. 124).

Table 6.2

FURTHER PROPERTIES OF THE ELEMENTS OF GROUPS I AND II

Element

Li

Na

K

Rb

Cs

Be

Mg

Ca

Sr

Ba

lonisation

energy*

(kJmol l)

520

496

419

403

376

2657

2187

1735

1613

1467

Metallic

radius

(nm)

0.152

0.186

0.227

0.248

0.263

0.112

0.160

0.197

0.215

0.221

Ionic

radius

(nm)

0.060

0.095

0.133

0.148

0.169

0.031

0.065

0.099

0.113

0.135

Heat of

vaporisation

at 298 K

(kJmor^1 )

152.5

108.6

90.0

85.8

78.8

326

149

177

164

178

Hy drat ion

energy of

gaseous ion

(kJmor^1 )

519

406

322

293

264

2494

1921

1577

1443

1305

(V)

-3.04

• 2.71
  
  
  • 2.92
    -2.93
  
  
  • 2.92
  
  
  • 1.85
  
  
  • 2.37
  
  
  • 2.87
  
  
  
  


• 2.89
  
  
  • 2.91
  
  
  
  

• hor I.i-C's. first lonisation energy; Be Ba, sum ol first and second tonisation energies

A full discussion of the changes in ionisation energy with group
and period position has been given in Chapter 2. These data are
given again in Table 6.2.