Modern inorganic chemistry

12 The noble gases

(Helium neon, argon, krypton, xenon, radon)

These elements were unknown when Mendeleef constructed his

periodic table, and are often said to constitute 'Group O\ How

ever, a more logical classification would be in "Group VIIF.

PHYSICAL PROPERTIES

These are given in Table 12.1. The following are to be noted:

1. The increase in atomic radius (in this group, the actual radius
   of the free atom).

Table 12.1

SELECTED PROPERTIES OF THE ELEMENTS

ElementP. Atomic ,

number

He 2

Ne 10

Ar 18

Kr 36

Xe 54

Rn 86

* van der Waals radius.

t Pressure lOOatm.

Outer

electrons

is^2

2s^2 2p^6

3s^2 3p^6

(^4) s^2 4p^6
5s^2 5p^6
6s^2 6p^6
Atomic
radius*
(nm)
0.099
0.160
0.192
0.197
0.217
—
m.p.
(K)
4f
25
84
116
161
202
b.p.
(K)
4
27
87
120
165
211
1st ionisation
energy
(kJmor^1 )
2372
2080
1520
1351
1169
1037
353