Physical Chemistry Third Edition

816 19 The Electronic States of Atoms. III. Higher-Order Approximations

that the data were faked.^32 Another claim for element 116 has been made.^33 More

recently, a plausible claim for production of element 118 has been made. Three atoms

of element 118 were produced by bombarding californium 249 with calcium 48. The

three nuclei survived for 0.9 ms on the average.^34

The correlation between position in the periodic table and chemical properties was

explained by Niels Bohr, who also introduced the form of the chart with 18 columns.

It has also been claimed that C. R. Bury should be given credit as the co-discoverer

of this correlation.^35 The similarity of chemical properties of the elements in a given

column corresponds to the similarity of their electron configurations in the outermost

shell, which is called thevalence shell. For example, the alkali metals (lithium, sodium,

potassium, etc.) easily lose one electron because these elements have only one electron

in the valence shell. The halogens (fluorine, chlorine, bromine, iodine, and astatine)

have seven electrons in the valence shell, and tend to gain one electron. The eight

columns of representative elements occur as two columns on the left and six columns

on the right, corresponding to the two spin orbitals of anssubshell and the six spin

orbitals of apsubshell. The transition elements occur in ten columns, corresponding

to the ten spin orbitals of adsubshell, and the inner transitions elements occur in 14

columns, corresponding to the 14 spin orbitals of anfsubshell.

Various properties correlate with position in the periodic table. Figure 19.7 shows the

first ionization potential of the elements as a function of atomic number. The ionization

potential generally increases from left to right across a row of the periodic table, and

decreases from top to bottom in a column. The increase from left to right is attributed

to the corresponding increase in the effective nuclear charge. The general decrease

from top to bottom is attributed to the fact that as one moves down the column the

valence shell is farther from the nucleus, lessening its attraction for the electrons in the

valence shell. The corresponding increase in the nuclear charge is compensated for by

increased shielding by the inner electrons.

Several elements, including beryllium, nitrogen, magnesium, phosphorus, zinc, and

mercury, have higher ionization potentials than both of their immediate neighbors in a

2500

He

Ne

Na K

Ar

Kr

Xe

Zn

Rb Cs

Hg Rn

2000

1500

1000

500

0

0 10203040

Atomic number

First ionization energy/kJ mol

–1

50 60 70 80 90

N

Be

Mg

P

Li

H

Figure 19.7 First Ionization Potentials of the Elements.

(^32) V. Ninov,et al.,Phys. Rev. Letters, 83 , 1104 (1999), errata inPhys. Rev. Letters, 89 , 39901 (2002).
(^33) Yu. Ts. Oganessian,et al.,Phys. Rev. C., 63 , 11301 (2002).
(^34) Yu. Ts. Oganessian,et al.,Phys. Rev. C., 74 , 44602 (2006).
(^35) C. Truesdell,Archives for the History of Exact Sciences, 41 , 185 (1990).