Periodic trends in first ionization energies

Ii generally increases as we move across a period. The alkali metals show the lowest ionization energy in each period, and the noble gases show the highest. There are slight irregularities in this trend that we will discuss shortly. 

fr generally decreases as we move down any column in the periodic table. For example, the ionization energies of the noble gases follow the order He Ne Ar Kr Xe. 

A FIGURE 7.9 Trends in first ionization energies of the eiements. 

Explain why it is easier to remove a 2p electron from an oxygen atom than from a nitrogen atom. 

Referring to a periodic table, arrange the atoms Ne, Na, P, Ar, K in order of increasing first ionization energy. 

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Knowledge Required (1) The definition of ionization energy. (2) The periodic trends in first ionization energies within groups and periods. 

The trends in first ionization energies, first electron attachment energies, atomic sizes and electronegativity coefficients of the elements across the groups and down the periods of the periodic classification. 

General trends in first ionization energies of A group elements with position in the periodic table. Exceptions occur at Groups IIIA and VIA. 

Fig- 4 Flowchart concept map showing trend in first ionization energy across Period 3... 

Analyze and Plan We are given the chemical symbols for five elements. To rank them according to increasing first ionization energy, we need to locate each element in the periodic table. We can then use their relative positions and the trends in first ionization energies to predict their order. 

Further exceptions to the general trend in first ionization energies occur at the low ends of Groups 13 and 14, the first ionization energies of T1 and Pb being respectively higher than those of the corresponding elements in period 5, In and Sn. Ilie exceptions are explained by relativistic effects that are dealt with in Section 4.5. 

Within a given group of the periodic table, the first ionization energy decreases with increasing atomic number. This is related to the increase in atomic radius and the decreasing attraction of the nucleus for the increasingly distant outermost electron. It should be mentioned that this trend is not uniformly noted for the transition metals. 

The ionization energy of an atom is defined as the minimum energy necessary to detach an electron from the neutral gaseous atom (see Section 3.3). It can be obtained directly from the photoelectron spectrum of an atomic gas. Appendix F lists measured ionization energies of the elements, and Figure 5.24 shows the periodic trends in first and second ionization energies with increasing atomic number. 

Use the third period of the periodic table as an example to illustrate the change in first ionization energies of the elements as we move from left to right. Explain the trend. 

FIGURE 7.9 shows, for the first 54 elements, the trends we observe in first ionization energy as we move from one element to another in the periodic table. The important trends are as follows ... 

Explaining the trends and discontinuities in first ionization energy across a period... 

Sketch an outline of the periodic table and use it to compare the trends in atomic size, first ionization energy, and electron affinity. 

What general trends are noticeable across the Periodic Table in the values of (a) the first ionization energies, (b) the first electron attachment energies, and (c) the covalent radii of the elements ... 

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