Ionization energy across a period

The first ionization energy for boron is lower than what you would predict, based on the general trend for ionization energy across a period. Explain this exception to the trend. 

What exceptions are there in the increase of ionization energies across a period ... 

Recall that metals tend to lose electrons. Thus, the lower the ionization energy, the more reactive the metal. For a group of metals, reachvity increases as the atomic number increases. The opposite is true for nonmetals because nonmetals tend to gain electrons. The higher the ionization energy of a non-metal, the more reactive the nonmetal. For a group of nonmetals, reactivity decreases as the atomic number increases. Of the representative elements, which is the most reactive metal Which is the most reactive nonmetal (Hint What is the trend for ionization energy across a period )... 

Transition metals share properties such as electrical conductivity, luster, and malleability with other metals. There is little variation in atomic size, electronegativity, and ionization energy across a period. However, there are differences in properties among these elements, especially physical properties. For example, silver is the best conductor of electricity. Iron and titanium are used as structural materials because of their relative strength. 

For transition elements, there is little variation in atomic size, electronegativity, and ionization energy across a period. 

Describe and expiain the variation of ionization energy across a period and down a group. 

The variation of ionization energies across a period or within a group is essentially the opposite of that observed for atomic radii. This observation leads us to the following conclusion ... 

FIGURE 14.3 Ionization energy tends to increase from left to right across a period and to decrease down a group. 

Likewise, from left to right across a period, the forces of attraction between the outermost electron and the nucleus increase. Therefore the ionization energies increase while the atomic radii decrease. Refer to Figure 5-2 for the exceptions to the general trends for ionization energy. 

Ionization energy generally increases across a period. Again, this trend is linked to the atomic radius. Across a period, the atomic radius decreases because Zeff increases. The force of attraction between the nucleus and valence electrons is subsequently increased. Therefore, more energy is needed to remove one such electron. 

Periodic trends in ionization energy are linked to trends involving the reactivity of metals. In general, the chemical reactivity of metals increases down a group and decreases across a period. These trends, as well as a further trend from metallic to non-metallic properties across a period, and increasing metallic properties down a group, are shown in Table 3.1. 

FIGURE 14.3 The general tendency of ionization energy is to increase across a period and decrease down a group. This diagram is a highly schematic representation of those trends. 

Periodic trends—Ionization energies increase going from left to right across a period. This is because of the increase in nuclear charge. As the nuclear charge increases, the attraction between the electrons and the nucleus increases. This makes it more difficult to remove an electron from the atom. 

Ionization energy tends to increase across a period. As you go across a period, the attraction between the nucleus and the electrons in the outer energy level increases. Thus, more energy is needed to pull an electron away from its atom. For this trend to be true, you would expect a noble gas to have the highest ionization energy of all the elements in the same period. As you can see in Figure 2.16, they do. 

First ionization energy increases across a period and decreases down a group. 

In Fig. 12.35 we see that there are some discontinuities in ionization energy in going across a period. For example, discontinuities occur in Period 2, in going from beryllium to boron and from nitrogen to oxygen. These exceptions to the normal trend can be explained in terms of how electron repulsions depend on the electron configuration. We will discuss the elements in Period 2 individually to further develop the concept of shielding. 

Ordinarily, the first ionization energy increases as we go across a period, so we might expect sulfur to have a greater ionization energy than phosphorus. However, in this case the fourth p electron in sulfur must be placed in an already occupied orbital. The electron-electron repulsions that result cause this electron to be more easily removed than might be expected. ... 

Ionization energy generally decreases down a group and increases across a period, as shown in this diagram. Darker shading indicates higher ionization energy. 

Ionization Energy Increases as You Move Across a Period... 

Ionization energy, electronegativity, and electron affinity generally increase as you move across a period and decrease as you move down a group. 

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