7. Think and discuss: As you move down a group, you will recall that the radius increases. Why do you think an increase in atomic radius would result in a lower

ionization energy?

8. Think and discuss: As you move across a period, you will recall that the radius decreases.

Why do you think a decrease in atomic radius would result in a greater ionization energy?

9. Predict: Electron affinity (EA) refers to the energy released when an electron is added to

an atom. This release of energy is always expressed as a negative value. The greater the

magnitude of the negative value, the greater the attraction for electrons. (An EA of -100

kJ/mol would indicate a stronger attraction for electrons than an EA of -50 kJ/mol.)

How do you think the size of an atom will affect its ability to attract additional electrons?

See explanation

Explanation:

7. As we move down the group more shells are added. The addition of more shells means that the atom becomes larger and the outermost electron is now at greater distance from the nucleus and screening effect becomes very important. This greater screening effect of the inner electron reduces the magnitude of effective nuclear charge on the outermost electron thereby lowering the ionization energy.

8. As we move across the period, the effective nuclear charge increases without a corresponding increase in the number of shells. As a result of this, the outermost electron becomes more tightly bound to the nucleus as the atom becomes smaller and atomic radius decreases causing a rise in the ionization energy from left to right across a period.

9. Actually, the smaller an atom is the greater its electron affinity. The smaller the atom is, the more the outermost shell is drawn closer to the nucleus and this means that the atom is better able to attract electrons to itself.

It is due to the size of atom which varies its force of attraction.

As you move down a group, the atomic radius increases due to addition of more number of shells in an atom.  This increase in atomic radius would result in a lower  ionization energy because the valance electron is farther from the nucleus and held with weak attractive force so less energy is required to remove it.

While on the other hand, as we move from left to right in a periodic table the atomic radius decreases due to addition of more electrons which shrinks the atom and brought the valance shell closer to the nucleus so it becomes harder to remove an electron because the nucleus held these electrons very tightly.

The size of an atom will affect its ability to attract additional electrons because of its force of attraction. Atoms with small radius has more ability to attract electrons due to higher force of attraction as compared to higher atomic radius atoms.

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