Problem 41 - Chemistry: The Central Science

Question

(a) What is the general relationship between the size of an atom and its first ionization energy? (b) Which element in the periodic table has the largest ionization energy? Which has the smallest?

Step-by-Step Solution

Answer

(a) The general relationship between atomic size and ionization energy is that as atomic size increases, ionization energy decreases, and as atomic size decreases, ionization energy increases. This is due to the varying attraction force between the nucleus and electrons. (b) Helium (He) has the largest ionization energy, while Francium (Fr) has the smallest ionization energy in the periodic table.

Step 1: Define ionization energy and atomic size

Ionization energy is the amount of energy required to remove an electron from a gaseous atom or ion. The general trend for ionization energy is that it increases from left to right across a period and decreases down a group in the periodic table. Atomic size is the distance between the nucleus of an atom and its outermost electrons. The general trend for atomic size is that it increases down a group and decreases from left to right across a period in the periodic table.

Step 2: Relationship between atomic size and ionization energy

The general relationship between atomic size and ionization energy is that as atomic size increases, ionization energy decreases, and as atomic size decreases, ionization energy increases. This is because, as the atom becomes larger, electrons are further from the nucleus and experience a weaker attraction force from the nucleus. As a result, it's easier to remove an electron, and the ionization energy decreases. Conversely, as the atom becomes smaller, electrons are closer to the nucleus and experience a stronger attraction force from the nucleus, making it more difficult to remove an electron. Hence, the ionization energy increases.

Step 3: Identify the element with the largest ionization energy.

To identify the element with the largest ionization energy, we should look for an element with the smallest atomic size, since the ionization energy and atomic size are inversely related. In the periodic table, ionization energy generally increases from left to right across a period and decreases down a group. Therefore, the element with the largest ionization energy should be located at the top-right corner of the periodic table. In this case, the element is Helium (He), which has the largest ionization energy.

Step 4: Identify the element with the smallest ionization energy.

To identify the element with the smallest ionization energy, we should look for an element with the largest atomic size, since the ionization energy and atomic size are inversely related. In the periodic table, atomic size increases down a group and decreases from left to right across a period. Therefore, the element with the smallest ionization energy should be located at the bottom-left corner of the periodic table. In this case, the element is Francium (Fr), which has the smallest ionization energy.