Question

In each of the following sets of elements, which element would be expected to have the highest ionization energy? a. \(\mathrm{Cs}, \mathrm{K}, \mathrm{Li}\) b. \(\mathrm{Ba}, \mathrm{Sr}, \mathrm{Ca}\) c. I , Br , Cl d. \(\mathrm{Mg}, \mathrm{Si}, \mathrm{S}\)

Short answer

The elements with the highest ionization energy for each set are: a. \(Li\) b. \(Ca\) c. \(Cl\) d. \(S\)

Step-by-step solution

Set a: Cs, K, Li

We can find these elements in the periodic table. Cs is in period 6, group 1, K is in period 4, group 1, and Li is in period 2, group 1. Recall that ionization energy increases across a period and decreases down a group. In this case, since all elements are in the same group, we can compare their ionization energies based on their periods. Li is the highest up, and therefore, it has the highest ionization energy.

Set b: Ba, Sr, Ca

Ba is in period 6, group 2, Sr is in period 5, group 2, and Ca is in period 4, group 2. Since they are all in the same group, we can compare their ionization energies based on their periods. Ca is the highest up, and therefore, it has the highest ionization energy.

Set c: I, Br, Cl

I is in period 5, group 17, Br is in period 4, group 17, and Cl is in period 3, group 17. Since they are all in the same group, we can compare their ionization energies based on their periods. Cl is the highest up, and therefore, it has the highest ionization energy.

Set d: Mg, Si, S

Mg is in period 3, group 2, Si is in period 3, group 14, and S is in period 3, group 16. In this case, all elements are in the same period, so we will compare their ionization energies based on their groups. As we move across a period from left to right, ionization energy increases. S is furthest right, and therefore, it has the highest ionization energy. In conclusion, the elements with the highest ionization energy for each set are: a. Li b. Ca c. Cl d. S

Key concepts

Periodic Table

The periodic table is an organized chart of all known elements, based on increasing atomic number. Each element has a unique placement according to its atomic structure, specifically the number of protons in its nucleus. This systematic arrangement reveals patterns that can help predict the behavior of elements.

Understanding ionization energy, which is the energy required to remove an electron from an atom, is made easier by the periodic table. In general, ionization energy increases as you move from left to right across a period (row). This happens because electrons are added to the same energy level, but the increasing number of protons in the nucleus pulls more strongly on these electrons.

Additionally, ionization energy decreases as you move down a group (column). Here, electrons are added to higher energy levels further away from the nucleus. The increased distance and additional electron shielding reduce the attraction between the nucleus and the outermost electrons.

Atomic Structure

To truly grasp the nature of ionization energy, we must delve into atomic structure. Each atom consists of three primary subatomic particles: protons, neutrons, and electrons.

• Protons: Positively charged particles found in the nucleus. The number of protons determines the atomic number and the identity of the element.
• Neutrons: Neutrally charged particles also located in the nucleus. They contribute to the atomic mass but have no effect on the charge of the atom.
• Electrons: Negatively charged particles that orbit the nucleus in certain regions called energy levels or shells.

In ionization, we focus mainly on electrons. The outermost electrons (valence electrons) are the easiest to remove and thus are the primary players when considering ionization energy. Forces between electrons and the nucleus are influenced by the number of protons. More protons usually result in a stronger pull on the electrons, increasing the ionization energy.

Electron Configuration

Electron configuration refers to the arrangement of electrons in an atom's electron shells or energy levels. This configuration helps explain many of the properties of elements, including their ionization energy.

The ground state electron configuration fills electrons into the lowest available energy levels first. For example, the configuration of Lithium ( Li) is 1s² 2s¹, indicating its electrons fill up the first shell completely and start the second shell with one electron.

As we move across a period in the periodic table, electrons fill into higher subshells. For instance, as we arrange elements in a period from left to right, we fill electrons into the same primary energy level but different subshells. This increases the effective nuclear charge, attracting electrons more strongly and thus requiring more energy to remove an electron.

A detailed understanding of these principles helps predict which elements will exhibit higher or lower ionization energies based on their unique electron arrangements.