Question

Using the periodic table as a guide, write the condensed electron configuration and determine the number of unpaired electrons for the ground state of (a) \(\mathrm{Si},\) (b) \(\mathrm{Zn}\), (c) \(\mathrm{Zr},(\mathrm{d}) \mathrm{Sn}\) (e) \(\mathrm{Ba},(\mathrm{f}) \mathrm{Tl}\)

Short answer

(a) Si: electron configuration \(1s^2 2s^2 2p^6 3s^2 3p^2\), 2 unpaired electrons; (b) Zn: electron configuration \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10}\), 0 unpaired electrons; (c) Zr: electron configuration \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^2\), 2 unpaired electrons; (d) Sn: electron configuration \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^{10} 5p^2\), 2 unpaired electrons; (e) Ba: electron configuration \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^{10} 5p^6 6s^2\), 2 unpaired electrons; (f) Tl: electron configuration \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^{10} 5p^6 6s^2 4f^{14} 5d^{10} 6p^1\), 1 unpaired electron.

Step-by-step solution

(a) Silicon (Si) Electron Configuration and Unpaired Electrons

Silicon's atomic number is 14. The electron configuration follows the order: 1s, 2s, 2p, 3s, 3p. Therefore, Silicon's electron configuration is: 1s² 2s² 2p⁶ 3s² 3p². To determine the unpaired electrons, we look at the highest energy level subshell (3p). There are two unpaired electrons in the 3p subshell.

(b) Zinc (Zn) Electron Configuration and Unpaired Electrons

Zinc's atomic number is 30. The electron configuration follows the order: 1s, 2s, 2p, 3s, 3p, 4s, 3d. Therefore, Zinc's electron configuration is: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰. Zinc has no unpaired electrons (all subshells are filled).

(c) Zirconium (Zr) Electron Configuration and Unpaired Electrons

Zirconium's atomic number is 40. The electron configuration follows the order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d. Therefore, Zirconium's electron configuration is: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d². To determine the unpaired electrons, we look at the highest energy level subshell (4d). There are two unpaired electrons in the 4d subshell.

(d) Tin (Sn) Electron Configuration and Unpaired Electrons

Tin's atomic number is 50. The electron configuration follows the order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p. Therefore, Tin's electron configuration is: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p². To determine the unpaired electrons, we look at the highest energy level subshell (5p). There are two unpaired electrons in the 5p subshell.

(e) Barium (Ba) Electron Configuration and Unpaired Electrons

Barium's atomic number is 56. The electron configuration follows the order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s. Therefore, Barium's electron configuration is: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s². To determine the unpaired electrons, we look at the highest energy level subshell (6s). There are two unpaired electrons in the 6s subshell.

(f) Thallium (Tl) Electron Configuration and Unpaired Electrons

Thallium's atomic number is 81. The electron configuration follows the order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p. Therefore, Thallium's electron configuration is: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p¹. To determine the unpaired electrons, we look at the highest energy level subshell (6p). There is one unpaired electron in the 6p subshell.

Key concepts

Periodic Table

The periodic table is a powerful tool for understanding the properties and behaviors of elements. It arranges all known elements in an order that highlights periodic trends, which are patterns in the properties of elements. Each element is placed according to its atomic number, which increases from left to right across a period. Also, elements are sorted into groups or columns that share similar chemical properties.

• The periodic table helps predict the electronic configuration of an element, as elements in the same group often have similar outer shell electron arrangements.
• For example, using the periodic table, you can easily find that Silicon (Si) is in Group 14, and like other elements in its group, it has four electrons in its outermost shell.

Thus, the periodic table not only provides valuable information about individual elements but also about overall chemical trends.

Unpaired Electrons

In the study of electron configuration, identifying unpaired electrons is crucial because they largely determine the magnetic properties and chemical reactivity of an element. Unpaired electrons are the electrons that exist alone in an orbital and are not paired with another electron with an opposite spin.

• To determine the number of unpaired electrons, look at the highest energy orbitals in an element's configuration. If there are orbitals that are only partially filled, there may be unpaired electrons present.
• For instance, in the element Silicon (Si), with the electron configuration \(1s^2 2s^2 2p^6 3s^2 3p^2\), the 3p subshell contains two electrons in different orbitals, thus resulting in two unpaired electrons.

The presence of unpaired electrons can make an element paramagnetic, meaning they are attracted to magnetic fields.

Atomic Number

The atomic number of an element is perhaps its most foundational property. It is simply the number of protons found in the nucleus of an atom of the element. This number also determines the element's identity and its placement on the periodic table.

• The atomic number is denoted by \(Z\) and it tells us how many electrons are in a neutral atom, as it must balance the number of protons.
• For example, Silicon has an atomic number of 14, which means it has 14 protons and, in a neutral state, 14 electrons.

The atomic number increases as we move across a period or down a group, leading to an increase in the atomic mass and the complexity of electron arrangements.