Question

Using the symbol of the previous noble gas to indicate core electrons, write the valence shell electron configuration for each of the following elements. a. titanium, \(Z=22\) b. selenium, \(Z=34\) c. antimony, \(Z=51\) d. strontium, \(Z=38\)

Short answer

a. Titanium: \([Ar] 4s^2 3d^2\) b. Selenium: \([Ar] 4s^2 3d^{10} 4p^4\) c. Antimony: \([Kr] 5s^2 4d^{10} 5p^3\) d. Strontium: \([Kr] 5s^2\)

Step-by-step solution

a. Titanium (Z=22)

The previous noble gas to titanium (Z=22) is Argon (Z=18). Therefore, we can represent the electron configuration up to argon as [Ar]. Now, we need to determine the electron configuration of the remaining valence electrons. The atomic number of titanium is 22, which means it has 22 electrons. Since Argon has 18 electrons, we have 4 more electrons to distribute in the electron configuration. Following the Aufbau principle, the next orbitals to be filled in the order are 4s and 3d. Distributing the 4 remaining electrons, we get the following configuration: 4s²3d². So, the shorthand electron configuration with noble gas notation for titanium is: \([Ar] 4s^2 3d^2\).

b. Selenium (Z=34)

The previous noble gas to selenium (Z=34) is Argon (Z=18). Therefore, we can represent the electron configuration up to argon as [Ar]. Now, we need to determine the electron configuration of the remaining valence electrons. The atomic number of selenium is 34, which means it has 34 electrons. Since Argon has 18 electrons, we have 16 more electrons to distribute in the electron configuration. Following the Aufbau principle, the next orbitals to be filled in the order are 4s, 3d, and 4p. Distributing the 16 remaining electrons, we get the following configuration: 4s²3d¹⁰4p⁴. So, the shorthand electron configuration with noble gas notation for selenium is: \([Ar] 4s^2 3d^{10} 4p^4\).

c. Antimony (Z=51)

The previous noble gas to antimony (Z=51) is Krypton (Z=36). Therefore, we can represent the electron configuration up to krypton as [Kr]. Now, we need to determine the electron configuration of the remaining valence electrons. The atomic number of antimony is 51, which means it has 51 electrons. Since Krypton has 36 electrons, we have 15 more electrons to distribute in the electron configuration. Following the Aufbau principle, the next orbitals to be filled in the order are 5s, 4d, and 5p. Distributing the 15 remaining electrons, we get the following configuration: 5s²4d¹⁰5p³. So, the shorthand electron configuration with noble gas notation for antimony is: \([Kr] 5s^2 4d^{10} 5p^3\).

d. Strontium (Z=38)

The previous noble gas to strontium (Z=38) is Krypton (Z=36). Therefore, we can represent the electron configuration up to krypton as [Kr]. Now, we need to determine the electron configuration of the remaining valence electrons. The atomic number of strontium is 38, which means it has 38 electrons. Since Krypton has 36 electrons, we have 2 more electrons to distribute in the electron configuration. Following the Aufbau principle, the next orbitals to be filled in the order are 5s. Distributing the 2 remaining electrons, we get the following configuration: 5s². So, the shorthand electron configuration with noble gas notation for strontium is: \([Kr] 5s^2\).

Key concepts

Noble Gas Notation

The concept of noble gas notation simplifies the writing of electron configurations by using the symbol of the previous noble gas. This is particularly useful for elements with long electron configurations. Noble gases are stable and have complete outer shells, which makes them a perfect shorthand reference.

• To use noble gas notation, identify the nearest noble gas prior to the element in the periodic table.
• Write the noble gas symbol in brackets. For example, for titanium, we use [Ar] since Argon is the noble gas that precedes it.

Then, add the electron configuration for the remaining electrons. This compact form helps avoid lengthy electron configuration writing and is especially beneficial for elements with high atomic numbers.

Aufbau Principle

The Aufbau principle dictates the order in which electrons fill orbitals, from the lowest to the highest energy level. It's a German word that means "building up." When writing configurations, it's crucial to follow this rule to correctly fill orbitals.

• Electrons fill orbitals in a sequence, typically starting with 1s, followed by 2s, 2p, 3s, 3p, and so on.
• After the 3p orbitals are filled, we move to 4s, then 3d, because 4s has a lower energy than 3d.

This sequential filling is key when determining where to place remaining electrons after accounting for the core electrons in noble gas notation.

Electron Distribution

Electron distribution helps us understand how electrons are placed in an atom's orbitals. Once the noble gas core has been identified, the remaining electrons fill the higher energy orbitals according to the Aufbau principle.

• The distribution from lower to higher energy levels explains the stability of electron arrangements.
• Each s orbital can hold up to 2 electrons, p orbitals up to 6, d orbitals up to 10, and f orbitals up to 14.

When determining electron distribution, ensure you've allocated electrons to specific orbitals, following their maximum capacity and energy levels.

Periodic Table

The periodic table is a valuable tool when writing electron configurations. It not only helps identify the nearest noble gas for noble gas notation but also shows the sequence of orbitals filled according to energy levels.

• The table arranges elements in groups and periods, reflecting recurring chemical properties.
• Groups are vertical columns and indicate elements with similar chemical behaviors.

Using the periodic table, students can predict electron configurations, understand periodic trends in element properties, and see the organization of elements based on atomic number.

Core Electrons

Core electrons refer to electrons in the inner shells of an atom, excluding the valence electrons which participate in chemical bonding. They are typically represented using noble gas notation.

• Core electrons are found in lower energy levels and do not influence the atom's reactivity as significantly as valence electrons do.
• In noble gas notation, these electrons are condensed into the symbol of the previous noble gas, helping simplify electron configuration notation.

Understanding core electrons is essential for writing electron configurations as it helps distinguish them from valence electrons, aiding in predictions of chemical reactivity and bonding tendencies.