The Aufbau principle | Atomic structure and properties | AP Chemistry | Khan Academy

Summary

This chemistry lesson focuses on electron configurations, particularly utilizing the Aufbau principle to understand configurations beyond calcium. The instructor explains how to determine electron configurations for elements like neon, argon, and calcium, highlighting the order in which subshells are filled. The video also clarifies misconceptions about the order of filling subshells, especially for elements like scandium. Additionally, it introduces the concept of blocks in the periodic table, categorizing elements into S, P, and D blocks based on the subshells they are filling.

Takeaways

• 🌟 Orbitals and subshells are fundamental to understanding electron configurations in atoms.
• 🔍 The Aufbau principle, derived from the German word for 'building,' is crucial for electron configurations beyond calcium.
• 💡 Neon's electron configuration is 1s²2s²2p⁶, illustrating the filling order of subshells.
• 📚 The periodic table reflects the order of subshell filling, with elements in each period corresponding to a specific shell.
• 🎓 Argon's electron configuration uses noble gas notation, building on neon's configuration with additional electrons in the 3s and 3p subshells.
• 🔧 Calcium's electron configuration (4s²) deviates from filling the 3d subshell first, demonstrating a key exception to the Aufbau principle.
• 🌌 Scandium's electron configuration (4s²3d¹) shows the start of the 3d subshell filling after the 4s subshell, according to the Aufbau principle.
• 🧠 The Aufbau principle is a useful tool for visualizing electron configurations, but it may not always reflect the actual order of electron addition in reality.
• 📊 The periodic table is divided into blocks (S, P, D) based on the subshells being filled, which helps categorize elements and predict their properties.
• 🔬 The D block in the periodic table, including elements like scandium, is named for the perceived filling of d subshells, even though the actual electron filling may differ.

Q & A

What is the origin of the term 'Aufbau principle'?

The term 'Aufbau principle' comes from German and translates to 'building principle' in English.

What is the electron configuration of neon?

The electron configuration of neon is 1s2 2s2 2p6, which corresponds to its atomic number of 10.

How does the Aufbau principle assist in determining electron configurations past calcium?

The Aufbau principle is a method used to predict the order in which atomic subshells are filled with electrons, which is particularly useful for electron configurations beyond calcium.

What is the significance of the order in which subshells are filled as per the periodic table?

The order in which subshells are filled, such as 1s, 2s, 2p, 3s, 3p, etc., corresponds to the order in which elements are arranged in the periodic table.

What is the electron configuration of argon, and how does it relate to neon?

Argon's electron configuration is the same as neon's, which is 1s2 2s2 2p6, but with the addition of two electrons in the 3s subshell and six electrons in the 3p subshell, making it 3s2 3p6.

Why does calcium have its electrons in the 4s subshell instead of the 3d subshell when following the Aufbau principle?

According to the Aufbau principle, calcium's electron configuration is the same as argon's, but with two additional electrons in the 4s subshell instead of the 3d subshell, resulting in the configuration ending in 4s2.

How does the electron configuration of scandium differ from that of calcium?

Scandium, having one more proton than calcium, has an electron configuration that includes two electrons in the 4s subshell (4s2) and one electron in the 3d subshell (3d1), following the Aufbau principle.

What is the significance of the S, P, and D blocks in the periodic table?

The S, P, and D blocks in the periodic table correspond to the subshells that are being filled as you move across the table. The S block includes elements filling their s subshells, the P block includes elements filling their p subshells, and the D block includes elements that appear to be filling their d subshells based on electron configurations, although the actual filling order can be more complex.

Why is the D block named as such, and what does it represent?

The D block is named so because it was historically thought that the elements in this block were filling their d subshells as you move across the periodic table. However, the actual electron configurations may not always follow this pattern, especially beyond calcium.

How does the Aufbau principle simplify the understanding of electron configurations in chemistry?

The Aufbau principle simplifies the understanding of electron configurations by providing a systematic way to predict the order in which subshells are filled, which is crucial for determining the electron configuration of elements in the periodic table.