Hund's Rule

Summary

This script explains electron configuration using electron-box diagrams, starting with 1s orbital holding two electrons spinning in opposite directions. It follows the Aufbau principle, filling lower orbitals first, then discusses filling 2p orbitals using Hund's Rule, which states that degenerate orbitals are half-filled before being completely filled. The script emphasizes understanding electron configurations for different elements by following the periodic table or Aufbau diagram.

Takeaways

• 📚 Electron configuration involves filling electron orbitals according to specific rules.
• 🔵 Each s sublevel can hold two electrons with opposite spins (1s²).
• 📈 Following the Aufbau principle, fill lower energy orbitals before moving to higher ones.
• 🔵 The 2s sublevel also holds two electrons, one spinning up and one down.
• 🌀 In the 2p sublevel, there are five electrons to be distributed among three orbitals.
• 📝 Hund's Rule states that degenerate orbitals are half-filled before being completely filled.
• 🔵 Degenerate orbitals have the same energy, which applies to all three 2p orbitals.
• 📌 Half-fill the 2p orbitals first with electrons spinning up, then fill the rest spinning down.
• ⚠️ 1s and 2s orbitals are not degenerate; they have different energies due to different principal quantum numbers.
• 🔑 Understanding the periodic table and Aufbau diagram is crucial for determining electron configurations.
• 📝 Mastering electron configurations is essential for answering questions about various elements.

Q & A

What are electron-box diagrams?

Electron-box diagrams are visual representations where electrons within each orbital are physically shown.

How many electrons can an s orbital hold?

An s orbital can hold two electrons, which must spin in opposite directions.

What is the significance of the Aufbau principle in electron configuration?

The Aufbau principle requires filling the lower energy orbitals before moving on to the higher energy orbitals.

How many electrons are in the 2s orbital?

The 2s orbital also holds two electrons, one spinning up and the other spinning down.

How many electrons are typically in the 2p orbitals?

There are five electrons in the 2p orbitals, which are distributed among three p orbitals.

What is Hund's Rule and how does it apply to filling the 2p orbitals?

Hund's Rule states that degenerate orbitals should be half-filled before they are completely filled. This means that each of the three 2p orbitals gets one electron before any orbital gets a second electron.

What does the term 'degenerate' mean in the context of orbitals?

In the context of orbitals, 'degenerate' means that they have the same amount of energy.

Why are the 2p orbitals considered degenerate?

The 2p orbitals are considered degenerate because they are all 2 orbitals and all p orbitals, hence they have the same energy.

How does the energy of 1s and 2s orbitals differ?

The 1s and 2s orbitals have different energies because they have different principal quantum numbers (1 and 2 respectively).

What is the importance of knowing the periodic table version for electron configuration?

Knowing the periodic table version helps in understanding the order in which orbitals are filled, which is crucial for determining the electron configuration of elements.

Can you provide an example of how to fill the 2p orbitals following Hund's Rule?

Following Hund's Rule, you would first place one electron in each of the three 2p orbitals with their spins up. Then you would place the remaining two electrons in the orbitals with their spins down.

Outlines

00:00

🔬 Introduction to Electron-Box Diagrams

This section introduces electron-box diagrams, a method of visually representing electrons in orbitals. The speaker explains that the small boxes represent electron orbitals in different sublevels. The focus is on how to fill these orbitals with electrons, starting with the 1s orbital, which can hold two electrons with opposite spins (one up, one down). This method is essential for understanding the configuration of electrons in atoms.

🧲 Aufbau Principle: Filling Lower Orbitals First

Here, the Aufbau principle is discussed, which dictates that lower orbitals must be filled before moving on to higher ones. The example of 2s is used to show that this orbital can also hold two electrons with opposite spins. This principle is fundamental to understanding the order in which orbitals are filled as electrons are added to an atom.

⚛️ Hund's Rule and Degenerate Orbitals

The focus shifts to Hund's Rule, which states that electrons must first half-fill degenerate orbitals (orbitals with the same energy) before completely filling them. The 2p orbitals are used as an example, where the three degenerate orbitals are first filled with one electron each (all pointing up) before electrons are paired with spins in the opposite direction. This method minimizes electron repulsion in atoms.

💡 Difference Between Degenerate and Non-Degenerate Orbitals

This paragraph clarifies the difference between degenerate and non-degenerate orbitals. While degenerate orbitals (like the 2p orbitals) have the same energy, orbitals with different numbers (like 1s and 2s) do not. The numbers correspond to different energy levels, which is why 1s and 2s have different energies, despite both being s orbitals. This distinction is key to correctly filling electron orbitals in an atom.

📚 Mastering Electron Configurations

The final part encourages mastering various types of electron configurations, whether by using the periodic table or the Aufbau diagram. Understanding these configurations allows one to determine the arrangement of electrons in different elements. The speaker emphasizes the importance of familiarizing oneself with the periodic table to answer questions related to electron configuration efficiently.

Keywords

💡Electron Configuration

Electron configuration refers to the distribution of electrons in an atom's orbitals. It's a fundamental concept in chemistry that helps determine an element's properties and behavior. In the video, electron configuration is the main theme, as it explains how electrons are arranged in orbitals and sublevels, starting with the 1s orbital and moving up to the 2p orbitals.

💡Electron Orbitals

Electron orbitals are regions in an atom where electrons are most likely to be found. They are represented as 'little boxes' in the script, each corresponding to a sublevel. The video script describes how these orbitals are filled according to the Aufbau principle and Hund's Rule, emphasizing their importance in understanding electron configurations.

💡Sublevels

Sublevels are categories within an electron shell that include different types of orbitals (s, p, d, f). The script mentions filling the 1s and 2s sublevels before moving on to the 2p sublevel, illustrating the step-by-step process of electron configuration.

💡Aufbau Principle

The Aufbau Principle states that electrons fill orbitals in order of increasing energy. The script uses this principle to explain the order in which the orbitals are filled, starting with the lowest energy orbitals (1s) and moving to higher energy ones (2s, 2p).

💡Hund's Rule

Hund's Rule specifies that electrons will fill degenerate orbitals singly and with parallel spins before pairing up. The script applies Hund's Rule to the 2p sublevel, explaining that the three 2p orbitals are filled with one electron each (half-filled) before any are paired.

💡Degenerate Orbitals

Degenerate orbitals are orbitals that have the same energy level. The script explains that all three 2p orbitals are degenerate and must be half-filled before any are completely filled, according to Hund's Rule.

💡Spin

Spin is an intrinsic property of electrons, which can be thought of as them spinning on their axes. The script mentions that electrons in the same orbital must have opposite spins (one spins up, the other down), which is a key aspect of electron configuration.

💡Electron-box Diagrams

Electron-box diagrams are visual representations of electron configurations, showing how electrons are arranged in orbitals. The script introduces these diagrams as a tool to physically show the electrons within each orbital, aiding in understanding the configuration process.

💡1s2

The notation '1s2' refers to the electron configuration of the 1s orbital being filled with two electrons. The script uses this notation to illustrate the filling of the 1s orbital, which is the first step in the electron configuration process.

💡2p5

The notation '2p5' indicates that the 2p sublevel has five electrons. The script uses this to show how electrons are distributed among the three degenerate 2p orbitals, following Hund's Rule.

💡Periodic Table

The Periodic Table is a tabular arrangement of elements based on their atomic number, electron configuration, and recurring chemical properties. The script suggests using the periodic table as a reference to understand electron configurations and to answer related questions.

Highlights

Electron-box diagrams physically show the electrons within each orbital.

1s sublevel holds two electrons that must spin in opposite directions.

According to the Aufbau principle, lower orbitals must be filled before higher orbitals.

2s sublevel also holds two electrons, spinning one up and one down.

In 2p, all three orbitals have the same energy level (degenerate).

Hund's Rule states that degenerate orbitals are half-filled before fully filled.

Degenerate orbitals have the same energy because they are in the same sublevel (2p).

In filling degenerate orbitals, you must first place one electron (spin up) in each before adding the second (spin down).

1s and 2s orbitals are not degenerate because they have different energy levels.

Electron orbitals are filled following specific rules, including the Aufbau principle and Hund's Rule.

Hund's Rule ensures that electron orbitals of the same energy level are filled evenly to minimize repulsion.

The periodic table can be used to determine electron configurations.

Electron configuration begins with understanding how sublevels and orbitals are filled.

The periodic table version or the Aufbau diagram can be used to calculate electron configurations.

Electron configuration follows an organized process, starting with lower-energy orbitals.

Transcripts

Now, we've done the electron configuration.

Now, you see these little boxes here, these represent the electron orbitals for each one

of those sublevels that we have here.

We're going to fill them in.

We call these electron-box diagrams, where we physically show the electrons within each

one of these orbitals.

We're going to say we start out with one s.

How many does s hold?

It holds two.

Remember, I told you, they have to spin in opposite directions.

One spins up, the other one spins down.

That's 1s2.

We can then move on to 2s following Aufbau principle because we have to fill in the lower

orbital first before we move onto the next one.

This one also has two.

One up, one down.

Now, in 2p we have five electrons.

But here's the thing, all three of these electron orbitals, all three of them are p, 2p orbitals,

so they all have the same exact energy.

We're going to have to follow Hund's Rule to correctly fill it out.

Hund's Rule states that electron orbitals that are degenerate, so remember that word,

degenerate, are first half filled before they are totally filled.

Degenerate just means that they have the same amount of energy.

We know that these three electron orbitals have the same energy because they're all two

orbitals and they're all p orbitals, so they're all 2p orbitals.

We're going to half fill them first.

We'd say up, up, up.

You half fill them first.

You do this because they all have the same energy.

Then you loop back around.

Down, down.

That's how you would fill out the 2p.

Just remember that.

When you're dealing with degenerate orbitals, they have the same number, they have the same

letter, therefore they have the same energy.

You half fill them first before you totally fill them in.

Come back around and start filling them pointing down.

1S and 2s are not degenerate.

They may have the same letter, but they definitely don't have the same number.

1 is 1 and 2 is 2.

Because they have different numbers, they have different energies.

That's the beginning of electron configuration, guys.

There are different types of electron configurations that we're still going to need to know and

master, but this is the beginnings of it.

Remember, as long as you can follow either the periodic table version or the Aufbau diagram

version, then you should be able to do the electron configuration of many different types

of elements.

Just remember, what does this periodic table version look like and use it to answer those

types of questions.