Writing Energy Level Diagrams - 2.5.3 | Unit 2: Atomic Structure | IB Grade 11: Chemistry
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2.5.3 - Writing Energy Level Diagrams

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Introduction to Energy Level Diagrams

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0:00
Teacher
Teacher

Today, we're diving into energy level diagrams, which are crucial for visualizing how electrons are arranged in an atom. Can anyone tell me what we often call the different zones that electrons occupy?

Student 1
Student 1

Are they called energy levels?

Teacher
Teacher

Exactly! Energy levels correspond to the distances of the electrons from the nucleus. We use subshell notations, like 1s or 2p, to indicate these levels. Why do we use different letters like 's' and 'p'?

Student 2
Student 2

Because they have different shapes and energy levels?

Teacher
Teacher

Correct! Each letter indicates a different type of orbital shape. Remember, 's' is spherical, while 'p' shape looks like a dumbbell. These shapes help us understand how electrons crowd around the nucleus.

Constructing an Energy Level Diagram

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0:00
Teacher
Teacher

Let's move on to constructing an energy level diagram. Who can remember what the Aufbau principle states?

Student 3
Student 3

Electrons fill the lowest energy orbitals first before moving to higher ones.

Teacher
Teacher

Exactly! So if we were to draw iron's diagram, how should we start filling it up?

Student 4
Student 4

We should start with the 1s orbital, then 2s, and continue until we get to 3d.

Teacher
Teacher

That's right! And as we fill them, do we have any rules to keep in mind about electron spins?

Student 1
Student 1

Yes! We can't have two electrons with the same spins in an orbital.

Teacher
Teacher

Great! That's the Pauli Exclusion Principle at work.

Example of Iron (Z=26)

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0:00
Teacher
Teacher

Now, let’s apply what we've learned to iron, which as we know has 26 electrons. Can anyone start by telling me the order in which we’ll fill the orbitals?

Student 2
Student 2

We go 1s, then 2s, 2p, 3s, 3p, 4s, and then 3d.

Teacher
Teacher

Exactly! Let's fill those in one by one: 1s², 2s², 2p⁢... Keep going!

Student 3
Student 3

3s², 3p⁢, 4s², and then we fill 3d with 6 electrons.

Teacher
Teacher

Great job! So, summarizing, we can write iron's electron configuration as [Ar] 4s² 3d⁢. Now, let's represent this in our energy level diagram.

Student 4
Student 4

So we write the lines for each subshell and put the arrows in, following Pauli’s and Hund’s principles.

Teacher
Teacher

Exactly, good job! This visual representation will help us understand iron's properties and behavior in bonding.

Introduction & Overview

Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.

Quick Overview

This section explains how to visually represent atomic energy levels and the arrangement of electrons in energy level diagrams.

Standard

In this section, we learn to construct energy level diagrams that depict the arrangement of electrons in various subshells, following established principles like the Aufbau principle and Hund's rule. The section also provides an example with iron (Z=26) to illustrate the practical application of these concepts.

Detailed

Writing Energy Level Diagrams

In this section, we explore the process of constructing energy level diagrams to illustrate how electrons are distributed across different energy levels and subshells in an atom. Energy level diagrams serve as visual representations, allowing us to see the arrangement and energy state of electrons.

Key Concepts in Energy Level Diagrams

  1. Subshell Representation: Each subshell (e.g., 1s, 2s, 2p, etc.) is drawn as a horizontal line on the diagram. The subshells are labeled with their corresponding orbital notations such as 1s, 2s, 2p, 3s, 3p, and so forth.
  2. Electron Placement: Electrons are represented by arrows, with upward arrows (↑) indicating one spin state and downward arrows (↓) indicating the opposite spin state. Electrons are placed in the subshells according to the principles governing electron configurations:
  3. Aufbau Principle: Electrons fill the lowest energy subshells first.
  4. Pauli Exclusion Principle: Each subshell can hold a maximum of two electrons with opposite spins.
  5. Hund’s Rule: For subshells that have multiple orbitals of the same energy (like p, d, f), each orbital gets one electron before any gets a second.

Example: Iron (Z=26)

To illustrate these principles practically, we can construct the energy level diagram for iron, which has an atomic number of 26:
1. The Aufbau sequence for iron up to 26 electrons includes the following subshells filled in order:
- 1sΒ² (2 electrons)
- 2sΒ² (2 electrons)
- 2p⁢ (6 electrons)
- 3sΒ² (2 electrons)
- 3p⁢ (6 electrons)
- 4sΒ² (2 electrons)
- 3d⁢ (6 electrons)
2. The resulting electron configuration for iron can be expressed as [Ar] 4s² 3d⁢.
3. When we construct the energy level diagram, we would place the arrows based on this arrangement, adhering to the principles noted earlier.

Significance

Writing energy level diagrams is essential for understanding how electrons are distributed in an atom, which is crucial in predicting chemical behavior and bonding properties.

Audio Book

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Drawing Energy Levels

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● On paper, you draw each subshell as a horizontal line, label it with its orbital notation (for example, 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, …).

Detailed Explanation

To start creating an energy level diagram, you will represent each subshell (different energy levels where electrons can exist) as a horizontal line. Each line is labeled with its respective orbital notation (like 1s, 2s, 2p, etc.). This visual representation helps you understand how different orbitals stack based on their energy levels. In simpler terms, think of the subshells as barriers on a ladder, where each step represents a different level where electrons can exist. By labeling each line with its notation, you set the stage for understanding how electrons fill these available energy states.

Examples & Analogies

Imagine you’re organizing books on a shelf. Each shelf represents a different energy level (like the lines for the orbitals), and you label each shelf (like 1s, 2s) to denote the type of books stored there. Just as you wouldn’t confuse a shelf for fiction with a shelf for reference materials, this labeling helps keep track of where each type of orbital is located in the energy ladder.

Representing Electrons

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● Then you write small upward (↑) and downward (↓) arrows on each line to represent the electrons, filling from lowest to highest energy, and obeying Pauli’s exclusion (max two arrows per line, one up and one down) and Hund’s rule (in degenerate lines, put one up arrow in each before pairing them).

Detailed Explanation

After drawing the subshells, the next step is to fill them with electrons using arrows. Each electron is represented by an upward arrow (↑) or downward arrow (↓). According to the Pauli Exclusion Principle, a single orbital can hold a maximum of two electrons, which must be represented as one up and one down arrow. For orbitals that have the same energy (like the three 2p orbitals), you initially place one up arrow in each before pairing them with a down arrow. This filling order ensures that the electrons are arranged in the most stable configuration, minimizing interaction and repulsion between them.

Examples & Analogies

Think of a school bus where you want to seat students in a way that avoids unnecessary crowding. Each seat represents an orbital, and students are like electrons. You want to allow one student to sit in each seat (like the up arrows) before pairing them with friends (the down arrows). This way, no one feels cramped, and each student is happier, just like how electrons prefer to occupy separate orbitals to minimize repulsion.

Example with Iron

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● Example: Iron (Z = 26) 1. The Aufbau sequence up to 26 electrons is: 1s β†’ 2s β†’ 2p β†’ 3s β†’ 3p β†’ 4s β†’ 3d β†’ 4p β†’ … 2. Place electrons one by one: β€’ 1sΒ² (2 electrons) β€’ 2sΒ² (2 more; total 4) β€’ 2p⁢ (6 more; total 10) β€’ 3sΒ² (2 more; total 12) β€’ 3p⁢ (6 more; total 18) β€’ 4sΒ² (2 more; total 20) β€’ 3d⁢ (6 more; total 26)

Detailed Explanation

To apply the rules of filling energy levels, you start with elemental Iron, which has 26 electrons. You use the Aufbau principle to follow a sequence that dictates which orbitals fill up first based on increasing energy. You add electrons sequentially to each subshell: both the 1s and 2s can hold a maximum of 2 electrons each, the 2p can hold 6 total, and then you move on to 3s and 3p in a similar manner, filling up to the 4s before you finally fill the 3d orbitals up to 6 for Iron. The final configuration is [Ar] 4s² 3d⁢, ensuring that you have represented all the electrons correctly.

Examples & Analogies

Think of filling up a jar with marbles of different colors. You start by placing the smallest (1s) marbles in first until it is full, then move to the next size (2s) and continue this process until your jar can hold no more. By the end, when every space in the jar is skillfully filled with marbles of increasing size (energy state), you achieve a perfectly organized structure, mirroring how each electron finds its place in an atom.

Definitions & Key Concepts

Learn essential terms and foundational ideas that form the basis of the topic.

Key Concepts

  • Subshell Representation: Each subshell (e.g., 1s, 2s, 2p, etc.) is drawn as a horizontal line on the diagram. The subshells are labeled with their corresponding orbital notations such as 1s, 2s, 2p, 3s, 3p, and so forth.

  • Electron Placement: Electrons are represented by arrows, with upward arrows (↑) indicating one spin state and downward arrows (↓) indicating the opposite spin state. Electrons are placed in the subshells according to the principles governing electron configurations:

  • Aufbau Principle: Electrons fill the lowest energy subshells first.

  • Pauli Exclusion Principle: Each subshell can hold a maximum of two electrons with opposite spins.

  • Hund’s Rule: For subshells that have multiple orbitals of the same energy (like p, d, f), each orbital gets one electron before any gets a second.

  • Example: Iron (Z=26)

  • To illustrate these principles practically, we can construct the energy level diagram for iron, which has an atomic number of 26:

  • The Aufbau sequence for iron up to 26 electrons includes the following subshells filled in order:

  • 1sΒ² (2 electrons)

  • 2sΒ² (2 electrons)

  • 2p⁢ (6 electrons)

  • 3sΒ² (2 electrons)

  • 3p⁢ (6 electrons)

  • 4sΒ² (2 electrons)

  • 3d⁢ (6 electrons)

  • The resulting electron configuration for iron can be expressed as [Ar] 4sΒ² 3d⁢.

  • When we construct the energy level diagram, we would place the arrows based on this arrangement, adhering to the principles noted earlier.

  • Significance

  • Writing energy level diagrams is essential for understanding how electrons are distributed in an atom, which is crucial in predicting chemical behavior and bonding properties.

Examples & Real-Life Applications

See how the concepts apply in real-world scenarios to understand their practical implications.

Examples

  • Constructing an energy level diagram for iron (Z=26) by filling 1sΒ², 2sΒ², 2p⁢, 3sΒ², 3p⁢, 4sΒ², and 3d⁢, to demonstrate the arrangement of electrons.

Memory Aids

Use mnemonics, acronyms, or visual cues to help remember key information more easily.

🎡 Rhymes Time

  • Electrons fill from low to high, each shell and subshell, oh my!

πŸ“– Fascinating Stories

  • Imagine electrons line up for a dance in their orbital shapes. The lower energy orbits are the first ones to fill, resembling a tiered seating arrangement in a theater, where the best views are taken first.

🧠 Other Memory Gems

  • Use All Principles Help for remembering Aufbau, Pauli, and Hund's rules.

🎯 Super Acronyms

Remember the word *IPS* for filling

  • I: - for Increasing energy
  • P: - Pauli Exclusion
  • S: - Hund's Rule.

Flash Cards

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Glossary of Terms

Review the Definitions for terms.

  • Term: Energy Level Diagram

    Definition:

    A visual representation that shows the arrangement of electrons in various subshells within an atom.

  • Term: Aufbau Principle

    Definition:

    A principle stating that electrons occupy the lowest energy orbitals before filling higher energy levels.

  • Term: Pauli Exclusion Principle

    Definition:

    An exclusion principle stating that no two electrons in an atom can have the same set of four quantum numbers.

  • Term: Hund's Rule

    Definition:

    A rule stating that electrons will fill degenerate orbitals singly with parallel spins before pairing.