Electrons and Spectra

🧪 Electron Cloud Structure

Electron Behavior in Atoms

Electrons move very fast, spin, are repelled by each other, and are attracted to the positively-charged nucleus. The electron cloud is very large compared with the tiny nucleus, practically weightless, and takes up significant space despite electrons being very small.

Energy Levels and Shells

Electron clouds contain shells (also called energy levels or n numbers) arranged in rings:

⚛ Subshells and Orbitals

Four Subshell Types

The periodic table is organized into 4 distinct sections based on electron cloud shapes:

• s subshell: holds 2 electrons (1 orbital)

• p subshell: holds 6 electrons (3 orbitals)

• d subshell: holds 10 electrons (5 orbitals)

• f subshell: holds 14 electrons (7 orbitals)

Orbital Structure

Each orbital holds 2 electrons spinning in opposite directions. Subshells are composed of orbitals, with the number of orbitals determining maximum electron capacity.

📝 Writing Electron Configurations

Configuration Rules

1. Start with lowest energy first (1s)

2. Follow the 4 sections of the periodic table

3. Electrons in each section should add up to total

4. Recognize overlap between s and d blocks

5. Stop on the target element

Configuration Format

The notation follows: subshell where:

• = energy level/row

• subshell = s, p, d, or f

• = number of electrons
  
  for subshell d, n = n - 1, and for f n = n - 2

Practice Examples

Fluorine (F):

• Atomic number 9 = 9 electrons

• 2 electrons in 1st shell, 7 in 2nd shell

Boron (B):

Argon (Ar):

Copper (Cu):

Tellurium (Te):

🎯 Key Patterns

Periodic Table Organization

• s-block: Groups 1-2

• p-block: Groups 13-18

• d-block: Transition metals

• f-block: Lanthanides and actinides

Energy Level Overlap

As energy levels increase, sublevels branch and create points of overlap, particularly between s and d orbitals, affecting electron filling order in transition metals.

🎯 Learning Objectives

Today's outcome: Analyze the locations of electrons and relate to the Periodic Table and valence electrons.

Standard: HS-PS1-1 - Use the Periodic Table as a model to predict the relative properties of elements based on the patterns of electrons in the energy levels of an atom.

⚛ Atomic Structure Overview

The nucleus (highlighted in pink) contains protons and neutrons, while electrons occupy specific regions called electron clouds around the nucleus.

🔬 Electron Behavior in the Electron Cloud

Electrons in the electron cloud exhibit several key behaviors:

• Move at very high speeds

• Spin while moving

• Experience repulsion from other electrons

• Are attracted to the positively-charged nucleus

🏗 Electron Cloud Organization

Carbon Atom Example

• 6 protons (blue)

• 6 neutrons (red)

• 6 electrons (green)

Electron Shells

• Inner shell: 2 electrons

• Outer shell: 4 electrons

Subshell Types

• s subshell

• p subshell

• d subshell

• f subshell

🎆 Real-World Connection: Fireworks and Electrons

The colors in fireworks result from electrons in different elements absorbing energy and jumping to higher energy levels, then releasing that energy as light when they return to lower levels.

🌟 The Electron Cloud Model

The electron cloud represents the probability distribution of electrons around the nucleus. This model shows that electrons don't orbit in fixed paths but exist in regions of space called orbitals.

Key components of atomic structure:

• Electron shells - main energy levels (represented by numbers 1, 2, 3...)

• Subshells - subdivisions within shells (s, p, d, f)

• Orbitals - specific regions where electrons are likely found

📊 Periodic Table Blocks

The periodic table is organized into four distinct blocks based on electron configurations:

This diagram illustrates how the periodic table's structure directly relates to electron configurations, with each block representing different subshell types.

🔄 Writing Electron Configurations

The standard method for writing electron configurations follows these principles:

1. Start with 1s (lowest energy)

2. Move through subshells in order of increasing energy

3. Follow the diagonal rule (follow arrows on configuration diagrams)

4. Account for overlap between s and d orbitals

This visual guide shows the correct order for filling electron orbitals, following the red arrows from 1s → 2s → 2p → 3s and so on.

📝 Example Configurations

Fluorine (Atomic number 9):

Iron (Fe):

The diagram breaks down iron's configuration, showing how electrons distribute across different energy levels and subshells.

⚡ Shortcut Method Using Noble Gases

For longer configurations, use noble gas notation:

Standard: Arsenic (As) -

Shortcut:

🧮 Orbital Capacities

Each subshell type has specific orbital and electron capacities:

📈 Orbital Diagrams

Orbital diagrams use arrows to represent electrons in individual orbitals:

• Lines represent individual orbitals

• Up/down arrows show electron spin (opposite spins pair up)

• Sodium example:

This diagram clearly shows how electrons fill orbitals, with paired electrons having opposite spins (arrows pointing in opposite directions).

🎯 Key Principles

• Pauli Exclusion Principle: Each orbital holds maximum 2 electrons with opposite spins

• Hund's Rule: Electrons fill degenerate orbitals singly before pairing

• Aufbau Principle: Electrons occupy lowest energy orbitals first## 📝 Orbital Diagrams and Electron Configuration

Key Rule for Orbital Diagrams

When writing orbital diagrams, we follow all the same rules for configurations but we add one: When there is more than one orbital in a sublevel, make sure each orbital has one electron before doubling up.

Nitrogen Example

The orbital diagram for nitrogen shows:

• 1s²: 2 electrons (paired)

• 2s²: 2 electrons (paired)

• 2p³: 3 electrons (unpaired in separate orbitals)

⚡ Energy Shell Diagrams

Energy shell diagrams show the total number of electrons in a given energy level (n) regardless of the sublevel.

Vanadium (V) Example:

• Atomic number: 23

• Electron configuration:

• 2 electrons in the 1st energy level

• Energy "shell" corresponds to n value

🔬 Valence Electrons

Valence electrons are the outermost electrons (those in the highest energy shell). These are the electrons involved in chemical bonding.

🎯 Lewis Dot Structures

Lewis dot structures visually represent:

• Valence electrons as dots around the element symbol

• Covalent bonds as shared electron pairs

• Lone pairs as non-bonding electron pairs

📊 Noble Gas Configurations and Electron Dot Structures

The table below shows period 3 elements with their noble gas configurations and electron dot structures:

Key observations:

• Sodium (Na) has 1 valence electron (highlighted in red)

• Elements are organized by group numbers 1-18

• Each element shows:

  • Noble gas configuration

  • Number of valence electrons

  • Electron dot structure

Valence Electrons 🧪

Valence electrons are electrons in the outermost energy level of an atom. These electrons determine an element's chemical properties and reactivity.

Alkali Metals Configuration

The electron configurations for the first 3 alkali metals show a clear pattern:

Halogens Configuration

The halogens demonstrate the same pattern with 7 valence electrons:

Lewis Dot Diagrams ⚛

Lewis dot diagrams are a notation using chemical symbols and dots to represent valence electrons, named after scientist Lewis who first used this notation.

Key Principles:

• Electrons are negative and repel one another, so space them apart

• Electrons tend to be in pairs as they spin in opposite directions

Drawing Lewis Dot Diagrams for Oxygen

Step-by-step process:

1. Determine electron configuration: (6 valence electrons)

2. Use element symbol: O

3. Pretend there's a "box" around the symbol

4. Place electron "dots" one at a time around the box

5. Account for all valence electrons with no more than 2 on any given side

The final diagram shows all 6 valence electrons properly distributed around the oxygen symbol.

Atomic Energy States ⚡

Key Vocabulary:

Electromagnetic Radiation 📡

The electromagnetic spectrum encompasses all types of electromagnetic radiation, from gamma rays to radio waves.

Key Relationship:

The difference between gamma rays (deadly to humans) and radio waves (which pass through us 24/7 as we use them for TV, Radio, Cell phones, etc.) is the wavelength, which relates to energy.

Bohr Model Applications 🌟

Energy Absorption and Release:

1. Energy is absorbed by an electron

2. As energy is absorbed, the electron is pushed into an "excited" state

3. Atoms are not stable in excited states and will return to ground state

4. When returning to ground state, energy is released (Law of Conservation)

Wave Equations and Electron Transitions 🌊

Fundamental Wave Equation:

or

Where:

• = speed of light = m/s

• (lambda) = wavelength (measured in m)

• (nu) = frequency (Hz or s⁻¹)

Electron Transition Series: