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Electron Configurations

Filling the atoms with electrons

When you complete this presentation, you will be able to ... explain how to write the electron

configuration for an atom using … orbital notation complete electron configuration noble gas electron configuration

Objectives

We have learned how to determine the energy levels of electrons in elements.

We use the periodic table to tell if an electron is in … a particular shell (1, 2, 3, 4, 5, 6,

or 7) and a particular orbital (s, p, d, or f).

Introduction

Now, we are going to learn exactly where the electrons go in an atom.

We have three guides that will help us figure this out. The aufbau principle The Pauli exclusion principle Hund’s rule

Introduction

Electrons occupy orbitals of the lowest energy first.

We learned that the periodic table is a visualization of the energy levels of the orbitals in previous presentations.

Atomic orbitals start with 1s as the lowest energy and go up from there.

The Aufbau Principle

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p

We add electrons into the 1s orbital, then, to the 2s orbital, then, to the 2p orbital, then, to the 3s orbital, and, so on.

We follow the periodic table.

The Aufbau Principle

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p

This says that we can only have a maximum of two electrons in the same suborbital.

One must have a spin of +½ and one a spin of –½.

This means that we can have 2 electrons in each s orbital 6 electrons in each p orbital 10 electrons in each d orbital 14 electrons in each f orbitalPauli Exclusion

Principle

Hund’s rule uses the aufbau principle and the Pauli exclusion principle to show how we add electrons to the suborbitals.

We add a single electron to each suborbital before we double-up the electrons in a suborbital.

Hund’s Rule

For example, in adding electrons to the p-orbital across the 2nd period

Hund’s RuleB: 1s

2s2p

↑↓↑↓

↑


Hund’s RuleC: 1s

2s2p

↑↓↑↓

↑ ↑


Hund’s RuleN: 1s

2s2p

↑↓↑↓

↑ ↑ ↑


Hund’s RuleO: 1s

2s2p

↑↓↑↓

↑↑↓ ↑


Hund’s RuleF: 1s

2s2p

↑↓↑↓

↑↓ ↑↑↓


Hund’s RuleNe: 1s

2s2p

↑↓↑↓

↑↓ ↑↓ ↑↓

The Schrödinger Equation describes the position of the electron in terms of total and potential energy.

The equation gives the position as a likelihood - a probability.

This then leads to the concept of the orbital as an electron cloud.

An electron cloud is the volume of space that contains an electron.

Different kinds of clouds are at different energy levels.

Introduction

There are different kinds of orbitals that make up each energy level.

Each energy level is assigned a principal quantum number.

From 1 to 7 This is the same as the number of periods

in the periodic table. This is no coincidence.

Each energy level is called a “shell.”

Orbitals

The 1st shell contains one orbital: the 1s orbital.

The 2nd shell contains two orbitals: the 2s orbital. the 2p orbital.

The 3rd shell contains three orbitals: the 3s orbital the 3p orbital the 3d orbital

Orbitals

The 4th shell contains four orbitals: the 4s orbital. the 4p orbital. the 4d orbital. the 4f orbital.

And, so on. In actual practice, the 5th shell only contains

four orbitals (the s, p, d, and f orbitals), the 6th shell only contains three orbitals (the s, p, and d orbitals), and the 7th shell only contains two orbitals (the s and p orbitals).

Orbitals

Each orbital has its own: shape number of suborbitals maximum number of electrons energy level

Orbitals

The s orbital has one suborbital and it is shaped like a sphere.

The s orbital is perfectly symmetrical in all axes.

Orbital Shapes

The p orbital has three suborbitals and they are shaped like dumbbells.

Each p orbital is symmetrical to its particular axis.

Orbital Shapes

The d orbital has five suborbitals and they are shaped like 3D clover leaves.

Each d orbital is symmetrical to its particular plane.

Orbital Shapes

The f orbital has seven suborbitals and they are shaped like ... ?

Each d orbital is symmetric in 3-dimensional space.

Orbital Shapes

We only need to remember the shapes of the s and p orbitals.

Orbital Shapes

Each orbital has a specific number of suborbitals available for electrons.

The s-orbital has 1. The p-orbital has 3. The d-orbital has 5. The f-orbital has 7.

Each of the suborbitals can hold a maximum of 2 electrons.

Suborbitals and Electrons

Therefore, each orbital has a maximum number of electrons.

The s-orbital has 2 maximum. The p-orbital has 6 maximum. The d-orbital has 10 maximum. The f-orbital has 14 maximum.


This corresponds to the width of each group on the periodic table.

The s block (Groups 1 and 2) is 2 elements wide.



The p block (Groups 13 - 18) is 6 elements wide.



The d block (Groups 3 - 12) is 10 elements wide.



The f block (lanthanides and actinides) is 14 elements wide.


Each of the orbitals has an energy associated with it.

s-orbitals always have the lowest energy in a shell.

p-orbitals always have the next lowest energy in a shell.

d-orbitals always have the next lowest energy in a shell.

f-orbitals always have the highest energy in a shell.

Orbitals and Energy

We can do a diagram of the estimated energies of the shells and orbitals like this.

Orbitals and Energy1st

shell

2nd shell

3rd shell

4th shell

1s2s2p3s3p3d4s4p4d4f

Lower energy

Higher energy

Actually, it is a little more complicated than this.But this gives you a good idea of the energy distribution in the electron shells of an atom.

In reality, the upper orbitals of 3rd shell and above are higher energy than the lowest orbital of the next higher shell.

Orbitals and Energy1s

2s2p

3s3p3d

4s4p4d4f

Ener

gy

Orbitals and Energy1s

2s2p

3s3p3d 4s

4p4d4f

Ener

gy

5s5p5d5f

6s6p6d

7s7p

From lowest energy to highest energy:

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7pThis looks complicated.

It would be complicated if we had to memorize this.

But, we don’t.

The periodic table is arranged in just this way.

We start with 1s.

Orbitals and Energy


We go to 2s.

Orbitals and Energy


Then to 2p.

Orbitals and Energy


Then to 3s.

Orbitals and Energy


Then to 3p.

Orbitals and Energy


Then to 4s.

Orbitals and Energy


Then to 3d.

Orbitals and Energy


Then to 4p.

Orbitals and Energy


Then to 5s.

Orbitals and Energy


Then to 4d.

Orbitals and Energy


Then to 5p.

Orbitals and Energy


Then to 6s.

Orbitals and Energy


Then to 4f.

Orbitals and Energy


Then to 5d.

Orbitals and Energy


Then to 6p.

Orbitals and Energy


Then to 7s.

Orbitals and Energy


Then to 5f.

Orbitals and Energy


Then to 6d.

Orbitals and Energy


And, finally, to 7s.

Orbitals and Energy


To follow the periodic table, we need to remember a couple of things.

s-orbitals begin in the 1st shell.

Orbitals and Energy

➀


p-orbitals begin in the 2nd shell.

Orbitals and Energy

➀➁


d-orbitals begin in the 3rd shell.

Orbitals and Energy

➀➁

➂


f-orbitals begin in the 4th shell.

Orbitals and Energy

➀➁

➂

➃

If we want to find the orbitals available for an element, we just follow the periodic table.

For example, for oxygen, O

Orbitals and Energy

➀➁

➂

➃


For example, for oxygen, O, we go 1s

Orbitals and Energy

➀➁

➂

➃


For example, for oxygen, O, we go 1s, 2s

Orbitals and Energy

➀➁

➂

➃


For example, for oxygen, O, we go 1s, 2s, 3p.

Orbitals and Energy

➀➁

➂

➃


Oxygen has electrons in the 3p orbital.

Orbitals and Energy

➀➁

➂

➃


For example, for copper Cu

Orbitals and Energy

➀➁

➂

➃


For example, for copper Cu, we go 1s

Orbitals and Energy

➀➁

➂

➃


For example, for copper Cu, we go 1s, 2s

Orbitals and Energy

➀➁

➂

➃


For example, for copper Cu, we go 1s, 2s, 2p

Orbitals and Energy

➀➁

➂

➃


For example, for copper Cu, we go 1s, 2s, 2p, 3s

Orbitals and Energy

➀➁

➂

➃


For example, for copper Cu, we go 1s, 2s, 2p, 3s, 3p

Orbitals and Energy

➀➁

➂

➃


For example, for copper Cu, we go 1s, 2s, 2p, 3s, 3p,4s

Orbitals and Energy

➀➁

➂

➃


For example, for copper Cu, we go 1s, 2s, 2p, 3s, 3p,4s, 3d.

Orbitals and Energy

➀➁

➂

➃


Copper has electrons in the 3d orbital.

Orbitals and Energy

➀➁

➂

➃

We don’t need to use the whole table if we remember where to start our count (s at 1, p at 2, d at 3, and f at 4).

For example, lead, Pb:

Orbitals and Energy

➀➁

➂

➃


For example, lead, Pb: 2p

Orbitals and Energy

➀➁

➂

➃


For example, lead, Pb: 2p, 3p

Orbitals and Energy

➀➁

➂

➃


For example, lead, Pb: 2p, 3p, 4p

Orbitals and Energy

➀➁

➂

➃


For example, lead, Pb: 2p, 3p, 4p, 5p

Orbitals and Energy

➀➁

➂

➃


For example, lead, Pb: 2p, 3p, 4p, 5p, 6p.

Orbitals and Energy

➀➁

➂

➃


Lead has electrons in the 6p orbital.

Orbitals and Energy

➀➁

➂

➃

There are different orbitals that make up each energy level.

Each level is assigned a principal quantum number from 1 to 7

Each level is called a “shell.” Each orbital has its own shape,

number of suborbitals, maximum number of electrons, and energy level.

Summary

We only need to remember the shapes of the s and p orbitals.

Each orbital has a specific number of suborbitals available for electrons, the s-orbital has 1, the p-orbital has 3, the d-orbital has 5, the f-orbital has 7.

Each of the suborbitals can hold a maximum of 2 electrons.Summary

Therefore, each orbital has a maximum number of electrons: the s-orbital has 2 maximum, the p-orbital has 6 maximum, the d-orbital has 10 maximum, and the f-orbital has 14 maximum.

Each of the orbitals has an energy associated with it: s-orbitals always have the lowest energy in a shell, p-orbitals always have the next lowest energy in a shell, d-orbitals always have the next lowest energy in a shell, and f-orbitals always have the highest energy in a shell.

The periodic table is arranged in a way to be able to tell how the energies of orbitals and shells are arranged.Summary

{ electron configurations filling the atoms with electrons

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