Electron Arrangement

Electron Arrangement

Unit 3

NC Essential StandardsChm.1.1.2 • Analyze diagrams related to the Bohr model of the hydrogen atom in terms of allowed, discrete energy levels in the emission spectrum. • Describe the electron cloud of the atom in terms of a probability model. • Relate the electron configurations of atoms to the Bohr and electron cloud models.  Chm.1.1.3 • Understand that energy exists in discrete units called quantaDescribe the concept of ground and excited states of electrons in an atom1. When an electron gains an amount of energy equivalent to the energy difference, it moves from its ground state to a higher energy level. 2. When the electron moves to a lower energy level, it releases an amount of energy equal to the energy difference in these levels as electromagnetic radiation (emissions spectrum). • Articulate that this electromagnetic radiation is given off as photons. • Understand the inverse relationship between wavelength and frequency, and the direct relationship between energy and frequency. • Use the “Bohr Model for Hydrogen Atom” and “Electromagnetic Spectrum” diagrams from the Reference Tables to relate color, frequency, and wavelength of the light emitted to the energy of the photon. • Explain that Niels Bohr produced a model of the hydrogen atom based on experimental observations. This model indicated that: 1. an electron circles the nucleus only in fixed energy ranges called orbits; 2. an electron can neither gain or lose energy inside this orbit, but could move up or down to another orbit; 3. that the lowest energy orbit is closest to the nucleus. • Describe the wave/particle duality of electrons.

Energy is related to the Electron’s orbits

• When an atom is:

• The electron will:– Start at the – Jump to – Number of jumps is related to

• Key researchers: Bohr, Plank, Einstein

Schrodinger

Overview

Bohr’s Model of the Atom

• Electrons orbit the nucleus at:

• Electrons can be excited by:

• When excited, an electron will absorb only a certain amount of energy, (

Bohr’s model

• When excited, the electron

– Called the _________ state• The electron does not stay in the excited

state but falls back toward the nucleus and releases

Bohr’s model

Bohr’s model

• Ground vs. excited state

• Number of electrons that exist at specific energy levels

• Bohr’s model works for hydrogen but not for the complex atoms

Development of the Modern Atomic Model

Here are several models of the atom as they were developed in history:

............ ......

................

Electron Cloud Model

• Quantum Mechanical Model– Based on determining the probable location

of the electron

– Within the boundary of the

atom, its electrons can be

found 90% of the time

(based on probability)

Methods for Writing Electron Arrangements

• Orbital notation

• Electron configuration

• Noble gas notation

How are you going to remember the names for each method of writing the electron arrangement?

Rules for Electron Arrangement

• Aufbau:• Place the electron at the lowest energy orbital

possible. * • Pauli’s exclusion principle: Place a maximum of

2 electrons in each orbital.

• Hund’s rule: Place an electron in each orbital of a sublevel before pairing up.

* Check the diagram for the order of increasing energy level

Electron Arrangement Diagram

• n= principal energy level • Sublevels – s, p, d, f• Orbitals

– Each orbital holds 2 electrons with opposite spins, shown by arrows:

Incr

easi

ng E

nerg

y

Nucleus

Energy Diagram

n = principal energy level

Sublevels:

Orbitals

Electrons & spin

SPUD FarmMemory tool

Principal Energy Level Location of theValence electrons

Incr

easi

ng E

nerg

y

Nucleus

Energy Diagram

n = principal energy level

Sublevels:

Orbitals

Electrons & spin

Examples: Sulfur & Iron

Incr

easi

ng E

nerg

y

Nucleus

Energy Diagram

n = principal energy level

Sublevels:

Orbitals

Electrons & spin

Students:

Phosphorus

Calcium

Krypton

Incr

easi

ng E

nerg

y

Nucleus

Energy Diagram

n = principal energy level

Sublevels:

Orbitals

Electrons & spin

Incr

easi

ng E

nerg

y

Nucleus

Energy Diagram

n = principal energy level

Sublevels:

Orbitals

Electrons & spin

Orbital Notation

• The orbital is indicated by a line____ wioth the name written below.

• Arrows represent the electrons.• Examples

Ne: ___ ___ ___ ___ ___

1s 2s 2p 2p 2p

___ ___ ___ ___ ___ ___ ___ ___ ___ ___

Note: You must write both the lines and the orbital designations under the lines

1s

1s

1s 2s

1s 2s

1s 2s 2p

1s 2s 2p

1s 2s 2p

1s 2s 2p

1s 2s 2p

1s 2s 2p

1s 2s 2p 3s

Element Atomic # Orbital diagram Electron Configuration

H

He

Li

Be

B

C

N

O

F

Ne

Na

Practice• Element Atomic #

(Z)• H

• He

• Li

• Be

• B

• Orbital Notation___1s___ 1s ___ ___ 1s 2s___ ___1s 2s___ ___ ___ ___ ___1s 2s 2p 2p 2p

Practice

• C

• N

• O

• F

• Ne

___ ___ ___ ___ ___

1s 2s 2p 2p 2p

___ ___ ___ ___ ___

1s 2s 2p 2p 2p

___ ___ ___ ___ ___

1s 2s 2p 2p 2p

___ ___ ___ ___ ___

1s 2s 2p 2p 2p

___ ___ ___ ___ ___

1s 2s 2p 2p 2p

Electron Configuration

• Principal energy level + sublevel • Use superscripts to show number of

electrons in each sublevel

1s² 2s² 2p⁶ 3s² 3p⁶ 4s²

Electron Configuration: Sublevel diagram

• Determining order: Aufbau rules

n=1

n=2

n=3

n=4

n=5

• see figure 5-19 on p.138

Know how to make this chart!

1s

1s

1s 2s

1s 2s

1s 2s 2p

1s 2s 2p

1s 2s 2p

1s 2s 2p

1s 2s 2p

1s 2s 2p

1s 2s 2p 3s

Element Atomic # Orbital diagram Electron Configuration

H

He

Li

Be

B

C

N

O

F

Ne

Na

Check your electron configuration answers using the Periodic Table

Periods

S, P, D, F Blocks

18

Valence Electrons

• Electrons in the outermost (highest) principal energy level– Important– Participate in bonds to make compounds– 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²

1s² 2s² 2p⁶ 3s² 3p⁴ 1s² 2s² 2p⁶ 3s¹1s² 2s²1s¹

Review: Electron Configuration

Write • Potassium

• Aluminum

• Chlorine

Circle the valence electrons.

Electron Dot Notation

• Represents valence electrons

K Al Cl

Maximum number = 8

Octet rule: atoms will lose, gain or share electrons to have 8 valence electrons & become stable

Introducing Noble Gas Notation

Analyze the following examples and propose the rules for writing Noble Gas Notation.

• chlorine [Ne] 3s²3p⁵• iron [Ar] 4s²3d⁶• zinc [Ar] 4s²3d¹⁰• barium [Xe] 6s²

Noble Gas Notation

• Short cut method for electron arrangement• Use the noble gas in the period above the

element

• Example:Na 1s² 2s² 2p⁶ 3s¹- Use Neon - Represent neon’s configuration 1s² 2s² 2p⁶as [Ne]- Use in Na: [Ne] 3s¹

Noble Gas Notation

Element

1s² 2s² 2p⁶ 3s² 3p⁶

1s² 2s² 2p⁶ 3s² 3p⁴ 1s² 2s² 2p⁶ 3s¹

1s² 2s² 2p⁶

Noble Gas Notation

Element1s² 2s² 2p⁶ 3s² 3p⁶ 4s²

3d¹º4p⁶ 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹º4p⁵ 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²

3d¹º4p⁴ 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹º

4p¹1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹

1s² 2s² 2p⁶ 3s² 3p⁶

Noble Gas Notation

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹º 4p⁶ 5s²4d¹⁰ 5p⁵

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹º4p⁶ 5s² 4d¹⁰5p⁴

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹º4p⁶ 5s² 4d¹⁰5p²1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹º4p⁶ 5²1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹º4p⁶

Periodic Table: Order based on Electron

Configuration

Identify element– Write atomic number (Z)– Symbol

• Circle or highlight the valence electrons• Write the electron dot notation

1 18

2 13 14 15 16 17

3 4 5 6 7 8 9 10 11 12

Write the Electron Dot in the correct location for the element

Electron Configuration

• Aufbau is the Rule.Note: However, sometimes the electron

configurations are written in energy level sequence rather than Aufbau sequence.

• This is mostly used for the “d” sublevel.Aufbau sequenceTi: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d²Energy level sequenceTi: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d² 4s²