chapter 4: glow in the dark. glow in the dark this chapter will introduce the chemistry needed to...

Chapter 4: Glow in the Dark

Glow in the dark

This chapter will introduce the chemistry needed to understand how glowing things workSection 4.1: History of the atomSection 4.2: Atomic Structure/Bohr ModelSection 4.3: Electron StructureSection 4.4: Periodic tableSection 4.5: PeriodicitySection 4.6: Light & Matter

Section 4.2 Atomic Structure

The atom is defined as the smallest particle of an element that retains the properties of that element.

It consists of 2 regions & 3 sub-atomic particles

What’s in an atom?

An atom is made of three sub-atomic particles

Particle Location

Nucleus

Nucleus

Outside the nucleus

Mass

1 amu = 1.6710-27 kg

1 amu = 1.6710-27 kg

0.00055 amu

9.1010-31 kg

Charge: Fix

+1

0

-1

Proton

Neutron

Electron

1 amu (“atomic mass unit”) = 1.66 10-27 kg

The TWO Regions of the Atom

Electron Cloud: contains electrons and mostly empty space

: dense center containing the protons & neutrons

Counting Subatomic Particles: Mass Number

The total number of protons + neutrons in the nucleus is called the mass number.

To calculate mass number: 2 options

1. Round atomic mass from periodic table

to a whole number Nitrogen’s atomic mass = 14.01 amu

mass # = 14

2. Add the # protons and # neutrons of an

atom together

Mass # = protons + neutrons

Counting Subatomic Particles: Atomic Number

Every atom has a different number of protons which determines the identity of the atom

The atomic number shows the number of protons. Atomic number = protons

To get the Atomic Number: Find the whole number of the element from the periodic table

Nitrogen’s Atomic # = 7

Counting Subatomic Particles: Number of Neutrons

To calculate the number of neutrons: 2 options

1. Subtract the atomic number from the mass number

2. Subtract the proton# from the mass #

# Neutrons = Mass # - Atomic #

14 -7 = 7 neutrons

Neutral Atoms vs Charged Atoms (IONS)

A neutral atom has the same number of protons and electrons

A ion has a different number of protons and electrons leaving it with a charge.

How to calculate number of electrons:Subtract electron number from proton

number.

Overall Charge = protons - electrons

-1 = 35 - electrons

Atomic number for Br = 35 = # of protons

Charge = -1

Electrons = 36

Determining the Number of Electrons

Charge = # of protons – # of electrons

Atomic number = # of protons

Example:How many electrons does Br-1

have?

+3 = 13 - electrons

Atomic number for Al = 13 = # of protons

Charge = +3

Electrons = 10

Determining the Number of Electrons

Charge = # of protons – # of electrons

Atomic number = # of protons

Example:How many

electrons does Al+3 have?

XA C

Z

Displaying Information of atoms: Nuclear Symbol

Charge# protons - # electrons(assumed to be “0” if blank)

Element Symbol1 or 2 letters, found on

the periodic table

Mass number# protons + # neutrons

Atomic number # of protons

Example: Nuclear symbol

O16 -2

8

Charge-2

Element SymbolO = Oxygen

Mass number16

Atomic number 8

8 p

10 e

8 n

Self Check

What are the number of protons, neutrons & electrons in each atom?

19F-1 57Fe 204Hg 9 26 80

9 p10 e10 n

26 p26 e31 n

80 p 80 e124 n

Displaying Information of atoms: Hyphen notation

NuclearSymbol

Hyphen Notation

Atomic #

Mass #

Charge Proton Neutron Electron

Magnesium-25 +2

82 126 82

copper – 65 mass number

Element Name

Find the Missing Values

Let’s Practice

Nuclear Symbol

Hyphen Notation

Atomic #

Mass #

Charge Proton Neutron Electron

Magnesium -25 +2

82 126 82

Remember: Atomic number is the identityAtomic number = protonsCharge = proton - electronsMass # = protons + neutrons

12 25 12 13 10

Lead-208 208 0 82

22512

Mg

Pb20882

How do Atoms Differ?

Isotopes– are atoms of the same element with a different number of neutrons or mass number

Some isotopes are radioactive—but not all…many are quite stable!

Most elements contain a mixture of 2 or more isotopes. Each one having its own

mass and abundance.

Identifying Isotopes

12C 13C

Carbon-12 Carbon-13

Isotopes can be differentiated by their different mass numbers in the element symbol

Or by the mass number following their name.

Isotopes

Mass Number versus Atomic Mass

Mass Number Average Atomic Mass

# of protons + # of neutrons Average of actual masses

For one specific isotope only

Is not found on the periodic table

Weighted average of all isotopes

Is found on the periodic table

Always a whole number Not a whole number

Calculating aWeighted Average!

Practice Problems:(1) Mrs. Soto’s chemistry semester grades are calculated using a

weighted average of three category scores: Major Grades= 60% of your gradeMinor Grades= 30% of your gradeSemester Exam=10% of your grade

• If a student had the following scores, what would they receive for the semester?

Major= 80 Minor= 60

Semester Exam=65

Weighted AverageStep (1): Multiply each score by the % that it is weighted.Step (2): Add these products up, and that is the weighted average!

60% x 80 = 48.030% x 60 = 18.0

10% x 65 = 6.5 Add them up!!

A “normal average” would be calculated by simply adding the raw scores together and dividing by 3…

80 + 60 + 65 = 205 ÷ 3 = 68.3 = D

+

72.5

Calculating Average Atomic Mass

Average atomic mass

= Abundance of isotope

Mass of isotope

( )

Average atomic mass is a weighted average of the masses of all naturally occuring isotopes.

“Sum of”

What fraction of the time is that isotope present?

Actual mass (not mass number)

Example of Finding Average Atomic Mass

966.362422.0969.347578.0 amuMassAvg

Example:Find the atomic mass of

chlorine Chlorine-35 has a mass of 34.969 amu.Chlorine-37

has a mass of 36.966 amu & is 24.22% abundant.

Remember that percents add up to 100.

So they said the second isotope is present 24.22% of the time.

This means that the first isotope is present 100 -24.22 = 75.78% of the time

Isotope Mass Percent Decimal

1 34.969 amu 75.78 0.7578

2 36.966 amu 24.22 0.2422

This chart summarizes the information in the problem:

= 35.45 amu (this is what’s on the periodic table for Cl!)

SELF CHECK! Example:Element X has 2 natural isotopes. Calculate the average atomic mass. 1st isotope has a mass of 10.012 a.m.u with 19.91% abundance. 80.09% of the 2nd element has a mass of 11.009 a.m.u.


1 10.012 amu 19.91 .1991

2 11.009 amu 80.09 .8009


= 10.81 amu (Element X is Boron!)

SELF CHECK !

Example:Calculate the average atomic mass of copper if it has 2 isotopes. 69.11% has a mass of 62.93 a.m.u and the rest has a mass of 64.93 a.m.u.

Remember that percents add up to 100.

So they said the first isotope is present 69.11% of the time.

This means that the second isotope is present 100-69.11 = 30.89% of the time


1 62.93 amu 69.11 .6911

2 64.93 amu 30.89 .3089


= 63.55 amu

Lets focus in on the electrons in the electron cloud!

Niehls Bohr performed experiments with hydrogen & light.

Electron are in ENERGY LEVELS according to how much energy they have. Only certain energy amounts are allowed.

Think of the energy levels as rungs of a ladder. The farther away an energy level is from the nucleus, the more Energy it attains!

Electrons can move from one energy level to the next by gaining or losing energy (quanta).Ground State: An electron is as close to the nucleus as it can get.

Excited State: An electron in a higher energy level than it should be.

Bohr believed electrons were located in Energy Levels (SHELLS)

“excited state”

“groundstate”

Bohr Models: show how the electrons are situated within the energy levels

http://www.youtube.com/watch?v=Cn6v5ygyZHQ A maximum of 2 electrons are placed in the first shell. A maximum of 8 electrons are placed in the second shell. A maximum of 18 electrons are placed in the third shell. Only 8 electrons can be placed in the 3rd shell at first, then 2 electrons will move into the 4th shell and remaining electrons will be placed back in the 3rd shell until the max of 18.

**(Just know this : it will be explained in the next section)** A maximum of 32 electrons are placed in the 4th shell.

***Valence Electrons are the outermost electrons found in the highest, outermost energy level of the atom***

http://www.youtube.com/watch?v=Cn6v5ygyZHQ

Bohr Atomic Models

Lewis Dot DiagramsA way to show the valence electrons in an atom. The symbol represents the nucleus and inner core

electrons. The dots represent the valence electrons.

Only 2 dots per side. Only 4 sides. Maximum of 8 valence electrons.

Add dots one at a time on each side until each side is full. Then add a second dot to make a pair when needed. Exception is Helium. It can look like this:

He: or He

1920: Bohr Models are not accurate! Let me introduce you to the Quantum Mechanical Model

Bohr Models are still used to simplify the atom. HOWEVER

Modern atomic theory uses calculus equations to show how the subatomic electrons act as both particles and waves

These equations show the most probable location of electrons in the atom (known as atomic orbitals)

Quantum Mechanical Model

In theory, we really don’t know the exact location of an electron. We can only estimate the likelihood of it being in a certain region ofspace called an orbital

Protons, Neutrons & Electrons Wksht

Symbol Atomic# Protons Neutrons Electrons Mass #

B 5 5 6 5 11

Na 11 11 13 11 24

Ga 31 31 37 31 68

Y 39 39 50 39 89

Cu 29 29 35 29 64

Tc 43 43 57 43 100

Pb 82 82 125 82 207

Protons, Neutrons & Electrons Wksht

Symbol Atomic# Protons Neutrons Electrons Mass #

Yb 70 70 102 70 172

Ac 89 89 136 89 225

Mo 42 42 53 42 95

Tl 81 81 125 81 206

Fm 100 100 159 100 259

No 102 102 159 102 261

Yb 70 70 102 70 172

Sg 106 106 159 106 265

Atom Wksht : Isotopes

Hyphen Notation Nuclear Symbol

Atomic #

Mass #

protons electrons Neutrons

Carbon-13 C 6 13 6 6 7

Sodium-23 11 23 11 11 12

Iodine-126 53 126 53 53 73

Neon-20 10 20 10 10 10

Phosphorus-31 15 31 15 15 16

Magnesium-25 12 25 12 12 13

Atom Wksht : Isotopes

Hyphen Notation Nuclear Symbol

Atomic #

Mass # protons electrons Neutrons

Lead-206 Pb 82 206 82 82 124

Mercury-202 Hg 80 202 80 80 122

Strontium-90 Sr 38 90 38 38 52

Hydrogen-1 H 1 1 1 1 0

Hydrogen-2 H 1 2 1 1 1

Uranium-238 U 92 238 92 92 146

Uranium 235 U 92 235 92 92 143

Ion Wksht: Part III

Ion Symbol Atomic Number

Mass # protons electrons neutrons Nuclear charge

F-1 9 19 9 10 10

Al-+3 13 27 13 10 14

Ca+2 20 40 20 18 20

S-2 16 32 16 18 16

P-3 15 31 15 18 16

K+1 19 39 19 18 20

Br-1 35 80 35 36 45

Se-2 34 79 34 36 45

Fe+3 26 56 26 23 30

Atomic Dimensions: Element Sym

bolAtomic #

Mass # P+ N e- Isotope, ION, or Neutral atom

Aluminum Al 13 27 13 14 13 n. atom

Bromine Br 35 80 35 45 36 ion

Uranium U 92 238 92 146 92 N atom

Helium He 2 4 2 2 2 isotope

Helium He 2 5 2 3 2 isotope

Lithium Li 3 7 3 4 2 ion

Tungsten W 74 184 74 110 74 N atom

Xenon Xe 54 133 54 79 54 Neutral Atom

Magnesium Mg+2 12 24 12 12 10 Positive ion

Atomic Dimensions: Element Symb

olAtomic #

Mass # P+ N e- Isotope, ION, or Neutral atom

Carbon C 6 12 6 6 6 Neutral atom

Carbon C 6 14 6 8 6 isotope

Nitrogen N 7 14 7 7 7 N atom

Section 4.2—Electron Structure “The Electron Hotel”

Restaurant

The story of the Electron Hotel

A man built an hotel for electrons with a restaurant next door.

But he was making so much money that he decided to add on with some more rooms and a parking garage.

He still had high demand and decided to add on some more rooms and a shopping center.

He used the last space he could to put some rooms above the shopping center.

Parking GarageShopping Center

Restaurant

How the Electron Hotel Fills

This man had some very strange ideas about how to run his hotel. He insisted four things:

• The lowest possible must be used first (actually it was the fire inspector that insisted on this one)

• There can only be one person in a room until all rooms at that level have someone

• No more than 2 people to a room• When two people are in a room, they must be of opposite sex

If 8 people come to the hotel, where would he put them?

Parking GarageShopping Center

http://classroomclipart.com/cgi-bin/kids/imageFolio.cgi?action=view&link=Clipart/Symbols&image=cricon5.jpg&img=12&tt=








RestaurantParking Garage

Another Example






Shopping Center






















RestaurantParking Garage

Shopping Center

SELF CHECK!
















































Where do electrons really live?

Electron Clouds

They don’t live in a hotel…They are in the area outside of the nucleus where the electrons reside.

Electron Clouds

Electron cloud

Principal energy levels

(shells)

Sublevels(subshells)

Orbitals

The electron cloud is made of energy levels.

Energy levels are composed of sublevels.

Sublevels have orbitals.

Electron Hotel

Which floor of the hotel

Which area of the hotel?

Which room?

Energy Levels

There are 7 energy levels. The period number on the periodic table

correlates to the energy level

Ca has electrons up to energy level 4

Cl has electrons up to energy level 3

Sublevels(subshells): a set of orbitals with equal energy

“S” subshell

Spherical shapedOnly 1 orbital (orientation/position) in 3-D spaceFirst seen in the 1st energy levelCan hold a maximum of 2 electronsRepresented on the periodic table as groups 1A and 2A + helium

“P” Subshell

Dumbbell shapedThere are 3 orbitals(positions in 3-D space)First seen in the 2nd energy levelCan hold a maximum of 6 electronsRepresented on the periodic table as groups 3A -6A

“D” Subshell

Four lobed shapedThere are 5 orbitals First seen in the 3rd energy levelCan hold a maximum of 10 electronsRepresented on the periodic table as the transition metals (group B)

“F” Subshell

Too complex to name shapeThere are 7 orbitalsFirst seen in the 4th energy levelCan hold a maximum of 14 electronsRepresented on the periodic table as the inner transition metals (lower block)

The Most Probable Location for an Electron!

Orbital– Area of high probability of the electron being located.

Each orbital can hold 2 electrons

To calculate the total number of orbitals in an energy level, use 2(n)2

Summary

Electron Configuration

Is an address of an electronElectrons must be placed in the lowest energy levels first (ground state)

4p1

Energy Level

# of electrons

subshell

Energy and Subshells

1s

2s

3s

4s

5s

2p

3p

4p

5p

3d

4d

6s

6p5d

4f

Ene

rgy

Subshells are filled from the lowest energy level to increasing energy levels.

Does this look familiar? Electron Hotel!

3 rules that govern electron configurations

Aufbau Principle:Electrons must fill the lowest available subshells and orbitals before moving on to the next higher energy subshell/orbital.

1

Filling order is: 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p

Can use the periodic table as a guide to fill from lowest to highest sublevels or memorize filling order

An orbital can overlap within different energy levels, such as 4s is lower in energy than 3d

How Electron Configurations Relate to the Organization of the Periodic Table

sp

d

f

Figure 11.31: Orbitals being filled for elements in various parts of the periodic table.

Hund’s Rule

Hund’s Rule: Place electrons in unoccupied orbitals of the same energy level before doubling up.

2

How does this work?

If you need to add 3 electrons to a p subshell, add 1 to each before beginning to double up.

Pauli Exclusion Principle

Pauli Exclusion Principle: Two electrons that occupy the same orbital must have opposite spins.

3

“Spin” is designated with an up or down arrow.

How does this work?

If you need to add 4 electrons to a p subshell, you’ll need to double up. When you double up, make them opposite spins.

Electron Configurations

Determine the number of electrons to place1

Fill in subshells until they reach their max (s = 2, p = 6, d = 10, f = 14) or use periodic table as a guide.3

Follow Aufbau Principle for filling order2

The total of all the superscripts is equal to the number of electrons.4

0 = 16 - electrons

No charge written Charge is 0

Atomic number for S = 16 = # of protons

Electrons = 161s 2s 2p 3s 3p2 2 6 2 4

2 2 6 2 4+ + + + = 16

Example:Write

electron configuration

for S


0 = 19 - electrons


Atomic number for K = 19 = # of protons

Electrons = 19

1s 2s 2p 3s 3p62 2 6 2 4s1

2 2 6 2 6 + 1+ + + + = 19

Example:Write electron configuration for K


0 = 22 - electrons


Atomic number for Ti = 22 = # of protons

Electrons = 22

1s 2s 2p 3s 3p62 2 6 2 4s2

2 2 6 2 6 + 2 + 2+ + + + =22

Example:Write electron configuration for Ti

3d2

What is Orbital Notation?

It shows the grouping and position of electrons in an atom.

The number and configuration of electrons determines how something glows…so it’s important to know “where the electrons live” for an atom!

Orbital Notation use boxes or lines for orbitals and arrows for electrons.

Drawing Orbital Notation (boxes & arrows)

Aufbau Principle: Electrons fill subshells (and orbitals) so that the total energy of atom is the minimum1

Pauli Exclusion Principle: Two electrons that occupy the same orbital must have different spins.3

Hund’s Rule: Place electrons in unoccupied orbitals of the same energy level before doubling up.2

Example:Write the

orbital notation for

Cl

Drawing Orbital Notations

Aufbau Principle: Electrons fill subshells (and orbitals) so that the total energy of atom is the minimum1

0 = 17 - electrons


Atomic number for Cl = 17 = # of protons

Electrons = 17

Pauli Exclusion Principle: Two electrons that occupy the same orbital must have different spins.3

Hund’s Rule: Place electrons in unoccupied orbitals of the same energy level before doubling up.2

1s 2s 2p 3s 3p

4231567910111213141516178

Example:Write the


Cl


0 = 7 - electrons


Atomic number for N = 7 = # of protons

Electrons = 7

1s 2s 2p

42315679101112131457

Example:Write the

orbital notation for N


0 = 26 - electrons


Atomic number for Fe = 26 = # of protons

Electrons = 26

1s 2s 2p 3s 3p4231567910111213141526

Example:Write the


Fe

4s 3d

Shorthand Notation (Noble Gas Notation)

Noble Gas– Group 8 of the Periodic Table. They contain full valence shells.

Noble Gas Notation– Noble gas is used to represent the core (inner) electrons and only the valence shell is shown.

1s 2s 2p 3s 3p2 2 6 2 6 4s 2 3d 10 4p 5

4s 2 3d 10 4p 5[Ar]

BrComplete electron configuration

Noble gas

The “[Ar]” represents the core electrons and only the valence electrons are shown

How do you know which noble gas to use to symbolize the core electrons?

Which Noble Gas Do You Choose?

Think: Price is Right.

How do you win on the Price is Right?

By getting as close as possible without going over.

Choose the noble gas that’s closest without going over!

Noble Gas # of electrons

He

Ne

Ar

Kr

Xe

2

10

18

36

54

Noble Gas Notation Example


Start where the noble gas left off and write electron configuration for the valence electrons3

Determine which noble gas to use2

Example:Write noble gas notation

for Fe



Start where the noble gas left off and write spectroscopic notation for the valence electrons3

Determine which noble gas to use2

0 = 26- electrons


Atomic number for Fe= 26= # of protons

Electrons = 26

[Ar] 4s 3d2 6

18 2 6+ + = 26Closest noble gas: Ar (18)

Ar is full up through 3p


for Fe


0 = 56 - electrons


Atomic number forBa= 56 = # of protons

Electrons = 56

[Xe] 6s 2

54 2+ = 56

Closest noble gas:Xe (54)

Xeis full up through 4p


forBa

Exceptional confuguration

Half-filled or completely filled d & f sublevels have ________ energies and are more stable than partially filled d’s and f’s.

This means that an atom can “borrow” one of its “s” electrons from the previous orbital to become more stable.

___ __ __ __ __ __

5s 4d

becomes

___ __ __ __ __ __

5s 4d

Because the 4d sublevel is now full, the atom is at a lower energy state and therefore more stable.

↓↑ ↓↑ ↓↑ ↓↑ ↓↑ ↑

↑ ↓↑ ↓↑ ↓↑ ↓ ↑ ↑↓

Electron Configuration for Ions

Determine the number of electrons to place. Positive ions lose electrons; negative ions gain electrons.

1

Fill in subshells until they reach their max (s = 2, p = 6, d = 10, f = 14) or use periodic table as a guide.3

Follow Aufbau Principle for filling order2

The total of all the superscripts is equal to the number of electrons.4

-2 = 16 - electrons

Atomic number for S = 16 = # of protons

Electrons = 181s 2s 2p 3s 3p2 2 6 2 6

2 2 6 2 6+ + + + = 18

Example:Write

electron configuration

for S-2

chapter 4: glow in the dark. glow in the dark this chapter will introduce the chemistry needed to...

Documents