Electrons in Atoms

Where are they?

Energy Levels

Orbits around the nucleus can also be called shells or energy levels.

Diagram: (Fig. 13.3)

• The energy levels in an atom are sort of like _________ of a ladder.

• The more energy an electron has, the __________ away from the nucleus it usually will be.

• The energy levels are not evenly spaced. They get ___________ together as you travel farther away.

• To move from one “rung” to another requires a “____________” of energy.

Energy Levels

rungs

farther

closer

quantum

continuous energy levels quantized energy levels

Figure 11.15: The difference between continuous and quantized energy levels.

Quantum Numbers

• Describe the ______________ of the e-’s around the nucleus.

• Quantum #’s are sort of like a home _____________ for the electron.

• This information about the location of the e-’s in an atom can be used to:

(1) determine chemical & physical _____________ for the elements.

(2) show how the _______________ __________ is organized.

(3) show _____ and _____ elements combine to form compounds.

location

address

properties

Periodic Table

how why

The Four Quantum Numbers

1. Principal Q. #: Describes the _____________ that the electron is from the nucleus. The bigger the number, the ___________ away the electron is.

Example: (1=closest, 2, 3, 4...farther away) These distances are sometimes called _____________________________ ____________.

12

3 nucleus

distance

farther

principal energy levels

2. Orbital Q. #: Describes the __________ of the electron’s path around the nucleus with a letter: (s, p, d, & f) These are sometimes called “_____________”.

s=_____________ cloud; p=_____________ or a 3-D figure 8;

shape

sublevels

spherical ellipsoid

• d & f orbital shapes are complex ________- _______________ ellipsoids, and some d’s and f’s are an ellipsoid with a doughnut or two around the middle.

• All of these orbital shapes are based on the probability of finding the electron in the cloud.

d - orbitals

f - orbitals

crisscrossing

Figure 11.22: How principal energy levels can be divided into sublevels.

s

s

s

s

p

p

p

f

d

d

A Way to Visualize s, p, d, and f sublevels

1 sublevel

2 sublevels

3 sublevels

• Magnetic Q. #: tells how many _________________ in 3-D there are about the nucleus for each orbital shape.

s=___ orientation p= ___ orientations... (x, y, and z)

d= ___ orientations f= ___ orientations

• The orientations are represented with a line or a box.

• _________ electrons can fit into _______ orientation.

Examples: ___ This means a __________ orbital at a distance of 1s “__” (close) to the nucleus. This orbital is

centered about the x, y, and z axis.

□ □ □ This represents an ___________ orbital with its 4p ____ possible orientations at a distance of ___” from the nucleus.

orientations

1 3

5 7

spherical

ellipsoid3 4

1

oneTwo

Figure 11.23: Principal energy level 2 shown divided into the 2s and 2p sublevels

• Spin Q. #: describes how the electron in an orientation is spinning around the nucleus. This spin can be thought of as “____” or “________”. (Some like to imagine it spinning “clockwise” and “counterclockwise”.) The spin is represented as an ___________ in the direction of the spin.

Example: ↑ This represents one electron in a _________ 2s orbital with spin “____” at a distance of “___” from the nucleus.

• Remember, the four quantum numbers tell us the location, or “address” of each electron in an atom.

• This information is vital in understanding the layout of the Periodic Table and the reasoning behind why and how atoms form bonds.

updown

arrow

sphericalup 2

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.

• Finding the last electron in the electron configuration:

• What element has the last electron as 2p4?

• Where is the last electron for Iron?

Electron Configurations

Row on Period Table (except

d’s and f’s)

How many electrons are in the block

(reading left to right)Block of the

Periodic Table

4s2

Oxygen

3d5

• Electron configurations are notations that represent the four Quantum #’s for all of the electrons in a particular atom. Here are the rules for these notations:

• Rule #1 (Aufbau Principle): Electrons fill ________ energy orbitals first.

Examples: 1s would be filled before ____

3s would fill before ____

Electron Configurations

lowest

2s

3p

Electron Configuration Arrows

(Energy Level Diagram)

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

↑↓

↑

↓

↓

↓

↑

↑

↑

↑

↑↑ ↓ ↓

Silicon

• Rule #2: Only ___ electrons can fit into each orientation.

Example: ___ ___ not ____ 1s 2s 1s

• Rule #3 (Pauli Exclusion Principle): Electrons in the same orientation have ______________ spin.

Example: ___ not ___ 1s 1s

• Rule #4 (Hund’s Rule): “_______________ rule”---> Every “□” in an orbital shape gets an electron before any orientation gets a second e-.

Example: □□□ not □□□ 2p 2p

↓

↓↑ ↑

2↓↑ ↑

opposite

↑ ↑↑

Bus

↑ ↑ ↑ ↑ ↑↓

Electron Configurations

Practice Problems:Write the electron configuration notation for each of the following atoms:

• Hydrogen

• Carbon

• Iron

• Bromine

Shorthand Method: Assumes we already know about the # of □.

• H

• C

• Fe

• Br

Electron Configurations & Properties

• How do electron configurations relate to the chemical and physical properties of an element?

• All elements with the _________ outer shell e- configurations have the ________ properties.

• This means that elements in the same ____________ group have similar properties.

Examples: (1) Li, Na, K, Rb, and Cs all have __ lone “__” e- for their last orbital... (_____, _____, _____, etc.) This makes all of them ___________ reactive. They all react with __________ to produce hydrogen gas.

(2) Ne, Ar, Kr, Xe, and Rn all have the outer energy level completely __________ with electrons...(________, ________, ________, etc.) This makes all of them ______________. They do not produce __________________!

samesimilar

vertical

1 s1s1 2s1 3s1

very water

filled 2s2 2p6 3s2 3p6

4s2 4p6 inertcompounds

More Practice Problems

(1) Which element has its last electron as a 4p5? ___________

(2) Which elements are similar in properties as Bromine? __________

(3) What would the outer shell electron configuration look like for the element underneath Radon, (Rn)?

(4) Which electron is added after 6s2? ________

(5) Which element would “borrow” a 5s electron to get a half-filled “d” sublevel? ___________

(6) What is the shape of the last orbital filled in Calcium, (Ca)? _____

(7) How many electrons are in the last “p-orbital” of Sulfur, (S)? ____

Bromine

F, Cl, I, At

…7s2 5f14 6d10 7p6

4f1

Mo

sphere

4

Electromagnetic Radiation

• Any wave of energy traveling at a speed of ___________ is called electromagnetic radiation.

• There are many types of electromagnetic radiation and each type has a different _______________ and _______________.

• Here are the types of electromagnetic radiation from longest to shortest wave or lowest to highest frequency. These are also in order from lowest to highest energy.

light

frequency wavelength

Electromagnetic Radiation

Electromagnetic Radiation

(1) Radio Waves -- used in __________________

(2) Microwaves-- broadcasts TV signals and used to _____ _______.

(3) Infrared (IR) -- we feel this as _____; _________ & ______ can “see” this.

infrared image of a cat

infrared image of heating pipes under a floor

heat

cook food

communications

snakes owls

IR Mr. TTaken at NASA Goddard Space Center in Maryland

Infrared

Vision

Electromagnetic Radiation

(4) Visible Light -- the only radiation we can detect with our eyes. It can be separated into the colors of the spectrum with a _________.

ROYGBIV(5) Ultraviolet (UV) -- gives you a _____________; _________ can

“see” this; some of this radiation from the sun gets blocked by the ___________ layer

flower photo under normal light flower photo under UV light

prism

sunburn Bees

ozone

Electromagnetic Radiation(6) X-rays -- used in medicine

Ouch!

Electromagnetic Radiation(6) X-rays -- used in medicine

Macy Slade’s shoulder injury CT scan. OH SNAP.

Electromagnetic Radiation

(7) Gamma Rays-- some radioactive substances give it off

• The last type of radiation is sometimes grouped with gamma rays…

(8)_______________Rays -- highest energy radiation; almost all of this radiation from the sun is blocked by the ozone layer. Cosmic rays are

not actually part of the electromagnetic spectrum but still havehigher energy than gamma rays.

Interesting superhero facts:

• Superman has x-ray vision.

• The Incredible Hulk was “created” by an accidental overdose of gamma radiation.

• The Fantastic Four were “created” by cosmic rays.

Cosmic

Chemical Spectra

• Chemists use machines called _________________ to analyze substances.

• All matter absorbs and reflects electromagnetic radiation differently. Our eyes see the visible light that was _____________ by objects.

• Chemists can compare information, called ___________, to previously recorded information to identify substances and predict molecular structure..

spectrometers

spectra

reflected

Chemical Spectra

caffeine

How Light is Produced

• When atoms get hit with energy (by _____________ them with electricity or by ____________ them up), the electrons absorb this energy and __________ to a higher energy level. Figure (a)

• As they immediately fall back down to the “____________ state”, they give off this energy in the form of a particle of ___________ (or other types of electromagnetic radiation) called a _____________. Figure (b)

zapping

heating

jump

ground

light

photon

Energy

Photon

How Light is Produced

• Each photon emitted has a specific ___________ (or frequency).

• The color of the light that is given off depends on how _____ the electron _______ (which depends on how big of a jump it originally made.) The farther the fall, the ___________ energy the photon has.

color

far fell

greater

Figure 11.6: Photons of red and blue light.

How Light is Produced

• Since electrons are located only in certain __________ levels (or orbitals) around the nucleus, only certain specific _________ of light are emitted.

• Scientists use a _________________ to separate these colors into bands of light. These bands of color look like a ______ code of color which is characteristic of that element. No two elements produce the same ______________ of colors. This can be used to distinguish one element from another contained in a sample. (See Fig. 13.11)

energycolor

spectroscopebar

spectrum

Emission Spectrum

Hydrogen Spectrum

Neon Spectrum

How hydrogen produces the four visible photons

All the Photons Produced by Hydrogen

Fluorescence• Fluorescence is a type of ________________ in which the

emission of light is caused by a substance that has absorbed light or other ________________ ____________.

• In most cases the light emitted has a ________ _________ than was absorbed.

• If an electron absorbs more than one photon at once it can emit light at a _________ ___________.

• Fluorescence produces light on a ______________ scale. Which means it happens VERY FAST!

How Fluorescence Works!

luminescence

electromagnetic radiationlower energy

higher energynanosecond

Phosphorescence• Phosphorescence is a type of luminescence in which

the phosphorescent materials ___ ____ __________ re-emit the electromagnetic radiation it absorbs.

• This is due to the electrons going into _________ _________ ______ making it take a longer time for the electrons to get back to the ground state.

What is the difference between Fluorescence and Phosphorescence?

do not immediately

“forbidden”transition states

• The ______ ____ ____ is due to the electrons getting stuck in between energy levels.

• Phosphorescence produces light on a __________ scale. This is still pretty fast to humans but a lot slower compared to a nanosecond scale.

Phosphorescenceslower time scale

millisecond

Chemiluminescence• Chemiluminescence is the emission of light as

a result of a _________ _________. • In a chemiluminescent reaction, the product of the

reaction is in an excited state which then decays into a ground state through either ___________ or ________________.

• Chemiluminescence differs from fluorescence because the excited state is produced from a chemical reaction rather than the _________ of electromagnetic radiation.

chemical reaction

fluorescencephosphorescence

absorption

• Bioluminescence is ______ __________ emitting light by undergoing chemiluminescence.

• For example: jelly fish, glow worms, fireflies, squid, plankton, etc.

Bioluminescence

Ted Talk-Bioluminescence

living organisms

ElectroluminescenceElectroluminescence (EL) is an optical phenomenon

and electrical phenomenon in which a material emits light in response to the passage of an electric current or to a strong electric field

Examples: EL tape and EL wire