Notes CH 5Electron Configurations

telling electrons where they can go!!

Electrons.. Where are they?

And why do we need to know?The chemical behavior of an element is determined by the number of electrons and how they are arranged.

Bohr’s modelHelped explain why elements give off certain colors of light (excited electrons jumping to lower energy levels)Electrons travel in specific energy “orbits” but not in between them.

1st2nd

3rdElectron can be here

But not here

Review…Bohr’s model of the atom

Each level has a certain number of e-1st = 22nd = 83rd = 18 (or 8)4th = 32 (or 18 or 8)5th = 32 (or 18 or 8)6th = 18 (or 8)7th = 8**Note= last level cannot have more than 8 valence e-

nucleus Energy levels

Bohr models of various atoms.

1. Draw (or write) the Bohr sequence for Calcium (20)

2. Give the # of valence electrons (last level)

3. Tell if will lose e- (like metals, have less than 4) or gain e- (like non-metals, have more than 4) or metalloids (either gain or lose)

4. Give the isotope symbol

Bohr models of various atoms.

1. Draw (or write) the Bohr sequence for Bromine

2. Give the # of valence electrons (last level)

3. Tell if will lose e- (like metals, have less than 4) or gain e- (like non-metals, have more than 4) or metalloids (either gain or lose)

4. Give the isotope symbol

Example

For all the element Bromine (35):1) Draw (or write) the Bohr sequence

2) Give the # of valence electrons 3) Tell if will lose e- (like metals) or gain

e- (like non-metals)

4) Give the ion symbol and charge

2 – 8 – 18 - 7

7

Will gain one electron

80 35 Br -1

QuestionWhy do elements give off different colors of light when heated? (need to know for LAB on Friday)

Some of the electrons (ground state) gain enough energy from the heat to jump up to a higher energy level (excited state). They are unstable here so they jump back to a lower level and give off the energy gained as photons. The photon’s energy determines the frequency (and color) of light.

Flame tests and SpectraEach element has a characteristic pattern of light that it emits.This can be used as a “fingerprint” for identification.

Niels Bohr’s Atomic model

Yes! It’s Bohring!

http://videos.howstuffworks.com/hsw/5787-niels-bohrs-atomic-model-video.htm

Assignment = Simple atomic models

1. a. Bohr’s modelb. isotope symbolc. charge

For these elements: S, As, Sr, Ar, Cl, Ag

2. Pg 145 # 10, 12-14 (show details for calculations)

Modern views of the AtomElectrons can act as particles and sometimes as waves (dual nature)Electrons travel in paths that look like clouds. The size and shape of these depend on how much energy the electrons have.The 4 quantum numbers describe the location of the electrons:Principal QN (symbol “n”) refers to the number of energy levels and indicates the relative size and energies in the atomic orbitals.

Secondary or angular QN (symbol “l” ) indicates the sublevel (s, p, d, or f)Magnetic QN (symbol “m”) indicates the orbital the electron is in (px, py or pz)

Spin QN (symbol “s” ) indicates the direction the electron is spinning (left or right)There are 7 energy levels divided into different sublevels which are divided into orbitals. An orbital is the space where two electrons travel. They have the shape of the sublevel but different orientations.Sublevels:s = 2 e- max p = 6 e- d = 10 e- f = 14 e-

“s” =

“p” =

Shape of d

Shape of f

Mind Blowing!!Just imagine an atom with for example 92 electrons like Uranium. All are whizzing around the nucleus at the speed of light in different shaped paths.

Just read

Video orbitals!http://www.youtube.com/watch?v=K-jNgq16jEY&feature=related

Electron configuration (long form)

This gives MORE information about predicting properties. The placement of an elements electrons is written as:

1s2, 2s2, 2p6, 3s2, 3p6

These add up to total # of e-4p6

4th Energy level 6 electrons

Sublevel p

How many total electrons?

What element is it?

There are rules!Aufbau rule: Electrons occupy the lowest energy orbitals first.Hund’s rule: States that single electrons must occupy separate orbitals before pairing up.Pauli Exclusion Principle: No two electrons in an atom have all 4 quantum numbers the same. One quantum number must be different. Aka SPIN!

The “Arrow” DiagramElectrons arrange themselves in orbitals of increasing energy.

This is on page 160.

s = 2 p = 6 d= 10 f = 14

Examples:

N

Al

K

Br

Ag

Take sulfur for example. It has an atomic number of 16, so it has 16 electrons. Let’s put these in order.

1s2, 2s2, 2p6, 3s2, 3p4

Valence e-? _____ on level ____How many e- lost/gained? _______Charge of ion? _______Check it! it should be in group 6 and on period 3 ……is it?

Practice

1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p3

Write the electron configuration (long form) for:Arsenic ____ electrons

And for arsenic’s ion? (As3-)

Practice

1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6 , 5s2 , 4d9

Write the electron configuration (long form) for:Silver ____ electrons

And for silver ion? Hint: it loses one e-)

HWpg. 160 #21 & 22 and WS

BellringerTurn in HW pg 160 (21, 22)A) Write the long-form electron configuration for V (23)

B) tell how many valence e- it hasC) give the ionic charge

1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d3 ; 2; 2+

Bellringer 21. Which QN symbol means “main

energy level”?2. Which 4 symbols means “sublevel”?3. Write the long configuration for Se

(34)

4. How many valence electrons are there?

5. What will the charge of the ion be?

n

62-

s, p, d, f

1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p4

Electron configuration Shorthand version (Noble

gas version)Ex Silver = [1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6 ], 5s2 , 4d9

Take the previous Noble Gas and substitute[Kr], 5s2 , 4d9

Or do directly from PT……

Copy or memorize… or Google

“f” before “d” d (n-1) and f (n-2)

→ ← 7p →

More….

1. Oxygen

2. And O2- ??

3. Arsenic

4. Aluminum

5. And Al3+ ??

6. Europium

More Practice

Fe 3+

F1-

Na1+

N 3-

Rules? …..What rules?1. Electrons can behave as a particle but

also have wavelike behavior (dual-nature by DeBroglie)

2. Electrons will be in the lowest available energy position first. (Aufbau rule)

3. Electrons will be in separate orbitals (same energy) before pairing up. (Hund’s rule)

4. Electrons will orient themselves to have opposite spins if in same orbital. (Pauli rule)

What??? Let’s try applying this…..

Orbital diagramsWe use boxes to indicate the orbitals

And arrows to indicate each electron

1s 2s 2p 3s

4d

Practice

Let’s do oxygen (8e-)

So…it has 2 unpaired electrons to use for bonding with other elements.And now aluminum (13 e-)

1s 2s 2p 3s 3p

2s 2p 3s 3p1s

More

Let’s do Neon (10 e-)

And now chlorine (18 e-)

1s 2s 2p 3s 3p

2s 2p 3s 3p1s

AndVanadium

Selenium

Bellringer

1. Turn in Homework

2. What is the long form electron configuration for sulfur? See

pg 160

3. How many valence electrons does it have and on what level?

4. How many e- does it need to have a complete valence level?

5. What is the short form and orbital diagram for Te (52)?

6. What is wrong with this? [Ar] 4s2, 3d6 , 4p3

Practicea) Bohr modelb) long formc) Short formd) Orbital diagrame) Valence e-

Pd Ge Pb

Homeworka) Bohr modelb) long formc) Short formd) Orbital diagrame) Valence e-

At (85) K(19) Se (34) P(15)

Videohttp://www.youtube.com/watch?v=xH1k1dtgiVY

Electron Dot DiagramsOnly show valence electronsExamples:

Assignment

Pg 167 (Glencoe)# 81, 85, 86, 87, 90

To turn in!Write the: a) short electron configuration.b) # of valence e c) # e- lost/gainedd) charge of ion

1. iodine 5. helium2. hafnium 6. boron3. francium 7. yttrium4. xenon 8. tin

Exit slip

For the element Phosphorous (P) and Bromine (Br)

Write the: a) short electron configuration.b) # of valence e c) # e- lost/gainedd) charge of ione) orbital diagram

Bellringer1. What is the long form electronWhich

symbol means “main energy level”?2. Which symbol means “sublevel”?3. Which symbol means “number of

electrons”?4. How many valence electrons are

there?5. What will the charge of the ion be?

[Ar] 4s2, 3d10 , 4p3

3 or 4

52, 3 or 10

3-

s, p or d

Bellringer

1. What symbol is used in orbital diagrams to show one electron?

2. What rule says that electrons will occupy the lowest energy orbitals first?

3. Who first stated that electrons can behave both as a particle and as a wave?

4. What do we call the distance on a wave for a complete cycle?

5. What do we call the height (energy) of a wave?

An arrow

Aufbau

DeBroglie

Wavelength

Amplitude

To turn in!Write the: a) Bohr sequence (ex 2-8-3)b) long electron configuration.c) # of valence e d) # e- lost/gained, charge of ion

1. Palladium 5. Argon2. Indium 6. Molybdenum3. Gadolinium 7. Polonium4. Dysprosium 8. Radium

EMR (electromagnetic radiation)

All wavelengths = from gamma rays (very short=high energy) to radio and TV (long=low energy).All types of EMR travel at the speed of lightAre emitted when excited electrons jump to lower energy levels.A “piece” or quantum of EMR is called a photon.

Review EMR waves

or crests

A Solving problems Show all your work, write the equation and be sure to indicate your units c= v and E photon = h v

speed of light is c=3.00 x 108 m/s Planck’s constant is h = 6.626 x 10-34J s

1) What is the wavelength of electromagnetic radiation with a frequency of 8.77 x 1014 Hz?

2) What is the frequency of light that has a wavelength of 400. nm?

MoreCalculate the frequency for yellow light See handout

600 nm = 600 x -9 m

Calculate the frequency for a bar-code laser.

660 nm = 660 x 10 -9 m

Calculate the energy for an X-ray photon (3.88 x 10 17 Hz)

5.00 x 10 14 1/s

4.55 x 10 14 1/s

2.57 x 10 -16 J