Electron House Where do the electrons live?. Energy Levels & Floors Recall that Bohr was the first scientist to describe electrons using specific energy.

Electron House

Where do the electrons live?

Energy Levels & Floors• Recall that Bohr was the first scientist to describe electrons

using specific energy levels• Bohr proposed that an electron is found only in specific

circular paths, or orbits, around the nucleus• Each possible electron orbit in Bohr’s model has a fixed

energy know as energy levels– The 1st energy level could hold a maximum of 2 electrons– The 2nd energy level could hold a maximum of 8 electrons– The 3rd energy level could hold a maximum of 18 electrons– The 4th energy level could hold a maximum of 32 electrons– Mathematical equations for electrons in energy levels is

2n2 where n is the energy level

Energy Levels & Floors• Your House– The house itself, represents the electron cloud– In your house each floor is a different energy level• On the periodic table each row is an energy level

– Each bedroom represents a sublevel within an energy level. • Sublevels are labeled as s, p, d, or f

– Each bed represents an orbital within the sublevel.• Two people (electrons) can occupy the same bed at

the same time.

What is an Energy level?• energy levels the specific energies an electron in

an atom can have– The number of energy levels equals the period number

• To move from one energy level to another, an electron must gain or lose just the right amount of energy. – A quantum of energy is the amount of energy required

to move an electron from one energy level to another energy level.

• the higher the energy level, the farther it is from the nucleus.

Sleeping Arrangements• Electron will occupy the lowest energy level first– Would you want to walk up steps if you don’t have to.

• One electron will occupy each orbital (bed) before they pair up – Would you want to sleep with your younger brother– A maximum of two electron can occupy each orbital

(each bed)• Think it through…. – How many bed rooms are in the first energy level? – How many beds are available in the first energy level? – So how many electrons can be in the first energy level

total?

Sleeping Arrangements• Second energy level– How many bed rooms– How many bed– How many electrons total can it hold

• Third energy level– How many bed rooms– How many bed– How many electrons total can it hold

• Third energy level– How many bed rooms– How many bed– How many electrons total can it hold

Reading the periodic table!!

Electron’s locations

• Relative locations of electrons described by– Energy level--floors in the electron

house– Sub-level--different rooms on each floor– Orbitals—beds in the room

• Seven energy levels observed to hold electrons

• First energy level closest to nucleus, increasing in distance as subsequent levels neededPeriod = energy level

1234567

Sub-levels• Four known types, additional

proposed* (s, p, d, f, g*, h*)• Each type has a different ‘shape’ or

zone of probability• Number of types of sub-levels

increases as the energy level does – 1st energy level has one sub-level, s only– 2nd energy level has 2 sub-levels, s & p– 3rd energy level has 3 sub-levels, s, p &

d– 4rd energy level has 4 sub-levels, s, p, d

& f

s sub-level

• Spherical in ‘shape’ or zone of probability

• Lowest energy electrons in energy level

• Present in all 7 energy levels• Has 1 orbital (1 bed)

s sub-level

p sub-level

• Dumbbell shaped (2 lobes where electrons have a high probability of being)

• Arranged spatially along x, y, and z axes• Present in all energy levels except 1st

• 3 different orbitals (3 beds)

p sub-level

d sub-levels

• Most have 4 leaf clover shape• Much more complex geometrically

than s, & p • Lobes arranged (mostly) between

axial lines• Present in 3rd energy level and above• 5 different orbital shapes (5 beds)

d sub-levels

f sub-levels

• Even more complex• Present in 4th energy levels and up• 7 different orbital shapes / orientations

f sub-levels

Electron Configuration Rules

• In an atom, electrons and the nucleus interact to make the most stable arrangement possible.

• The ways in which electrons are arranged in various orbitals around the nuclei of atoms are called electron configurations.

• Three rules—the aufbau principle, the Pauli exclusion principle, and Hund’s rule—tell you how to find the electron configurations of atoms

1. Aufbau Principle

• aufbau principle, electrons occupy the orbitals of lowest energy first.

• The orbitals for any sublevel of a principal energy level are always of equal energy.

• within a principal energy level the s sublevel is always the lowest-energy sublevel.

• range of energy levels within a principal energy level can overlap the energy levels of another principal level.

1. Aufbau Principle

2. Pauli Exclusion Principle

• Pauli exclusion principle, an atomic orbital may describe at most two electrons.

• To occupy the same orbital, two electrons must have opposite spins

• the electron spins must be paired. • A vertical arrow indicates an electron and its

direction of spin (↑ or ↓). • An orbital containing paired electrons is written

as

3. Hund’s Rule• Hund’s rule states that electrons occupy orbitals

of the same energy in a way that makes the number of electrons with the same spin direction as large as possible. – three electrons would occupy three orbitals of equal

energy as follows:

Electron Configuration Arrow Diagram

• Arrow Diagrams use boxes and arrows to represent the atomic orbitals and each electrons location in the orbitals

• S sublevel has ONE orbital so it gets 1 box• P sublevel has THREE orbitals so it gets 3 boxes• D sublevel has FIVE orbitals so it gets 5 boxes• F sublevel has SEVEN orbitals so it gets 7 boxes

Arrow Diagrams

• The electrons will fill the lowest energy sub-levels first before moving to the next sub-level (Aufbau Principle)

• Electrons will not pair up until each orbital has one electron in it (Hund’s Rule) and when they pair up they have opposite spin (Pauli Exclusion Principle)

• Note that the sum of the arrows equals the number of electrons in the atom.

Arrow Diagram

• You must label the energy level (1, 2, 3,…..) and the sub-level (s, p, d, f).

• The boxes represent the orbitals (beds)• Use arrows to show each electron

Arrow Diagram

• Hydrogen = 1 electron

• Nitrogen = 7 electrons

• Chlorine = 17 electrons

Arrow Diagram• Remember to follow the three rules– Lowest energy level & sub level first– Don’t pair up until each orbital of same energy has 1

electron– Can only pair if have opposite spins

• It does not matter which way the 1st arrow faces!!!

• Complete Arrow diagram practice

Warm-up : Sketch this into your notes

Electron Configuration• A convenient shorthand method for showing the

electron configuration of an atom– write the energy level and the symbol for every

sublevel occupied by an electron. – indicate the number of electrons occupying that

sublevel with a superscript.– Example: oxygen= 1s22s22p4.

• Note that the sum of the superscripts equals the number of electrons in the atom.

Example

• For Chlorine

• Becomes• 1s2, 2s2, 2p6, 3s2, 3p5

• Use the periodic table like a book and you have to read the elements like words on a page

• You MUST always start on the 1st element.

Electron Configuration Examples

Carbon1s2, 2s2, 2p2

Vanadium1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d3

Noble Gas Electron ConfigurationAbbreviated Electron Configuration

• With larger elements writing out the location of EVERY electron can get a bit cumbersome– W: 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6, 5s2, 4d10, 5p6, 6s2, 4f14,

5d4 • A short hand notation was created using the NOBLE GAS

that comes before the element to abbreviate most of the electrons

• Will still have to show the location of electrons that come after the noble gas

• A noble gas can NOT be its own abbreviation– W the noble gas before it is Xe– W: [Xe] 6s2, 4f14, 5d4

Noble Gas Electron ConfigurationAbbreviated Electron Configuration

Tin (Sn) [Kr] 5s2, 4d10, 5p2

Al [Ne] 3s2, 3p1

Rn [Xe] 6s2, 4f14, 5d10 ,6p6

Ra [Rn] 7s2

Identifying Elements from Configurations• Two methods of using Electron Configuration too

find the element1. Look at the last item in the configuration and match

its location on the periodic table.2. Add up the exponents and see the number of

electrons in the element and match it to the correct element.

Example:1s2, 2s2, 2p6 , 3s2, 3p4

3p4 refers to 3rd period, p-block, 4th element over = S

has 16 electrons so is element # 16 = S

Identifying Elements from Configurations• Example: 1s2, 2s2, 2p6 , 3s2, 3p4, 4s2, 3d10, 4p6, 5s2, 4d4

• 4d4 refers to the 2nd row of the transition metals = Mo• Has 42 electrons = Mo

• Example: [Xe] 6s2, 4f10 • 4f10 refers to 1st row of f-block, 10th element = Dy• [Xe] = 54 e- + 12 e- = 66 e- = Dy

• Practice 1: 1s2, 2s2, 2p6 , 3s2, 3p4, 4s2, 3d10, 4p5,• 4p5 refers to 4th period, p-block ,5th element = Br• 35 electrons = Br

• Practice 2: [Kr] 5s2, 4d7, • 4d7 refers to 2nd row d-block, 7th element = Rh• [Kr]= 36 e- + 9 e- = 45 e- = Rh

Valance Electrons• Valance electrons are the electrons in the

outer energy level of the atom• Valance electrons are the electrons that

participate in forming bonds– Note: Protons determine identity of element– NOTE: electrons determine chemical properties of

element

Valance Electrons• ALL elements: write the electron

configuration and see how many electrons are in HIGHEST energy level. [Kr] 5s2, 4d10, 5p2

– 5th energy level is highest and has 4 electrons so has 4 valance electrons

1s2, 2s2, 2p6, 3s2, 3p5

3rd energy level is highest and has 6 e- so valance electrons = 6

[Kr] 5s2, 4d7, 5th energy level is highest and has 2 e- so valance

electrons = 2

Valance Electrons– Representative Elements (s & p blocks ONLY)

LOOK at 1’s digit in group number– Ca is in group 2 or 2a so it has 2 valance e-– Sb is in group 15 or 5a so it has 5 valance e-– Rn is in group 18 or 8a so it has 8 valance e-– YOU GIVE IT A TRY• In• Sr• S• Fr• I

In = 3 valance e-

Sr = 2 valance e-

S = 5 valance e-

Fr = 1 valance e-

I = 7 valance e-

Quantum Mechanical Model videos• Origins of quantum theory (minuet physics):

http://www.cleanvideosearch.com/media/action/yt/watch?videoId=i1TVZIBj7UA

• Schrodinger’s Cat (minuet physics) http://www.cleanvideosearch.com/media/action/yt/watch?videoId=IOYyCHGWJq4

• Wave/particle duality(Double Slit Experiment and Example in Nature) http://www.cleanvideosearch.com/media/action/yt/watch?videoId=tu57B1v0SzI