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Chemistry Warm Up Some Dimensional Analysis

Review.

- PLEASE SHOW YOUR WORK USING CONVERSION FACTORS

AND DIMENSIONAL ANALYSIS - If 6.02 x 1023 atoms of carbon have a mass of

12.0 grams, what the mass of 1.51 x 1023 atoms

of carbon atoms. Hint set up the equality that

you know. Make two conversion factors and use one

to solve the problem. Check your work using

dimensional analysis. - 2. How many atoms are there in sample of carbon

that weighs 30.0grams? - 3. How many atoms are there in a sample that

weighs 3.60 x 102 grams?

Chemistry Warm Up Periodic Table Scavenger Hunt

- The periodic table is arranged by atomic number,

not by atomic mass. Find a sequence of three

elements that are arranged by atomic number but

not by atomic mass. - 2. Find three elements whose symbols dont seem

to have anything to do with their names. Write

the name and the symbol for each. - 3. There are two rows at the bottom of the

periodic table. Use the atomic number to figure

out where they fit in to the periodic table. - 4. What would the periodic table look like if

those two rows were inserted in order of their

atomic number? Make a sketch.

Chapter5.1 Models of the Atom

California State Science Standards Chemistry 1.

The periodic table displays the elements in

increasing atomic number and shows how

periodicity of the physical and chemical

properties of the elements relates to atomic

structure. As a basis for understanding this

concept g. Students know how to relate the

position of an element in the periodic table to

its quantum electron configuration and to its

reactivity with other elements in the table. i.

Students know the experimental basis for the

development of the quantum theory of atomic

structure and the historical importance of the

Bohr model of the atom.

Chapter5.1 Models of the Atom

Development of Atomic Models Rutherfords Model

- Dense central Nucleus
- Electrons orbit like planets
- Atom mostly empty space
- Does not explain chemical behavior of atoms

The Bohr Model

- Electrons orbit the nucleus
- Specific circular orbits
- Quantum energy to move from one level to

another

The Bohr Model

- Energy level like rungs of the ladder
- The electron cannot exist between energy levels,

just like you cant stand between rungs on a

ladder - A quantum of energy is the amount of energy

required to move an electron from one energy

level to another

The Bohr Model

Energy level of an electron analogous to the

rungs of a ladder

But, the rungs on this ladder are not evenly

spaced!

Quantum Mechanical Model

- Energy quantized comes in chunks.
- A quantum is the amount of energy needed to move

from one energy level to another. - Since the energy of an atom is never in between

there must be a quantum leap in energy. - 1926 Erwin Schrodinger equation described the

energy and position of electrons in an atom

Quantum Mechanical Model

Things that are very small behave differently

from things big enough to see. The quantum

mechanical model is a mathematical solution It

is not like anything you can see.

Quantum Mechanical Model

Has energy levels for electrons. Orbits are not

circular. It can only tell us the probability of

finding an electron a certain distance from the

nucleus.

Atomic Orbitals

Energy levels (n1, n2) Energy sublevels

different shapes The first energy level has one

sublevel 1s orbital -spherical

Atomic Orbitals

The second energy level has two sublevels, 2s

and 2p

There are 3 p-orbitals

Atomic Orbitals

The third energy level has three sublevels, 3s

3p

And 5 3d orbitals

Atomic Orbitals

The forth energy level has four sublevels, 4s

4p

4d orbitals And seven 4f orbitals

Atomic Orbitals The principal quantum number

(energy level) equals the number sublevels

5.2 Electron Arrangement in Atoms

Electron Configuration Electrons and nucleus

interact to produce most stable

arrangement Lowest energy configuration

3 rules

Aufbau Principle Electrons fill the lowest energy

orbitals first

Hydrogen has 1 electron

1s1

3 rules

Pauli Exclusion Principal- two electrons per

orbital (one spin up, one spin down)

Boron has 5 electrons

1s2

2s2

2p1

3 rules

Hunds rule- In orbitals with equal energy

levels, arrange spin to maximize electrons with

the same spin

1s22s22p3

Nitrogen has 7 electrons

Hunds Rule Separate the three 2p elecrons into

the three available 2p orbitals to maximize the

electrons with the same spin.

Conceptual Problem p135

Electron Configuration for Phosphorus (atomic

15)

1s2

2s2

2p6

3s2

3p3

Practice Problem 8a p135

Electron Configuration for Carbon (atomic number

6)

1s2

2s2

2p2

Practice Problem 8b p135

Electron Configuration for Argon (atomic 18)

1s2

2s2

2p6

3s2

3p6

Practice Problem 8c p135

Electron Configuration for Nickel (atomic 28)

1s2

2s2

2p6

3s2

3p6

4s2

3d8

Practice Problem 9a p135

Electron Configuration for Boron (atomic 5)

1s2

2s2

2p1

How many unpaired electrons? 1

Practice Problem 8c p135

Electron Configuration for Silicon (atomic 14)

1s2

2s2

2p6

3s2

3p2

How many unpaired electrons? 2

Exceptions to the Aubau Rule

Copper atomic number29

1s2

2s2

2p6

3s2

3p6

4s2

3d9

This is the expected electron configuration

Exceptions to the Aubau Rule

Copper atomic number29

1s2

2s2

2p6

3s2

3p6

4s1

3d10

Half-filled and filled sublevels are more stable,

even if it means stealing an electron from a

nearby sublevel

This is the actual electron configuration.

Exceptions to the Aubau Rule

Chromium atomic number24

1s2

2s2

2p6

3s2

3p6

4s2

3d4

This is the expected electron configuration

Exceptions to the Aubau Rule

Chromium atomic number24

1s2

2s2

2p6

3s2

3p6

4s1

3d5

Half-filled and filled sublevels are more stable,

even if it means stealing an electron from a

nearby sublevel

This is the actual electron configuration.

5.3 Physics and the Quantum Mechanical Model

Or, How do they get all those colors of neon

lights?

Goals

Describe the relationship between wavelength and

frequency of light Identify the source of atomic

emission spectra Explain how frequency of

emitted light are related to changes in electron

energies Distinguish between quantum mechanics

and classical mechanics

Quick review of wave terminology

Amplitude height of wave Wavelength distance

between crests Frequency number of crests to

pass a point per unit of time

Light waves

Amplitude height of wave Wavelength distance

between crests Frequency number of crests to

pass a point per unit of time

For light, the product of frequency and

wavelength speed of light, c Frequency

Wavelength 3.00 x 108 So, as the frequency of

light increases, the wavelength decreases

Electromagnetic Spectrum

Visible light is only part of the electromagnetic

spectrum

Wavelength of Light p140

Sample Problem What is the wavelength of yellow

light from a sodium lamp if the frequency is 5.10

x 1014 Hz (Hz s-1)

Wavelength frequency 3.00x108m/s Wavelength

3.00x10-8 m/s / frequency Wavelength

3.00x108m/s / 5.10x1014 s-1 Wavelenght 5.88 x

10-7 m

Wavelength of Light p140

14What is the wavelength of radiation if the

frequency is 1.50x1013 Hz (Hz s-1)? Is this

longer or shorter than the wavelenght of red

light? Wavelength frequency

3.00x108m/s Wavelength 3.00x108 m/s /

frequency Wavelength 3.00x108m/s / 1.50x1013

s-1 Wavelength 2.00 x 10-5 m Longer than red

lightwhich if between 10-6 and 10-7 m

Wavelength of Light p140

15 What is the frequency of radiation if the

wavelength is 5.00x10-8 Hz (Hz s-1) In what

range of the electromagnetic specrum is

this? Wavelength frequency 3.00x108m/s frequen

cy 3.00x108 m/s / wavelength frequency

3.00x108m/s / 5.00x10-8m Frequency 6.00 x 1015

s-1 ultraviolet

Atomic Spectra

When atoms absorb energy, Electrons move to

higher energy levels. When electrons return to

the lower energy level, they emit light Each

energy level produces a certain frequency of

light resulting in an emission spectrum

Atomic Spectra

Emission spectra are like a fingerprint of the

element We know what stars are made of by

comparing their emission spectra to that of

elements we find on earth

Explanation of Atomic Spectra

Emission spectra like a fingerprint of the

element We know what stars are made of by

comparing their emission spectra to that of

elements we find on earth