Chemistry Warm Up Some Dimensional Analysis Review.

PLEASE SHOW YOUR WORK USING CONVERSION FACTORS AND DIMENSIONAL ANALYSIS 1. If 6.02 x 10 23 atoms of carbon have a mass of 12.0 grams, what the mass of 1.51 x 10 23 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 10 2 grams?

Chemistry Warm Up:

Periodic Table Scavenger Hunt

1. 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 don’t 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.* i.*

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.

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

Dalton- Indivisible Atom J.J.Thomson discovers subatomic particle “Plum pudding,” model QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.

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Development of Atomic Models

Rutherford’s 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 can’t 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 (n=1, n=2…) •Energy sublevels = different shapes •The first energy level has one sublevel: 1

s 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

p y

Atomic Orbitals

•The forth energy level has four sublevels, 4s 4p 4d orbitals And seven 4f orbitals QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.

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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 1s 1

3 rules:

Pauli Exclusion Principal

- two electrons per orbital (one spin up, one spin down)

Boron has 5 electrons 1s 2 2s 2 2p 1

3 rules:

Hund’s rule

- In orbitals with equal energy levels, arrange spin to maximize electrons with the same spin

1s 2 2s 2 2p 3 Nitrogen has 7 electrons

Hund’s Rule: Separate the three 2p elecrons into the three available 2p orbitals to maximize the electrons with the same spin.

1s 2

Conceptual Problem p135

Electron Configuration for Phosphorus (atomic # = 15) 2s 2 2p 6 3s 2 3p 3

1s 2

Practice Problem 8a p135

Electron Configuration for Carbon (atomic number = 6) 2s 2 2p 2

1s 2

Practice Problem 8b p135

Electron Configuration for Argon (atomic # = 18) 2s 2 2p 6 3s 2 3p 6

Electron Configuration for Nickel (atomic # = 28) 1s 2

Practice Problem 8c p135

2s 2 2p 6 3s 2 3p 6 3d 8 4s 2

1s 2

Practice Problem 9a p135

Electron Configuration for Boron (atomic # = 5) 2s 2 2p 1 How many unpair ed electro ns?

1

1s 2

Practice Problem 8c p135

Electron Configuration for Silicon (atomic # = 14) 2s 2 2p 6 3s 2 3p 2 How many unpair ed electro ns?

2

Copper atomic number=29 1s

Exceptions to the Aubau Rule

2 2s 2 2p 6 3s 2 3p 6 3d 9 4s 2 This is the expected electron configura tion

Copper atomic number=29 1s

Exceptions to the Aubau Rule

2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 1 Half This is the actual electron configura tion.

means stealing an electron from a nearby sublevel

Chromium atomic number=24 1s

Exceptions to the Aubau Rule

2 2s 2 2p 6 3s 2 3p 6 3d 4 4s 2 This is the expected electron configura tion

Chromium atomic number=24 1s

Exceptions to the Aubau Rule

2 2s 2 2p 6 3s 2 3p 6 3d 5 4s 1 Half This is the actual electron configura tion.

means stealing an electron from a nearby sublevel

5.3 Physics and the Quantum Mechanical Model

Or, “How do they get all those colors of neon lights?”

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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 10 wavelength decreases 8 So, as the frequency of light increases, the

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 10 14 Hz (Hz = s -1 ) Wavelength • frequency = 3.00x10

8 m/s Wavelength = 3.00x10

-8 m/s / frequency Wavelength = 3.00x10

8 m/s / 5.10x10

Wavelenght = 5.88 x 10

-7 m

14 s -1

Wavelength of Light p140 #14:What is the wavelength of radiation if the frequency is 1.50x10

of red light?

Wavelength = 3.00x10

Wavelength = 3.00x10

8 8 13 Hz (Hz = s Wavelength • frequency = 3.00x10

8 m/s / 1.50x10

-1 m/s 13 ) m/s / frequency s ?

Is this longer or shorter than the wavelenght -1 Wavelength = 2.00 x 10

-5 m Longer than red light

which 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 = 3.00x10

8 m/s frequency = 3.00x10

8 m/s / wavelength frequency = 3.00x10

8 m/s / 5.00x10

-8 m Frequency = 6.00 x 10

15 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