benchmark review—important notes

Benchmark Review—important notes

Electron Configuration

Rules for filling orbitalsThere are three rules for filling orbitals.• Aufbau Principle: Electrons always fill the lowest energy levels

first.– Electrons start at the bottom and work their way up.– This also implies that electrons fill orbitals the same way every

time.• Pauli Exclusion Principle: No two electrons with the same

energy characteristics can occupy an orbital at the same time.– One electron must be spin up and the other electron must be spin

down.• Hund’s Rule: When filling multiple orbitals of the same

sublevel (p, d, and f), electrons half-fill the sublevel first before pairing electrons.

Orbital Energy

Order for Filling Orbitals

• 7s 7p 7d 7f• 6s 6p 6d 6f• 5s 5p 5d 5f• 4s 4p 4d 4f• 3s 3p 3d• 2s 2p• 1s

Connections to the Periodic Table• The first two columns of the periodic table are the s-block.• The last six columns of the periodic table are the p-block.• The middle ten columns of the periodic table are the d-block.

Remember that d-block elements fill one energy level late!

After 3p is filled, 4s is filled, then 3d is filled, and then 4p is filled.

• The bottom two rows of the periodic table are the f-block. Remember that f-block elements fill two energy levels late!

After 5p is filled, 6s is filled, then 4f is filled, then 5d is filled, then 6p is filled.

Color-code and label your periodic table!

Density =mass/volume

The Equation Triangle

• Rule #1 – Write the equation so that it has no division lines.

• Rule #2 – What is on the left side of the equal sign goes on the top of the triangle.

• Rule #3 – What is on the right side goes on the bottom of the triangle.

Pure substances vs. Mixtures

Pure Substance: has characteristic physical & chemical properties that can be used to identify it & has a CONSTANT

COMPOSITION

– Element: • Made up of ONE kind of atom (one element from the

periodic table of the elements!)• Cannot be broken down any further• EX: Carbon (C), Nitrogen (N), Oxygen(O), Sodium (Na)

– Compound:• TWO or more atoms chemically combined (molecule)• Can be chemically broken down into individual atoms

(cannot be physically separated)• Definite **ratio of elements** in the compound• EX: Water (H2O), Salt (NaCl), sugar (C6H12O6)

Mixture: Made up of TWO or more substances (the proportions of the ingredients can vary) that can be

physically separated

– Homogeneous Mixture: • Substances are mixed EVENLY throughout• Looks the “same”• EX: Sugar Water, Salt Water, Kool-aid

– Heterogeneous Mixture:• Substances are NOT evenly distributed• Looks “different” throughout• EX: Concrete, Dirt, Pond Water, chocolate chip cookie

• 1. Draw the Lewis Diagram.• 2. Tally up # of bonding regions and lone pairs on central

atom.– double/triple bonds = ONE bonding region

• 3. Shape is determined by the # of bonding regions and lone pairs.

Know the 5 common shapes

How to Determine Molecular Shape

Make a Chart!Shape (Angle)

# of Bonding Regions

# of Lone Pairs

Example Lewis Dot Structure

VSEPR Shape Drawing

1. LINEAR (180°)2 bonding regions0 lone pairs

CO2

3 bonding regions0 lone pairs

BF3

2. TRIGONAL PLANAR (120°)

Exception to the octet rule! – 6 valence electrons!

3. BENT (<120°)2 bonding regions1 lone pair

BENT

<120°

NO2-1


CH4

4. TETRAHEDRAL (109.5°)

3 bonding regions1 lone pair

NH3

5. TRIGONAL PYRAMIDAL (107°)


H2O

6. BENT (104.5°)

Electromagnetic Spectrum

What are the properties of light?

• By 1900 there was enough experimental evidence to convince scientists that light consists of waves.– The amplitude of a wave is the wave’s height from

zero to the crest.– The wavelength, represented by , is the distance

between the crests.– The frequency, represented by , is the number of

wave cycles to pass a given point per unit time.

The Electromagnetic Spectrum

• The product of frequency and wavelength equals a constant (c), the speed of light.

c = – The wavelength and frequency of light are

inversely proportional to each other.– As the wavelength of light increases, the

frequency decreases.

Electromagnetic Radiation

According to the wave model, light consists of electromagnetic waves.– Electromagnetic radiation includes radio waves,

microwaves, infrared waves, visible light, ultraviolet waves, X-rays, and gamma rays.

– All electromagnetic waves travel in a vacuum at a speed of2.998 108 m/s.

The electromagnetic spectrum

The Visible Spectrum

The sun and incandescent light bulbs emit whitelight, which consists of light with a continuous

range of wavelengths and frequencies.– The wavelength and frequency of each color of light

are characteristic of that color.– When sunlight passes through a prism, the different

wavelengths separate into a spectrum of colors.– Red has the longest wavelength and the lowest

frequency in the visible spectrum.

Sample problem: Calculating the wavelength of light

• Use the speed of light to calculate the wavelength of yellow light emitted by a sodium lamp if the frequency of the radiation is 5.09 1014 Hz(5.09 1014 s–1).

(contd.)


• 1. Analyze List the knowns and the unknown. Use the equation c = to solve for the unknown wavelength.

• Knowns– frequency () = 5.09 1014/s– c = 2.998 108 m/s

• Unknown• wavelength () = ? m

(contd.)


2. Calculate Solve for the the unknown.Write the expression that relates the frequency and the wavelength of light.

c =

Rearrange the equation to solve for .

Substitute the known values for and c into the equation and solve.

c

2.998 108m / s

5.09 1014 / s5.89 10 7m

(contd.)


• 3. Evaluate Does the result make sense?– The magnitude of the frequency is much larger than the

numerical value of the speed of light, so the answer should be much lessthan 1.

The quantization of energy

• Planck showed mathematically that the amount of radiant energy (E) of a single quantum absorbed or emitted by a body is proportional to the frequency of radiation ().

E or E = h– The constant (h), which has a value of 6.626 10–34

J · s is called Planck’s constant.– The energy of a quantum equals h.

Sample problem: Calculating the energy of a photon

• Use Planck’s constant to calculate the energy of a photon of microwave radiation with a frequency of 3.20 1011/s.

(contd.)


1. Analyze List the knowns and the unknown. Use the equation E = h to calculate the energy of the photon.

• Knowns– frequency () = 3.20 1011/s– h = 6.626 10–34 J · s

• Unknown• energy (E) = ? J

(contd.)


2. Calculate Solve for the unknown.Write the expression that relates the energy of a photon of radiation and the frequency of the radiation.

E=hv

Substitute the known values for and h into the equation and solve.

E = (6.626 10–34 J · s) (3.20 1011/s) = 2.12 10–22 J

(contd.)


• 3. Evaluate Does the result make sense?– Individual photons have very small energies, so

the answer seems reasonable.

Solids, Liquids, Gases= Phases of Matter

Matter : PhasesStates of matter

• Solid- matter that can not flow and has definite volume.

• Liquid- definite volume but takes the shape of its container (flows).

• Gas- a substance without definite volume or shape and can flow.

States of MatterStates of Matter

Solid

Liquid

Gas

Definite Volume?

YES

YES

NO

Definite Shape?

YES

NO

NO

Temp. increase

Small Expans.

Small Expans.

Large Expans.

Compressible?

NO

NO

YES

Valence Electrons, Reactivity and Oxidation Number

Valence Electrons

• Valence electrons are the number of electrons in the outermost energy

level.

• All elements within a group have the same number of valence electrons

• These electrons are available to be lost, gained, or shared in the formation of chemical compounds.

• Found in the s and p orbitals of the highest energy level.

• Often located in incompletely filled energy levels.

How do I find the number of Valence Electrons?

• To find the number of valence electrons, underline the largest number as often as it occurs and add the superscripts.

• Example: Cl – 1s2, 2s2, 2p6, 3s2, 3p5 – 7 valence electrons

• Example: Mg - 1s2, 2s2, 2p6, 3s2 – 2 valence electrons

• Example: Kr – 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6 – 8 valence electrons

• Example: U – 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6, 5s2, 4d10, 5p6, 6s2, 4f14, 5d10, 6p6, 7s2, 5f4 – 2 valence electrons

Shortcut to finding Valence Electrons!

Group 1 1 valence electronGroup 2 2 valence electronsGroup 13 3 valence electronsGroup 14 4 valence electronsGroup 15 5 valence electronsGroup 16 6 valence electronsGroup 17 7 valence electronsGroup 18 8 valence electrons

WARNING

• there is no shortcut for finding valence electrons for transition or inner-transition metals

• The number of valence electrons for elements from Groups 3-12 can have different values based on the conditions of chemical reactions. This is also true for a small number of the metals in Groups 13-16

Reactivity of groups

• Elements in the same group/family have the same number of valence electrons.

• If you’ll remember from last class, elements in the same group have the similar physical and chemical properties; they react the same way (think alkali metal demo). This has to do with the number of valence electrons!

Oxidation Numbers

Remember that all atoms want to have a full outermost energy level of 8?.....

Oxidation Numbers

The electrical charge resulting from atoms gaining or losing electrons to fill their outermost s and p orbitals.

– All uncombined elements have an oxidation number of zero (0)

– Metals lose electrons and have (+) oxidation numbers; nonmetals gain electrons and have (–) oxidation numbers

– All Noble Gases have an oxidation number of zero (0).

Ions

• Ion – a charged particle or molecule created through the loss or gain of valence electrons

• Cation – positively charged particle or molecule created through the loss of valence electrons as a result of ionization

• Anion – negatively charged particle or molecule created through the gain of valence electrons as a result of electronegativity

Periodic Trends

Summary: periodic trends

15. Explain Periodic Trends In general, how can the periodic trends exhibited by the elements be explained?

15. Explain Periodic Trends In general, how can the periodic trends exhibited by the elements be explained?

The Octet RuleAll elements gain or lose electrons so that

they end up with the same electron configuration as the nearest noble gas.

• The Octet Rule is the driving force for chemical reactions and properties.

• When we say that an atom “wants to” do something, what we really means is that the atom is doing it so that it will become more stable.

Periodic Trends• Periodic Trends – properties that show patterns when

examined across the periodic table.• Atomic Radius – one half the distance between the nuclei of

identical atoms that are bonded together.• Ionization Energy – the energy required to remove one

electron from a neutral atom of an element.– Ion – an atom or group of atoms that has a positive or negative charge – Ionization – the process of forming an ion.

*** Change the electrons, NOT PROTONS!!!! ***– First Ionization Energy –the first electron…– Second Ionization Energy–the second electron…

• Electronegativity – a measure of the ability of an atom in a compound to attract electrons. An uneven concentration of charge.

Radioactive Decay

The Atom

The atom consists of two parts:

1. The nucleus which contains:

2. Orbiting electrons.

protonsneutrons

All matter is made up of elements (e.g. carbon, hydrogen, etc.).

The smallest part of an element is called an atom.

Atom of different elements contain different numbers of protons.

The mass of an atom is almost entirely due to the number of protons and neutrons.

The Atom

XA

Z

Mass number

Atomic number

Element symbol

= number of protons + number of neutrons

= number of protons

The Atom

The atom consists of two parts:

1. The nucleus which contains:

2. Orbiting electrons.

protonsneutrons

All matter is made up of elements (e.g. carbon, hydrogen, etc.).

The smallest part of an element is called an atom.

Atom of different elements contain different numbers of protons.

The mass of an atom is almost entirely due to the number of protons and neutrons.

The Atom

XA

Z

Mass number

Atomic number

Element symbol

= number of protons + number of neutrons

= number of protons

U235

92U

238

92

There are many types of uranium:

Isotopes of any particular element contain the same number of protons, but different numbers of neutrons.

A 235

Z 92

Number of protons 92

Number of neutrons

143

A 238

Z 92

Number of protons 92

Number of neutrons

146

Modes of Decay

Type Symbol Composition Result Strength

Alpha (a) 4He Helium nucleus, 2 neutrons, 2 protons

Nucleus loses mass

Heaviest, therefore the weakest

Beta (b) b- or -1e Electron Neutron into proton

Lighter, stronger

Gamma 0g or g Pure energy;Nucleus gives off extra energy

Strongest

Radioactive decay results in the emission of either:

• an alpha particle (a),

• a beta particle (b),

• or a gamma ray( ).g

Radioactive Decay

An alpha particle is identical to that of a helium nucleus.

It contains two protons and two neutrons.

Alpha Decay

XA

ZY

A - 4

Z - 2+ He

4

2

Alpha Decay

unstable atom

more stable atom

alpha particle

Alpha Decay

Ra226

88

Rn222

86

He4

2

XA

ZY

A - 4

Z - 2+ He

4

2

Ra226

88Rn

222

86+ He

4

2

Alpha Decay

Beta Decay

A beta particle is a fast moving electron which is emitted from the nucleus of an atom undergoing radioactive decay.

Beta decay occurs when a neutron changes into a proton and an electron.

Beta Decay

As a result of beta decay, the nucleus has one less neutron, but one extra proton.

The atomic number, Z, increases by 1 and the mass number, A, stays the same.

Beta Decay

Po218

84

b0

-1

At218

85

XA

ZY

A

Z + 1+ b

0

-1

Beta Decay

Po218

84Rn

218

85+ b

0

-1

Gamma Decay

Gamma rays are not charged particles like a and b particles.

Gamma rays are electromagnetic radiation with high frequency.

When atoms decay by emitting a or b particles to form a new atom, the nuclei of the new atom formed may still have too much energy to be completely stable.

This excess energy is emitted as gamma rays (gamma ray photons have energies of ~ 1 x 10-12 J).

Penetrating Power of Radiation

• The most dangerous form of radiation is gamma radiation. The least dangerous is alpha radiation.

Scientists

John Dalton (1803)

Dalton’s Postulates

1) All elements are composed of tiny indivisible particles called atoms.

2) Atoms of the same element are identical. The atoms of any one element are different from those of any other elements.

3) Atoms of different elements can physically mix together or can chemically combine with one another in simple whole-number ratios to form compounds.

4) Chemical reactions occur when atoms are separated, joined, or rearranged. Atoms of one element, however, are never changed into atoms of another element as a result of a chemical reaction.

Dalton’s Postulates

• We now know that certain parts of this theory are invalid.

• Part 1 – False. Atoms have been split.• Part 2 – Partially False. Some atoms of the

same element have more neutrons. (However, atoms of different elements are different.)

• Part 3 – True!• Part 4 – True!

Dalton’s Model

• Just a tiny ball with no parts inside

J. J. Thomson (1897)

J. J. Thomson• Used a cathode ray tube to shoot an electrical

charge through it.• Saw that the particles were deflected towards

the positive end of the tube.– This must mean that atoms contained a NEGATIVE

charge!• Discovered the ELECTRON.

http://www.youtube.com/watch?v=IdTxGJjA4Jw

http://www.youtube.com/watch?v=RW_zfKOU9uM



http://www.youtube.com/watch?v=RW_zfKOU9uM

Thomson’s Model

• “Plum Pudding” or “Chocolate Chip Cookie Dough” Model.

• A ball of positive charge containing a number of electrons.

Ernest Rutherford (1911)

Ernest Rutherford

• Did the Gold Foil Experiment– Shot alpha (positively charged)

particles at a sheet of gold foil.• Saw that most particles passed

through the foil and some deflected straight back at different angles.

• Means that atoms are mostly empty space but contain a densely packed positive center….– Discovered the NUCLEUS

http://www.youtube.com/watch?v=wzALbzTdnc8&NR=1

http://www.youtube.com/watch?v=5pZj0u_XMbc






Rutherford Model

Nucleus

Empty Space

Electrons

Dense, positively charged nucleus

Surrounded by electrons (mostly empty space)

Niels Bohr (1913)

Niels Bohr

• Electrons travel in definite orbits around the nucleus

• Electrons are found in “energy levels”• AKA Planetary Model

http://www.youtube.com/watch?v=wCCz20JOXXk

http://www.youtube.com/watch?v=wCCz20JOXXk

Bohr Model

Nucleus

Electrons(orbiting the

nucleus)

Average Atomic Mass

65. 39 amu…What does this mean?

• The mass of one atom is not exactly the same as the average mass of many–Ex.) One atom of Zinc 65.39 amu

• This is just the average of the masses of Zn-65, Zn-64, and Zn-66

Calculating Average Atomic Mass–For each isotope:–Multiply percent abundance X mass number

–Then Add together the values for each of the isotopes

Example

• Copper has two naturally occurring isotopes: Copper-63 (69.17%) and copper-65 (30.83%). Calculate the average atomic mass of copper if the relative masses of the isotope are Copper 63 (63 amu) and copper-65 (65 amu).

Properties of Matter

Physical Properties• Can be observed or measured without changing sample’s

composition

Examples: Solubility in waterVolumeLengthColorOdorMelting/Boiling pointMassDensityViscosity

Chemical Property

• Substance’s ability to undergo changes that will change into a new substance

Examples: flammabilitycombustibilityability to react with oxygenability to neutralize acidsionization

Extensive Property

• Depends on the QUANTITY of matter– Examples:

• Mass• Volume• Length

– These Properties change when something gets “fatter”

Intensive Property

• Does NOT depend on the quantity of matter. (It depends on the COMPOSITION of it)– Examples:

• Density • Temperature• Color• Conductivity

– These Properties DON’T change when something gets “fatter”

benchmark review—important notes

Documents