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Atoms, Molecules, and Atoms, Molecules, and Ions Ions

Atoms, Molecules, and Ions

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Atoms, Molecules, and Ions. Chemistry Timeline #1. B.C. 400 B.C. Demokritos and Leucippos use the term "atomos”.  2000 years of Alchemy. 1500's Georg Bauer: systematic metallurgy Paracelsus: medicinal application of minerals. 1600's - PowerPoint PPT Presentation

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Page 1: Atoms, Molecules, and Ions

Atoms, Molecules, and Atoms, Molecules, and IonsIons

Page 2: Atoms, Molecules, and Ions

Chemistry Timeline #1Chemistry Timeline #1B.C. 400 B.C. Demokritos and Leucippos use the term "atomos”

1500's Georg Bauer: systematic metallurgy Paracelsus: medicinal application of minerals

1600'sRobert Boyle:The Skeptical Chemist. Quantitative experimentation, identification of elements

1700s'Georg Stahl: Phlogiston Theory Joseph Priestly: Discovery of oxygen Antoine Lavoisier: The role of oxygen in combustion, law of conservation of mass, first modern chemistry textbook

2000 years of Alchemy

Page 3: Atoms, Molecules, and Ions

Chemistry Timeline #2Chemistry Timeline #2

1800's Joseph Proust: The law of definite proportion (composition) John Dalton: The Atomic Theory, The law of multiple proportions Joseph Gay-Lussac: Combining volumes of gases, existence of diatomic molecules Amadeo Avogadro: Molar volumes of gases Jons Jakob Berzelius: Relative atomic masses, modern symbols for the elements Dmitri Mendeleyev: The periodic table J.J. Thomson: discovery of the electron Henri Becquerel: Discovery of radioactivity

1900's Robert Millikan: Charge and mass of the electron Ernest Rutherford: Existence of the nucleus, and its relative size Meitner & Fermi: Sustained nuclear fission Ernest Lawrence: The cyclotron and trans-uranium elements

Page 4: Atoms, Molecules, and Ions

Laws• Conservation of Mass• Law of Definite Proportion –

– compounds have a constant composition.

– They react in specific ratios by mass.• Multiple Proportions-

– When two elements form more than one compound, the ratios of the masses of the second element that combine with one gram of the first can be reduced to small whole numbers.

Page 5: Atoms, Molecules, and Ions

Proof• Mercury has two oxides.

– One is 96.2 % mercury by mass, the other is 92.6 % mercury by mass.

• Show that these compounds follow the law of multiple proportion.

• Speculate on the formula of the two oxides.

Page 6: Atoms, Molecules, and Ions

Dalton’s Atomic Theory Dalton’s Atomic Theory (1808)(1808)

Atoms cannot be subdivided, created, or destroyed Atoms of different elements combine in simple whole-number ratios to form chemical compounds In chemical reactions, atoms are combined, separated, or rearranged

All matter is composed of extremely small particles called atoms Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties

John Dalton

Page 7: Atoms, Molecules, and Ions

Modern Atomic TheoryModern Atomic TheorySeveral changes have been made to Dalton’s theory.

Dalton said:

Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties

Modern theory states:Atoms of an element have a

characteristic average mass which is unique to that element.

Page 8: Atoms, Molecules, and Ions

Modern Atomic Theory #2Modern Atomic Theory #2

Dalton said:

Modern theory states:

Atoms cannot be subdivided, created, or destroyed

Atoms cannot be subdivided, created, or destroyed in ordinary chemical reactions. However, these changes CAN occur in nuclear reactions!

Page 9: Atoms, Molecules, and Ions

Atomic ParticlesAtomic ParticlesParticle Charge Mass (kg) Location

Electron

-1 9.109 x 10-31 Electron cloud

Proton +1 1.673 x 10-27 Nucleus

Neutron

0 1.675 x 10-27 Nucleus

Page 10: Atoms, Molecules, and Ions

The Atomic The Atomic ScaleScale

Most of the mass of the atom is in the nucleus (protons and neutrons) Electrons are found outside of the nucleus (the electron cloud) Most of the volume of the atom is empty space

“q” is a particle called a “quark”

Page 11: Atoms, Molecules, and Ions

About Quarks…About Quarks…Protons and neutrons are NOT fundamental particles.Protons are made of two “up” quarks and one “down” quark.Neutrons are made of one “up” quark and two “down” quarks.

Quarks are held together by “gluons”

Page 12: Atoms, Molecules, and Ions

IsotopesIsotopes Isotopes are atoms of the same element having different masses due to varying numbers of neutrons.

Isotope Protons

Electrons

Neutrons

Nucleus

Hydrogen–1

(protium)

1 1 0

Hydrogen-2 (deuterium

)

1 1 1

Hydrogen-3 (tritium)

1 1 2

Page 13: Atoms, Molecules, and Ions

Atomic Atomic MassesMasses

Isotope Symbol Composition of the nucleus

% in nature

Carbon-12

12C 6 protons 6 neutrons

98.89%

Carbon-13

13C 6 protons 7 neutrons

1.11%

Carbon-14

14C 6 protons 8 neutrons

<0.01%

Atomic mass is the average of all the naturally isotopes of that element.Carbon = 12.011

Page 14: Atoms, Molecules, and Ions

MoleculesMolecules

Two or more atoms of the same or different elements, covalently bonded together.

Molecules are discrete structures, and their formulas represent each atom present in the molecule.

Benzene, C6H6

Page 15: Atoms, Molecules, and Ions

Covalent Network Covalent Network SubstancesSubstances

Covalent network substances have covalently bonded atoms, but do not have discrete formulas.

Why Not??

Graphite Diamond

Page 16: Atoms, Molecules, and Ions

IonsIonsIonsIons Cation: A positive ion Cation: A positive ion

• MgMg2+2+, NH, NH44++

Anion: A negative ion Anion: A negative ion ClCl, SO, SO44

22

Ionic Bonding: Force of attraction Ionic Bonding: Force of attraction between oppositely charged ions. between oppositely charged ions.

Ionic compounds form Ionic compounds form crystalscrystals, so their , so their formulas are written empirically (lowest formulas are written empirically (lowest whole number ratio of ions).whole number ratio of ions).

Page 17: Atoms, Molecules, and Ions

Periodic Table with Group Names

Page 18: Atoms, Molecules, and Ions

This slide contains This slide contains classified material and classified material and

cannot be shown to high cannot be shown to high school students. Please school students. Please

continue as if everything is continue as if everything is normal.normal.

Page 19: Atoms, Molecules, and Ions

Discovery of the ElectronDiscovery of the ElectronIn 1897, J.J. Thomson used a cathode ray tube to deduce the presence of a negatively charged particle.

Cathode ray tubes pass electricity through a gas that is contained at a very low pressure.

Page 20: Atoms, Molecules, and Ions

Thomson’s Atomic Thomson’s Atomic ModelModel

Thomson believed that the electrons were like plums embedded in a positively charged “pudding,” thus it was called the “plum pudding” model.

Page 21: Atoms, Molecules, and Ions

Rutherford’s Gold Foil Rutherford’s Gold Foil ExperimentExperiment

Alpha particles are helium nuclei Particles were fired at a thin sheet of gold foil Particle hits on the detecting screen (film) are recorded

Page 22: Atoms, Molecules, and Ions
Page 23: Atoms, Molecules, and Ions

The Puzzle of the AtomThe Puzzle of the Atom Protons and electrons are attracted to each other because of opposite charges

Electrically charged particles moving in a curved path give off energy

Despite these facts, atoms don’t collapse

Page 24: Atoms, Molecules, and Ions

c = C = speed of light, a constant (3.00 x 108 m/s)

= frequency, in units of hertz (hz, sec-1)

= wavelength, in meters

Electromagnetic radiation Electromagnetic radiation propagates through space as a wave propagates through space as a wave moving at the speed of light.moving at the speed of light.

Page 25: Atoms, Molecules, and Ions

Types of electromagnetic radiation:Types of electromagnetic radiation:

Page 26: Atoms, Molecules, and Ions

Long Wavelength

= Low Frequency

= Low ENERGY

Short Wavelength

= High Frequency

= High ENERGY

Wavelength TableWavelength Table

Page 27: Atoms, Molecules, and Ions

The Wave-like ElectronThe Wave-like Electron

Louis deBroglie

The electron propagates through space on an energy

wave. To understand the atom, one must

understand the behavior of

electromagnetic waves.

Toupee?

Page 28: Atoms, Molecules, and Ions

The Great The Great Niels Bohr (1885 - 1962)

Page 29: Atoms, Molecules, and Ions

…produces all of the colors in a continuous spectrum

Spectroscopic analysis of the visible Spectroscopic analysis of the visible spectrum…spectrum…

Page 30: Atoms, Molecules, and Ions

…produces a “bright line” spectrum

Spectroscopic analysis of the Spectroscopic analysis of the hydrogen spectrum…hydrogen spectrum…

Page 31: Atoms, Molecules, and Ions

This produces bands of light with definite wavelengths.

Electron Electron transitionstransitionsinvolve jumps of involve jumps of definite amounts definite amounts ofofenergy.energy.

Page 32: Atoms, Molecules, and Ions

                                         

                   

Bohr Model Energy Levels

Page 33: Atoms, Molecules, and Ions

Schrodinger Wave EquationSchrodinger Wave Equation

22

2 2

8dh EV

m dx

Equation for probabilityprobability of a single electron being found along a single axis (x-axis)Erwin Schrodinger

Page 34: Atoms, Molecules, and Ions

Heisenberg Uncertainty Heisenberg Uncertainty PrinciplePrinciple

You can find out where the electron is, but not where it is going.

OR…

You can find out where the electron is going, but not where it is!

“One cannot simultaneously determine both the position and momentum of an electron.”

Werner Heisenberg

Page 35: Atoms, Molecules, and Ions
Page 36: Atoms, Molecules, and Ions

Quantum NumbersQuantum Numbers

Each electron in an atom has a unique set of 4 quantum numbers which describe it.

Principal quantum number Angular momentum quantum number Magnetic quantum number Spin quantum number

(n)(l)

(m)(s)

Page 37: Atoms, Molecules, and Ions

Principal Quantum NumberPrincipal Quantum NumberGenerally symbolized by n, it denotes the shell (energy level) in which the electron is located.

Number of electrons that can fit in a shell:

2n2

Page 38: Atoms, Molecules, and Ions

Angular Momentum Quantum Angular Momentum Quantum NumberNumber

The angular momentum quantum number, generally symbolized by l, denotes the orbital (subshell) in which the electron is located.

l =3f

Page 39: Atoms, Molecules, and Ions

Magnetic Quantum NumberMagnetic Quantum NumberThe magnetic quantum number, generally symbolized by m, denotes the orientation of the electron’s orbital with respect to the three axes in space.

Page 40: Atoms, Molecules, and Ions

Assigning the NumbersAssigning the Numbers The three quantum numbers (n, l, and m) are integers. The principal quantum number (n) cannot be zero. n must be 1, 2, 3, etc. The angular momentum quantum number (l ) can be any integer between 0 and n - 1. For n = 3, l can be either 0, 1, or 2. The magnetic quantum number (ml) can be any integer between -l and +l. For l = 2, m can be either -2, -1, 0, +1, +2.

Page 41: Atoms, Molecules, and Ions

Principle, angular momentum, and Principle, angular momentum, and magnetic quantum numbers: magnetic quantum numbers: nn, , ll, and , and mmll

Page 42: Atoms, Molecules, and Ions

Pauli Exclusion PrinciplePauli Exclusion Principle

No two electrons in an atom can have the same four quantum numbers.

Wolfgang Pauli

Page 43: Atoms, Molecules, and Ions

Spin Quantum NumberSpin Quantum NumberSpin quantum number denotes the behavior (direction of spin) of an electron within a magnetic field.

Possibilities for electron spin:

1

2

1

2

Page 44: Atoms, Molecules, and Ions

Orbital shapes are defined as the surface that contains 90% of the total electron probability.

An orbital is a region within an atom where thereAn orbital is a region within an atom where thereis a probability of finding an electron. This is a is a probability of finding an electron. This is a probability diagram for the s orbital in the probability diagram for the s orbital in the first first energy level…energy level…

Page 45: Atoms, Molecules, and Ions

Orbitals of the same shape (s, for instance) grow larger as n increases…

Nodes are regions of low probability within an orbital.

Sizes of Sizes of ss orbitals orbitals

Page 46: Atoms, Molecules, and Ions

Orbitals in outer energy levels DO penetrate into lower energy levels.

This is a probability Distribution for a 3s orbital.

What parts of the diagram correspond to “nodes” – regions of zero probability?

Penetration #1

Page 47: Atoms, Molecules, and Ions

The s orbital has a spherical shape centered around the origin of the three axes in space.

s orbital shape

Page 48: Atoms, Molecules, and Ions

There are three peanut-shaped p orbitals in each energy level above n = 1, each assigned to its own axis (x, y and z) in space.

PP orbital shape orbital shape

Page 49: Atoms, Molecules, and Ions

Things get a bit more complicated with the five d orbitals that are found in the d sublevels beginning with n = 3. To remember the shapes, think of:

…and a “peanut with a donut”!

d orbital shapes

“double peanut”

Page 50: Atoms, Molecules, and Ions

Shape of f orbitalsShape of f orbitals

Things get even more complicated with the seven f orbitals that are found in the f sublevels beginning with n = 4. To remember the shapes, think of:

Flower

Page 51: Atoms, Molecules, and Ions

Orbital filling tableOrbital filling table

Page 52: Atoms, Molecules, and Ions

Element Configuration notation

Orbital notation Noble gas notation

Lithium 1s22s1 ____ ____ ____ ____ ____ 1s 2s 2p

[He]2s1

Beryllium 1s22s2 ____ ____ ____ ____ ____ 1s 2s 2p

[He]2s2

Boron 1s22s2p1 ____ ____ ____ ____ ____ 1s 2s 2p

[He]2s2p1

Carbon 1s22s2p2 ____ ____ ____ ____ ____ 1s 2s 2p

[He]2s2p2

Nitrogen 1s22s2p3 ____ ____ ____ ____ ____

1s 2s 2p

[He]2s2p3

Oxygen 1s22s2p4 ____ ____ ____ ____ ____ 1s 2s 2p

[He]2s2p4

Fluorine 1s22s2p5 ____ ____ ____ ____ ____ 1s 2s 2p

[He]2s2p5

Neon 1s22s2p6 ____ ____ ____ ____ ____ 1s 2s 2p

[He]2s2p6

Page 53: Atoms, Molecules, and Ions
Page 54: Atoms, Molecules, and Ions

Electron configuration of the Electron configuration of the elements of the first three elements of the first three

seriesseries

Page 55: Atoms, Molecules, and Ions

Irregular confirmations of Cr and CuIrregular confirmations of Cr and Cu

Chromium steals a 4s electron to half fill its 3d sublevel

Copper steals a 4s electron to FILL its 3d sublevel

Page 56: Atoms, Molecules, and Ions

0% 0% 0%0%0%

1. energy is emitted2. energy is absorbed3. no change in energy

occurs4. light is emitted5. none of these

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24 25 26 27 28 29 30 31 32

Page 57: Atoms, Molecules, and Ions

gamma ra

ys

micr

owaves

radio w

aves

infra

red ra

dia...

x-ray

s

0% 0% 0%0%0%

1. gamma rays2. microwaves3. radio waves4. infrared radiation5. x-rays

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24 25 26 27 28 29 30 31 32

Page 58: Atoms, Molecules, and Ions

2 5 10 18 6

0% 0% 0%0%0%

1. 22. 53. 104. 185. 6

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24 25 26 27 28 29 30 31 32

Page 59: Atoms, Molecules, and Ions

0% 0% 0%0%0%0%

n l m s

1. 1 1 0 ½2. 3 0 0 –½3. 2 1 –1 ½4. 4 3 –2 –½5. 4 2 0 ½

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24 25 26 27 28 29 30 31 32

Page 60: Atoms, Molecules, and Ions

1s22s2

2p63s23p...

1s22s2

2p63s23p...

1s23s2

2p63s23p...

1s22s2

2p63s23p...

none of these

0% 0% 0%0%0%

1. 1s22s22p63s23p64s23d104p65s24d105p15d10

2. 1s22s22p63s23p64s23d104d104p1

3. 1s23s22p63s23p64s24d104p65s25d105p1

4. 1s22s22p63s23p64s23d104p65s24d105p1

5. none of these

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24 25 26 27 28 29 30 31 32

Page 61: Atoms, Molecules, and Ions

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24 25 26 27 28 29 30 31 32

Page 62: Atoms, Molecules, and Ions

Periodicity

Page 63: Atoms, Molecules, and Ions

Atomic Radius = half the distance between two nuclei of a diatomic molecule.

}Radius

Page 64: Atoms, Molecules, and Ions

Influenced by three factors. Energy Level

› Higher energy level is further away. Charge on nucleus

› More charge pulls electrons in closer. Shielding

› Layers of electrons shield from nuclear pull.

Page 65: Atoms, Molecules, and Ions

The electron on the outside energy level has to look through all the other energy levels to see the nucleus

Page 66: Atoms, Molecules, and Ions

The electron on the outside energy level has to look through all the other energy levels to see the nucleus.

A second electron has the same shielding.

Page 67: Atoms, Molecules, and Ions

As we go down a group

Each atom has another energy level,

So the atoms get bigger.

HLi

Na

K

Rb

Page 68: Atoms, Molecules, and Ions

As you go across a period the radius gets smaller.

Same energy level. More nuclear charge. Outermost electrons are closer.

Na Mg Al Si P S Cl Ar

Page 69: Atoms, Molecules, and Ions

Table of Table of

Atomic Atomic RadiiRadii

Page 70: Atoms, Molecules, and Ions

Cations form by losing electrons. Cations are smaller that the atom they

come from. Metals form cations. Cations of representative elements

have noble gas configuration.

Page 71: Atoms, Molecules, and Ions

Anions form by gaining electrons. Anions are bigger that the atom they

come from. Nonmetals form anions. Anions of representative elements

have noble gas configuration.

Page 72: Atoms, Molecules, and Ions

Atomic Number

Ato

mic

Radiu

s (n

m)

H

Li

Ne

Ar

10

Na

K

Kr

Rb

Page 73: Atoms, Molecules, and Ions

The amount of energy required to completely remove an electron from a gaseous atom.

Removing one electron makes a +1 ion.

The energy required is called the first ionization energy.

Page 74: Atoms, Molecules, and Ions

The second ionization energy is the energy required to remove the second electron.

Always greater than first IE. The third IE is the energy required to

remove a third electron. Greater than 1st of 2nd IE.

Page 75: Atoms, Molecules, and Ions

Symbol First Second ThirdH

HeLiBeBCNOF Ne

1312 2731 520 900 800 1086 1402 1314 1681 2080

5247 7297 1757 2430 2352 2857 3391 3375 3963

11810 14840 3569 4619 4577 5301 6045 6276

Page 76: Atoms, Molecules, and Ions

The greater the nuclear charge the greater IE.

Distance from nucleus increases IE Filled and half filled orbitals have lower

energy, so achieving them is easier, lower IE.

Shielding

Page 77: Atoms, Molecules, and Ions

As you go down a group first IE decreases because

The electron is further away. More shielding.

Page 78: Atoms, Molecules, and Ions

All the atoms in the same period have the same energy level.

Same shielding. Increasing nuclear charge So IE generally increases from left to

right. Exceptions at full and 1/2 fill orbitals.

Page 79: Atoms, Molecules, and Ions

Firs

t Io

niz

ati

on e

nerg

y

Atomic number

He He has a greater IE

than H. same shielding greater nuclear

charge H

Page 80: Atoms, Molecules, and Ions

Firs

t Io

niz

ati

on e

nerg

y

Atomic number

H

He Li has lower IE than H more shielding further away outweighs greater nuclear

charge

Li

Page 81: Atoms, Molecules, and Ions

Firs

t Io

niz

ati

on e

nerg

y

Atomic number

H

He Be has higher IE than Li same shielding greater nuclear charge

Li

Be

Page 82: Atoms, Molecules, and Ions

Firs

t Io

niz

ati

on e

nerg

y

Atomic number

H

He B has lower IE than Be same shielding greater nuclear charge By removing an electron we

make s orbital half filled

Li

Be

B

Page 83: Atoms, Molecules, and Ions

Firs

t Io

niz

ati

on e

nerg

y

Atomic number

H

He

Li

Be

B

C

Page 84: Atoms, Molecules, and Ions

Firs

t Io

niz

ati

on e

nerg

y

Atomic number

H

He

Li

Be

B

C

N

Page 85: Atoms, Molecules, and Ions

Firs

t Io

niz

ati

on e

nerg

y

Atomic number

H

He

Li

Be

B

C

N

O

Breaks the pattern because removing an electron gets to 1/2 filled p orbital

Page 86: Atoms, Molecules, and Ions

Firs

t Io

niz

ati

on e

nerg

y

Atomic number

H

He

Li

Be

B

C

N

O

F

Page 87: Atoms, Molecules, and Ions

Firs

t Io

niz

ati

on e

nerg

y

Atomic number

H

He

Li

Be

B

C

N

O

F

Ne Ne has a lower

IE than He Both are full, Ne has more

shielding Greater distance

Page 88: Atoms, Molecules, and Ions

Firs

t Io

niz

ati

on e

nerg

y

Atomic number

H

He

Li

Be

B

C

N

O

F

Ne Na has a lower

IE than Li Both are s1

Na has more shielding

Greater distance

Na

Page 89: Atoms, Molecules, and Ions

Firs

t Io

niz

ati

on e

nerg

y

Atomic number

Page 90: Atoms, Molecules, and Ions

Full Energy Levels are very low energy. Noble Gases have full orbitals. Atoms behave in ways to achieve noble

gas configuration.

Page 91: Atoms, Molecules, and Ions

Affinity tends to increase across a period

Affinity tends to decrease as you go down in a period

Electrons farther from the nucleus experience less nuclear attraction

Some irregularities due to repulsive forces in the relatively small p orbitals

Electron AffinityElectron Affinity - the energy change - the energy change associated with the addition of an electronassociated with the addition of an electron

Page 92: Atoms, Molecules, and Ions

Table of Electron AffinitiesTable of Electron Affinities

Page 93: Atoms, Molecules, and Ions
Page 94: Atoms, Molecules, and Ions

The tendency for an atom to attract electrons to itself when it is chemically combined with another element.

How fair it shares. Big electronegativity means it pulls the

electron toward it. Atoms with large negative electron

affinity have larger electronegativity.

Page 95: Atoms, Molecules, and Ions

The further down a group the farther the electron is away and the more electrons an atom has.

More willing to share. Low electronegativity.

Page 96: Atoms, Molecules, and Ions

Metals are at the left end. They let their electrons go easily Low electronegativity At the right end are the nonmetals. They want more electrons. Try to take them away. High electronegativity.

Page 97: Atoms, Molecules, and Ions

Ionization energy, electronegativityElectron affinity INCREASE

Page 98: Atoms, Molecules, and Ions

Atomic size increases, shielding constant

Ionic size increases

Page 99: Atoms, Molecules, and Ions

Another Way to Look at Ionization Energy

Page 100: Atoms, Molecules, and Ions

Yet Another Way to Look at Ionization Energy

Page 101: Atoms, Molecules, and Ions
Page 102: Atoms, Molecules, and Ions

Summary of Periodic Summary of Periodic TrendsTrends