unit 1 – atomic structure bravo – 15,000 kilotons

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Unit Unit 1 – Atomic 1 – Atomic Structure Structure Bravo – 15,000 kilotons

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Page 1: Unit 1 – Atomic Structure Bravo – 15,000 kilotons

UnitUnit 1 – Atomic 1 – Atomic StructureStructure

Bravo – 15,000 kilotons

Page 2: Unit 1 – Atomic Structure Bravo – 15,000 kilotons

Chemistry Timeline #1Chemistry Timeline #1B.C. 400 B.C. Democritos 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: Unit 1 – Atomic Structure Bravo – 15,000 kilotons

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: Unit 1 – Atomic Structure Bravo – 15,000 kilotons

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 5: Unit 1 – Atomic Structure Bravo – 15,000 kilotons

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 6: Unit 1 – Atomic Structure Bravo – 15,000 kilotons

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 7: Unit 1 – Atomic Structure Bravo – 15,000 kilotons

Modern Atomic TheoryModern Atomic Theory

Atoms of an element have a characteristic average mass which is unique to that element.

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

All matter is composed of atoms

Atoms of any one element differ in properties from atoms of another element

Page 8: Unit 1 – Atomic Structure Bravo – 15,000 kilotons

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 9: Unit 1 – Atomic Structure Bravo – 15,000 kilotons

Conclusions from the Study Conclusions from the Study of the Electronof the Electron

Cathode rays have identical properties regardless of the element used to produce them. All elements must contain identically charged electrons. Atoms are neutral, so there must be positive particles in the atom to balance the negative charge of the electrons Electrons have so little mass that atoms must contain other particles that account for most of the mass

Page 10: Unit 1 – Atomic Structure Bravo – 15,000 kilotons

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 11: Unit 1 – Atomic Structure Bravo – 15,000 kilotons

Mass of the ElectronMass of the Electron

1909 – Robert Millikan determines the mass of the electron.

The oil drop apparatus Mass of the

electron is 9.109 x 10-31 kg

Page 12: Unit 1 – Atomic Structure Bravo – 15,000 kilotons

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 13: Unit 1 – Atomic Structure Bravo – 15,000 kilotons

Try it Yourself!Try it Yourself!In the following pictures, there is a target hidden by a cloud. To figure out the shape of the target, we shot some beams into the cloud and recorded where the beams came out. Can you figure out the shape of the target?

Page 14: Unit 1 – Atomic Structure Bravo – 15,000 kilotons

The AnswersThe Answers

Target #1 Target #2

Page 15: Unit 1 – Atomic Structure Bravo – 15,000 kilotons

Rutherford’s FindingsRutherford’s Findings

The nucleus is small The nucleus is dense The nucleus is positively charged

Most of the particles passed right through A few particles were deflected VERY FEW were greatly deflected

“Like howitzer shells bouncing off of tissue paper!”

Conclusions:

Page 16: Unit 1 – Atomic Structure Bravo – 15,000 kilotons

Atomic ParticlesAtomic ParticlesParticle Charge Mass # Location

Electron

-1 0 Electron cloud

Proton +1 1 Nucleus

Neutron

0 1 Nucleus

Page 17: Unit 1 – Atomic Structure Bravo – 15,000 kilotons

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 18: Unit 1 – Atomic Structure Bravo – 15,000 kilotons

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 19: Unit 1 – Atomic Structure Bravo – 15,000 kilotons

Atomic NumberAtomic NumberAtomic number (Z) of an element is the number of protons in the nucleus of each atom of that element.

Element # of protons Atomic # (Z)

Carbon 6 6

Phosphorus 15 15

Gold 79 79

Page 20: Unit 1 – Atomic Structure Bravo – 15,000 kilotons

Mass NumberMass NumberMass number is the number of protons and neutrons in the nucleus of an isotope.Mass # = p+ + n0

Nuclide p+ n0 e- Mass #

Oxygen - 10

- 33 42

- 31 15

8 8 1818

Arsenic 75 33 75

Phosphorus 15 3116

Page 21: Unit 1 – Atomic Structure Bravo – 15,000 kilotons

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

nsElectron

sNeutron

sNucleus

Hydrogen–1

(protium)

1 1 0

Hydrogen-2

(deuterium)

1 1 1

Hydrogen-3

(tritium)

1 1 2

Page 22: Unit 1 – Atomic Structure Bravo – 15,000 kilotons

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