Atomic Structure and The Periodic Table Chapter 4 Atomic Structure and The Periodic Table

Ancient Greeks

Democritus’s Greek Philosopher

Democritus’s Atomic Theory Atoms are indivisible and indestructible. Each substance had a different type of atom. Liquid – smooth and round Solid – rough and prickly

Who’s Next? Late 1700’s - John Dalton- England. Teacher- summarized results of his experiments and those of others. Dalton’s Atomic Theory Combined ideas of elements with that of atoms.

John Dalton (1766-1844)

Dalton’s Atomic Theory All matter is made of tiny indivisible particles called atoms. Atoms of the same element are identical, those of different atoms are different. Atoms of different elements combine in whole number ratios to form compounds. Chemical reactions involve the rearrangement of atoms. No new atoms are created or destroyed.

Just how Small is an Atom? Think of cutting a piece of lead into smaller and smaller pieces How far can it be cut? An atom is the smallest particle of an element that retains the properties of that element

J. J. Thomson - English physicist. 1897 Parts of Atoms J. J. Thomson - English physicist. 1897 Made a piece of equipment called a cathode ray tube. It is a vacuum tube - all the air has been pumped out.

J.J. Thompson (1856 – 1940)

Thompson 1897

Thomson’s Experiment Voltage source - + Vacuum tube Metal Disks

Thomson’s Experiment Voltage source - +

Thomson’s Experiment Voltage source - +

Thomson’s Experiment Voltage source - +

- + Thomson’s Experiment Voltage source - + Passing an electric current makes a beam appear to move from the negative to the positive end.

Thomson’s Experiment Voltage source - + Passing an electric current makes a beam appear to move from the negative to the positive end.

Thomson’s Experiment Voltage source - + Passing an electric current makes a beam appear to move from the negative to the positive end.

Thomson’s Experiment Voltage source - + Passing an electric current makes a beam appear to move from the negative to the positive end.

By adding an electric field. Thomson’s Experiment Voltage source By adding an electric field.

Thomson’s Experiment Voltage source + -

Thomson’s Experiment Voltage source + -

Thomson’s Experiment Voltage source + -

Thomson’s Experiment Voltage source + -

Thomson’s Experiment Voltage source + -

Thomson’s Experiment Voltage source + -

Other particles Proton - positively charged pieces 1840 times heavier than the electron – by E. Goldstein Neutron - no charge but the same mass as a proton – by J. Chadwick Where are the pieces?

Ernest Rutherford (1871-1937)

Rutherford

Rutherford’s experiment Ernest Rutherford -English physicist. (1910) Plum Pudding model of the atom. Wanted to see how big they are. Used radioactivity. Alpha particles. Shot them at gold foil.

Rutherford’s experiment When an alpha particle hits a fluorescent screen, it glows. Here’s what it looked like.

Fluorescent Screen Lead block Uranium Gold Foil

What he expected…

Because…..

He thought the mass was evenly distributed in the atom.

Since he thought the mass was evenly distributed in the atom.

What he got…

+ Atom is mostly empty. Small dense, positive piece at center. How he explained it Atom is mostly empty. Small dense, positive piece at center. Alpha particles are deflected by it if they get close enough. +

+

Homework 4-1 Worksheet: 4.1 Due: 10/24/08

Smaller Particles - Quarks Tevatron 1.3 miles

P Quarks N Quarks

Section 10-2 Wrap-up Page: 277 Homework 10-2 Section 10-2 Wrap-up Page: 277 Due: 2/14/06

Matter and Atoms Nucleus e- p+ Protons Electrons n Neutrons

Elements Chemical Symbols Structure of the Atom one type of atom. Substances made up of only one type of atom. Chemical Symbols A shorthand way to write the names of the elements.

# of protons = # of electrons Atomic Number The number of protons in an atom. In a neutral atom # of protons = # of electrons

Atomic mass - # of protons The number of protons and neutrons in an atom. # of neutrons = Atomic mass - # of protons

The average of the atomic mass of all the isotopes of that element. Average Atomic Mass The average of the atomic mass of all the isotopes of that element.  

Atoms of the same element with different number of neutrons. Isotopes Atoms of the same element with different number of neutrons. 1P+ 0N 1e- Protium 1P+ 2N 1e- Tritium 1P+ 1N 1e- Deuterium Average Atomic Mass for H = 1.00794

Atomic Number (# of Protons) 15 30.96376 Phosphorus P Symbol Average Atomic Mass (31) Name

) ) ) 2e- 8e- 5e- Element: Phosphorus # of Protons: 15 15p+ # of Neutrons: 31 –15 = 16 16nº # of Electrons: 15 ) 2e- ) 8e- ) 5e-

Homework 4-2 Worksheet: 4-2 Due: 10/24/08

Bohr 1913 Planetary Model

Energy Levels The possible energies that an electron in an atom can have are called Energy Levels.

Energy Levels 2nd Level Nucleus 1st Level 3rd Level 4th Level

Energy e- Energy

Evidence of Energy levels The energy given off by an electron is in the form of light. Specific element give off specific colors. Spectral Analysis

Evidence of Energy levels

Electron Cloud Model 1926 nucleus

nucleus Electron Cloud Model 1926 Scientist use the electron cloud model to describe the possible locations of electrons around the nucleus.

Atomic Orbitals In each energy level the electrons can have certain orbits that they can take. This a probability of where the electron can be found.

Electron Cloud Model 2nd Level 8e- Nucleus 3rd Level 18e- 1st Level 2e-

Maximum Number of Electrons Atomic Orbitals Energy Level Number of Orbitals Maximum Number of Electrons 1 2 4 8 3 9 18 16 32

Number of Electrons ) 2e- ) 8e- ) 18e- ) 32e-

Electron Configuration Where the electrons are in the orbitals of the atom. The most stable configuration is the one in which the electrons are in orbitals with the lowest energy. Lowest Energy of the electrons is called the Ground State.

) ) ) 2e- 8e- 5e- Element: Phosphorus # of Protons: 15 15p+ # of Neutrons: 31 –15 = 16 16nº # of Electrons: 15 ) 2e- ) 8e- ) 5e-

Homework 4-3 Worksheet: 4-3 Due: 10/28/08 Test: 10/30/08

Democritus’s Atomic Theory Indivisible Indestructible Each substance - different type atom.

Dalton’s Atomic Theory Billiard Ball Model

Dalton’s Atomic Theory Indivisible particles called atoms. Same elements - identical atoms. Whole number ratios - compounds. CO2 CO Chemical reactions … … rearrangement of atoms.

Existence of Charged Particle Thomson’s Experiment Voltage source + - Existence of Charged Particle Positive and Negative

Plum Pudding Model

Rutherford’s Experiment +

Small dense, + piece at center. Atoms have: + Mostly empty. Small dense, + piece at center.

Electrons in Energy Levels Planetary Model Bohr Electrons in Energy Levels

Electron Cloud Model nucleus

Matter and Atoms Nucleus e- p+ Protons Electrons n0 Neutrons

Atomic Number (# of Protons) 14 Si p+ = 14 e- = p+ = 14 n0 = Mass - p+ n0 = 27 – 14 = 13 26.982 Average Atomic Mass (p+ + n0 = 27) AKA - Mass Number Aluminum

p+ = 14 e- = 14 n0 = 13 4 8 2

Atomic Orbital A region of space around the nucleus where an electron is like to be found. Contains 2 electrons.

4 5 8 7 2 2 Ground State Excited State

Atoms of the same element with different number of neutrons. Isotopes Atoms of the same element with different number of neutrons. Cl - 35 Cl - 37 p+ - 17 p+ - 17 n0 - 18 n0 - 20 Average Atomic Mass – 35.453

Element #2 Element #3 Element #1

Element #3: ________________ Color: ____________ Spectrum Element #4: ________________ Color: ____________ Spectrum