BELL RINGER What subatomic particle is not located in the nucleus?
History Atomic History Research Chapter 3 Review Book – Topic 1 Chapter 1
BELL RINGER What are the nucleons (things in the nucleus)?
Quiz • Who did the gold foil experiment? • Who first named an atom? • According to Bohr, where are electrons located? • Draw an atom according to Democritus. • Who discovered the electron?
History - Greeks A. Ancient Greece (2000+ years ago) Democritus - believed that matter could not be continuously divided - Matter consists of small indivisible particles “Atomos” = Atom indivisible - Aristotle did not agree his teacher Particles are in continuous motion Four elements make up all matter and energy Earth, Wind, Water, Fire! No scientific evidence to show this.
History • by 1700s (scientific revolution), all chemists agreed: • on the existence of atoms • that atoms combined to make compounds
Hydrogen Sulfur PbO2 H2S History - Dalton B. Dalton’s Atomic Theory - 1803 1. All matter is composed of small particles which cannot be broken down (atoms) same as Democritus 2. All atoms of the same element are identical in size, mass and properties. Atoms of different elements are different in size, mass and properties 3.Atoms of different element combine in simple ratios to make compounds 4. In chemical reactions, atoms are combined, separated, or rearranged (No atoms are created or destroyed) So at this point, we believe that an atom is like a small solid ball of matter that cannot be split up
Dalton's Amendment's • Some parts of Dalton’s theory were wrong: AMENDMENTS • atoms are divisible into smaller particles (subatomic particles) • atoms of the same element can have different masses (isotopes) • Matter can be lost - Nuclear
History - Thomson C. J.J. Thomson - 1897 Experimented with cathode rays Used electric field to show that cathode rays are negatively charged particles DISCOVORED THE ELECTRON After discovery of the proton, Thomson assumed an atom was a mixture of + and – charged particles, all mixed up + - + - • + - • + - + Plum-Pudding Model
Gold foil Radioactive source Screen Click on me!!! History - Rutherford D.Rutherford Ernest Rutherford wanted to determine what an atom looked like. Fired (+) charged alpha particles at a very thin piece of gold(Gold foil) Put a screen behind the foil to determine what happens to the rays Most of the rays went straight through the foil Some rays deflected A very few rays came straight back
History - Rutherford - - - - - - + Rutherford model Rutherford explained this by stating that a. Atoms have mostly empty space This is why most rays went straight through b. There must be a dense positive center to an atom This is why the positive rays deflected. (Positive rays are repelled by positive charged objects) Later experiments showed that electrons exist in the space between nuclei
Subatomic Particles • includes all particles inside atom • proton • electron • neutron • charge on protons and electrons are equal but opposite • to make an atom neutral, need equal numbers of protons and electrons
Subatomic Particles • number of protons identifies the atom as a certain element • protons and neutrons are about same size • electrons are much smaller
Subatomic Particles • # protons = atomic number • # electrons = # of protons (for now) • # neutrons = mass number– atomic number
Examples p n e 56 23 9 7 Fe Be Na Li 4 3 3 4 26 11 3 12 11 11 4 5 4 26 30 26
BELL RINGER Give the p, n, and e in a neutral atom of Silver.
Some more practice p n e 201 18 17 X Xe Hg Cl 17 17 22 80 121 80 54 77 54 22 26 22
Structure of the Atom • Nucleus: • contains protons and neutrons • takes up very little space • Electron Cloud: • contains electrons • takes up most of space
- - - - - - + Planetary model History - Bohr E. Bohr - looked at the arrangement of electrons 3 2 1 Electrons exist in definite areas around the nucleus Energy levels e- e- e- e- Further from the nucleus, an electron has more energy nucleus Electrons can gain energy and “jump” to higher levels They can then give off the energy as they jump back down Energy levels are numbered 1,2,3,4,5,6,7 • With 1 being closest to the nucleus and having the least amount of energy All atoms have the same types of energy levels
Dr. Wave Mechanical History - Wave Mechanical Model F. Wave Mechanical Model Aka – ‘Electron Cloud’ Modified Bohr’s model Electrons are not in circular orbits, but exist in specific spaces around the nucleus nucleus Pattern is random, unpredictable • most dense near nucleus level level Energy levels contain sublevels
Review of Atoms Dalton Bohr Thompson Rutherford Democritus Wave Mechanical
Electron Location • Located in energy levels outside of the nucleus • The closer to the nucleus = less energy • The farther away from the nucleus = more energy
Electron Location Electrons are located in energy levels or shells.There are a bunch of energy levels and each level can “fit” only a limited number of electrons. 2n2 Where ‘n’ represents the energy level Energy level 1 can have - Energy level 2 can have - Energy level 3 can have - Energy level 4 can have - 2 e- 8 e- 18 e- 32 e-
Bohr Diagrams Gives the location and the number of the p, n, and e. Draw the Bohr diagram for Oxygen: p= n= 8 8 Valence e- = 6
Answer p= n= 9 10 Valence e- = 7
BELL RINGER What did Rutherford contribute to the development of the atom?
Quiz • Ge • Manganese • As • Phosphorus • Ti • Sodium • Cr • Krypton • Be • Boron
The above is an example of a ground state electron configuration (=the configuration on your R.T.’s)
Each electron in an atom has its own distinct amount of energy. Electrons in the first energy level have the lowest potential energy since they are located closest to the nucleus.
p= n= p= n= 10 10 10 10 Excited State e- Configuration for Ne 2-7-1 As an electron gains a specific bunch of energy, the electron “jumps” to a higher energy state (excited state). Ground State e- Configuration for Ne 2-8
p= n= p= n= Gives off 10 10 10 10 Excited State e- Configuration for Ne 2-7-1 How is light produced? Absorbs nrg Releases nrg Ground State e- Configuration for Ne 2-8
When an electron returns from a higher energy state to a lower energy state, a specific amount of energy is given off -->RELEASED
Each elementgives offacertain coloror spectrumofcolors. You can identify unknown elements by the color of light that they give off. Bohr Animation
Ions • So far we have only talked about electrically neutral atoms, atoms with no positive or negative charge on them. • Atoms, however, can have electrical charges – They can gain/lose e-. Some atoms can either gain or lose electrons • The number of protons never changes in an atom.
Ions • If an atom gains electrons, the atom becomes negatively charged. • If the atom loses electrons, the atom becomes positively charged (because the number of positively charged protons will exceed the number of electrons). • An atom that carries an electrical charge is called an ion.
Ions • Listed below are three forms of hydrogen; 2 ions and the electrically neutral form. H+: a positively charged hydrogen ion H-:a negatively charged hydrogen ion H :the hydrogen atom
Ions • Neither the number of protons nor neutrons changes in any of these ions, therefore both the atomic number and the atomic mass remain the same. H+: a positively charged hydrogen ion H-: a negatively charged hydrogen ion H : the hydrogen atom
Ions Identify the number of subatomic particles in the following ions: A.) Na+ B.) F- C.) O-2 p n e 11 9 8 12 10 8 10 10 10
BELL RINGER Which is the electron configuration of an atom in the excited state? • 2-8-2 • 2-8-1 • 2-7-1 • 2-8-3
When subjected to a flame, solutions containing certain metals have characteristic colors corresponding to the energy released when excited electrons return to lower energy levels.
Ions Identify the number of subatomic particles in the following ions: A.) Mg+2 B.) Br- C.) K+ p n e 12 35 19 12 45 20 36 18 10
BELL RINGER Draw the Bohr diagram for a F-1 ion.
What do the Carbon isotopes below have in common? What is different about them? Isotopes • atoms of the same element with different numbers of neutrons • most elements exist as a mixture of isotopes • Disproves Dalton’s theory
Mass Number How many protons do each of the hydrogen atoms below have? • sum of the particles in nucleus • = #p + #n • This is a whole number!!!
Ions/Isotopes PRACTICE PROBLEMS
Relative Atomic Mass • since masses of atoms are so small, it is more convenient to use relative atomic masses instead of real masses • to set up a scale, we have to pick one atom to be the standard • since 1961, the carbon-12 nuclide is the standard and is assigned a mass of exactly 12 amu (=atomic mass unit) REFERENCE TABLES
Relative Atomic Mass • atomic mass unit (amu)- one is exactly 1/12th of the mass of a carbon-12 atom • mass of proton= 1.007276 amu = 1 amu • mass of neutron= 1.008665 amu = 1amu • mass of electron= 0.0005486 amu = 0 amu