1. Atomic Theory Scientists and Models

2. Democritus Coined the term atom to describe the building blocks of matter

3. Antoine Lavosier Carried out experiments using the Scientific Method Father of Chemistry Law of Conservation of Matter Matter can not be created or destroyed

4. John Dalton Developed the 1 st Atomic Model “Marble Like” Developed 1 st Atomic Theory Everything is made of atoms Atoms are indivisible All atoms a an element are identical

5. William Crookes Designed gas tubes (cathode ray tube) which could be filled with different gases. Electrical current could be sent through the tubes.

6. JJ Thomson Atomic Model Atom is positive sphere with embedded negative particles which he named electrons Called the raisin bun model Used Crookes tubes in testing to determine atom had negative particles http://www.youtube.com/watch?v=CsjLYL W_3G0

8. Ernest Rutherford Conducted gold foil experiments Developed an Atomic Theory Nuclear model of the atom, with a positive nucleus and orbiting electrons http://www.youtube.com/watch?v=XBqHkra f8iE

9. Comparison of Thomson and Rutherford

10. Dimetri Mendeleev Design a table of known elements Organized based on common characteristics and repeating patterns of properties

11. E. Henry Mosley He add atomic number rather than atomic mass for order of elements on the Periodic Table. He found that they fell into columns, with elements in the same column showing similar properties.

12. Joseph James Proust Proust played a major role as chemical annalist, establishing the steadiness of the composition of chemical compounds. His work lead to the Law of Fixed Proportions which stated that atoms of different elements combine in a constant ratio to form compound. Proust played a major role as chemical annalist, establishing the steadiness of the composition of chemical compounds. His work lead to the Law of Fixed Proportions which stated that atoms of different elements combine in a constant ratio to form compound.

13. Niels Bohr Refined Rutherford’s Model to include protons and neutrons in nucleus and electrons orbiting in energy levels. Atomic Model Planetary Model positive center with negative electrons orbiting in energy levels Each element has a unique arrangement of electrons which can be determined by energizing the electrons and letting them return to their ground state.

14. Emission Spectra for Elements Emission Spectra for Elements

15. James Chadwick Identified neutrons as the uncharged particles in the nucleus of an atom.

16. Robert Millikan Conducted oil drop experiments which determined the charge on an electron. http://chemistry.umeche.maine.edu/~am ar/fall2004/Millikan.html

17. Erwin Schodinger Studied wave mechanics and used it to describe the behavior of electrons in an atom. Erwin Schrödinger built upon the thoughts of Bohr yet took them in a new direction. He developed the probability function for the Hydrogen. It describes a cloud- like region where the electron is likely to be found. It can not say with any certainty

18. Max Planck Framed the Quantum Theory which says that matter and electrons in particular have wave like and particle like properties. (Bohr and Einstein also had input into Quantum Theory.) Planck also stated that energy traveled in bundles called quanta

19. Louis De Broglie Developed the theory of dual nature of matter – wave like and particle like -which led to Quantum Theory

20. Wolfgang Pauli Pauli Exclusion Principle which states no two electrons can occupy the same place at the same time. This leads to them having opposite spin values.

21. Werner Heisenberg Heisenberg Uncertainty Principle which states that the exact location and acceleration of an electron can not be determined. The best we can do is predict the probable location. This is illustrated in the Electron Cloud Model for atoms.

22. Friedrich Hund Hund’s Rule which states that electrons repel each other and will space themselves as far apart as possible. This means that, electrons will occupy the orbitals singly first, and will only pair up when there are no longer any empty orbitals available in that subshell.

23. Sequence of Atomic Models

24. Electron Arrangement Modern understanding of the structure of the atom provides several methods to represent the arrangement of the electrons in an atom. Modern understanding of the structure of the atom provides several methods to represent the arrangement of the electrons in an atom. The goal is to be able to identify the 'location' of every electron in an atom as to its level, sublevel and orbital. The goal is to be able to identify the 'location' of every electron in an atom as to its level, sublevel and orbital. The location and arrangement of electrons can be described using a number of methods The location and arrangement of electrons can be described using a number of methods Bohr Models Bohr Models Electron Configuration Electron Configuration Noble gas shorthand configuration Noble gas shorthand configuration Orbital Box Diagrams Orbital Box Diagrams Lewis Dot Diagrams Lewis Dot Diagrams

25. Bohr Model of the Atom Based on emission spectra produced by excited electrons falling back to their ground state, Bohr suggested that an electron moves around the nucleus only in certain allowed circular orbits. Based on emission spectra produced by excited electrons falling back to their ground state, Bohr suggested that an electron moves around the nucleus only in certain allowed circular orbits. Bohr models show a nucleus containing protons and neutrons Bohr models show a nucleus containing protons and neutrons The nucleus is surrounded by energy levels which can hold different maximum number of electrons The nucleus is surrounded by energy levels which can hold different maximum number of electrons 1 st level 2e- Example : oxygen 1 st level 2e- Example : oxygen 2 nd level 8e- 2 nd level 8e- 3 rd level 18 e- 3 rd level 18 e- 4 th level 32 e- 4 th level 32 e- 5 th level 32 e- 5 th level 32 e- 6 th level 18 e- 6 th level 18 e- 7 th level 8 e- 7 th level 8 e-

26. Bohr Models Steps to draw a Bohr Model : 1. Determine the number of protons, electrons and neutrons. Protons # and electron # = atomic number Neutrons = Atomic Mass – Atomic Number 2. Draw the nucleus and label #protons and neutrons 3. Draw and fill energy levels until all electrons are place. Remember : level 1 holds 2e- level 2 holds 8e- level 2 holds 8e- level 3 holds 18 e- level 3 holds 18 e- level 4 holds 32 e- level 4 holds 32 e- level 5 hold 32 e- level 5 hold 32 e- level 6 holds 18 e- level 6 holds 18 e- level 7 holds 8 e- level 7 holds 8 e-

27. Electron Configuration Electrons fill in energy levels and sublevels(orbitals) to be as close to the nucleus as possible but as far from each other as possible. This order from closest to farthest is called the Aufbau filling order: Electrons fill in energy levels and sublevels(orbitals) to be as close to the nucleus as possible but as far from each other as possible. This order from closest to farthest is called the Aufbau filling order: 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p Each “s” orbital holds up to 2 electrons, the “ p” orbitals holds up to 6, each “d’ orbital holds up to 10 electrons, and “f” hold up to 14 electrons. Add the number of electrons each orbital holds to the filling order above. Example 1s 2 2s 2 2p 6 …… Another way to show the filling order Write this filling order or diagram on your periodic table.

28. Orbitals An orbital is a possible energy state of an electron. Sometimes it is easier to think visually, an orbital is a volume likely to contain an electron with a specific energy. “s” orbital holds up to 2 electrons “s” orbital holds up to 2 electrons “p” each of the 3 orbitals holds up 2 electrons for a total of to 6 “p” each of the 3 orbitals holds up 2 electrons for a total of to 6 “d” each of the 5 orbitals holds up to 2 electrons for a total of 10 electrons “d” each of the 5 orbitals holds up to 2 electrons for a total of 10 electrons “f” each of 7 orbitals holds up to 2 electrons for a total of 14 electrons.

29. Summary Chart Subshell Summary Value of nSubshell Name Number of orbitals in the subshell Orbital Shape (Centered at the Nucleus) Maximum # Electrons 11s1Sphere2 2 2s 2p 1313 Sphere Double teardrop 2626 3 3s 3p 3d 135135 Sphere Double teardrop Four leafed clover 2 6 10 44s 4p 4d 4f 13571357 Sphere Double teardrop Four leafed clover Sea urchin? Or some other really lumpy thing. 2 6 10 14

30. Writing an electron configuration To designate the electron configuration we : 1. Identify the number of electrons 2. Use the Aufbau filling order to fill in the level number (1-7) the level number (1-7) the letter of the sublevel (s, p, d, f) the letter of the sublevel (s, p, d, f) a superscript number to represent thenumber of electrons contained in the sublevel. a superscript number to represent thenumber of electrons contained in the sublevel. Ex. Argon has 18 electrons write is electron configuration

31. Quantum Numbers Quantum numbers is sort of like a finger print: even though you have the same basic form as other human beings, you are unique and you have a unique finger print. Your finger print isn’t what makes you an individual, but it is a way to differentiate you from others. A set of quantum numbers doesn’t make an orbital, but it allows us to distinguish among them. But a set of quantum numbers is more than just an identifier. Their values give us information about the shape and orientation of electrons. It is related to the electron configuration The primary quantum number tells the energy level ( n) = 1-7 The second quantum number tell the shape of the sublevel (s,p,d,f). The third part of the quantum number tells the number of electrons and their orientation.

32. Quantum number example Oxygen ELECTRON CONFIGURATION : 1s 2 2s 2 2p 4 Quantum number : 2p 4 number of electrons energy level orbital shape The quantum number also corresponds to an elements position on the periodic table. Oxygen in on the 2 nd row in the P block and it is the 4 th element

33. Electron Configuration, Quantum numbers and the Periodic Table - Groups 1 and 2 of the periodic table are referred to as the s block because these elements have outer electrons in an s orbital. - Groups 13 through 18 are referred to as the p block because these elements have outer electrons in a p subshell. - Groups 3 through 12 are referred to as the d block and the inner transition elements are f block.

34. Noble Gas Configuration An abbreviated method for electron configurations uses a set of brackets [ ] around the chemical symbol of a noble gas. Noble gases are used because they have full s and p sublevels and are at the end of a row on the periodic table. An abbreviated method for electron configurations uses a set of brackets [ ] around the chemical symbol of a noble gas. Noble gases are used because they have full s and p sublevels and are at the end of a row on the periodic table. A shorter version of an electron configuration can be written based on a "noble gas core".This refers to the electrons within the atom which have the same electron configuration as the nearest noble gas of lower atomic number. The core electrons are the inner electrons which do not determine properties or behavior. A shorter version of an electron configuration can be written based on a "noble gas core".This refers to the electrons within the atom which have the same electron configuration as the nearest noble gas of lower atomic number. The core electrons are the inner electrons which do not determine properties or behavior. The electron configuration for potassium is: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 The electron configuration for potassium is: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 Argon is the noble gas that precedes potassium on the periodic table so Potassium has an argon core plus 4s 1 so it is written [Ar] 4s 1 [Ar] 4s 1

35. Orbital BoxDiagrams Another way to identify the location of each electron is via an orbital diagram. This notation uses a box to represent the orbital and an arrow to represent the electron. Electrons fill in the orbital boxes following the Aufbau filling order. Each box can hold 2 electrons Electrons fill in one in each orbital box before placing a second electron into an orbital( Hund’s Rule). If 2 electrons are in the same orbital the have opposite spins ↑↓ ( Pauli Exclusion Principle). The “S” sublevel is draw as a single box which can hold up to 2e-, “P” sublevels are shown as 3 connected boxes holding a max of 6 e-, “D” sublevels have 5 orbital boxes, and “F” sublevels have 7 orbital boxes holding a maximum of 10 and 14 e- respectively.

36. Orbital Diagram Example Carbon has 6 electrons. Its orbital diagram is shown at the right. Try to draw the orbital diagram for Sulfur The link below is to a tutorial on electron configuration and orbital dot structures. http://intro.chem.okstate.edu/AP/2003SanAntonio/Chapter7 /Lec111000.html

37. Lewis Dot Structure Lewis dot structure are yet another method to show electron arrangement. The chemical symbol for the atom is surrounded by a number of dots corresponding to the number of electrons in their outermost energy level (valence electrons). The ‘s’ electrons are drawn at the top, and the ‘p’ electrons are drawn around the symbol clockwise, one at each position before doubling up. The element Sodium has 1 valance electron. Its Lewis dot structure is ● Na Sulfur has 6 valance electrons its’ Lewis dot structure is ●● ● S ●● ●

38. Methods to represent the arrangement of the electrons in an atom of Oxygen Methods to represent the arrangement of the electrons in an atom of Oxygen Bohr Models → Bohr Models → Electron Configuration Electron Configuration 1s 2 2s 2 2p 4 Quantum number 2p 4 Quantum number 2p 4 Orbital Box Diagram → Orbital Box Diagram → Lewis Dot Structure for oxygen Lewis Dot Structure for oxygen ●● ●● ● O ●● ● O ●● ● Bohr model of oxygen

39. A couple of other ideas Another way to remember Aufbau filling order Another way to remember Aufbau filling order Labeled Periodic Table with sublevels Labeled Periodic Table with sublevels