2. Unit #4 Electron Configuration / Periodic Table

3. 1)Remember: Atoms are: Nucleus dense positively charged center of the atom. Accounts for the mass of an atom. Contains both protons and neutrons Proton positively charged particle (equal to +1) in the nucleus with a mass of 1 AMU. Approximately equal to 1.67 * 10 -24 g. Nucleus dense positively charged center of the atom. Accounts for the mass of an atom. Contains both protons and neutrons Proton positively charged particle (equal to +1) in the nucleus with a mass of 1 AMU. Approximately equal to 1.67 * 10 -24 g.

4. Neutron an uncharged particle in the nucleus; same mass as a proton. Electron negatively charged particle (equal to -1) that orbits the nucleus with an insignificant mass. Approximately equal to 9.11 * 10 -28 g. Neutron an uncharged particle in the nucleus; same mass as a proton. Electron negatively charged particle (equal to -1) that orbits the nucleus with an insignificant mass. Approximately equal to 9.11 * 10 -28 g.

5. 2)Remember: location and types of electrons Valence electrons in the outer most "shell". The maximum number of these for any atom is 8. (We will later learn that they fill the "s" & "p" sublevels in the highest energy levels). Core any electron not considered a valence electron. In between the nucleus and the outermost "shell". Valence electrons in the outer most "shell". The maximum number of these for any atom is 8. (We will later learn that they fill the "s" & "p" sublevels in the highest energy levels). Core any electron not considered a valence electron. In between the nucleus and the outermost "shell".

6. Electron Cloud area surrounding the nucleus where the electrons can be found. Both valence and core electrons are here. This area is negatively charged. Analogous to clouds surrounding the earth. Electron Cloud area surrounding the nucleus where the electrons can be found. Both valence and core electrons are here. This area is negatively charged. Analogous to clouds surrounding the earth.

7. Electron Configuration Now we will learn how the electrons are arranged in an atom.

8. Remember the various atomic theories we learned about in unit #3. Considering those ideas, what do you think the numbers (and sometimes letters) on the left-hand edge of the periodic chart represent ?

9. Energy Level represents the most probable distance of the electron from the nucleus of the atom. It is always represented as a positive whole number; 1-7. Electrons in the first energy level have the lowest amount of energy; electrons in the seventh energy level have the most energy. (Sometimes: the energy levels are represented by the letters (from lowest to highest energy) K, L, M, N, O, P, Q.) Energy Level represents the most probable distance of the electron from the nucleus of the atom. It is always represented as a positive whole number; 1-7. Electrons in the first energy level have the lowest amount of energy; electrons in the seventh energy level have the most energy. (Sometimes: the energy levels are represented by the letters (from lowest to highest energy) K, L, M, N, O, P, Q.)

10. Ground state most stable, lowest energy position of an electron. Excited state any position of electron except the ground state. Less stable, higher energy. Ground state most stable, lowest energy position of an electron. Excited state any position of electron except the ground state. Less stable, higher energy.

11. Lighting and the chemistry behind the characteristic colors of some types of light bulbs:

12. Law of conservation of energy energy is neither created nor destroyed, it just changes forms. Law of conservation of energy energy is neither created nor destroyed, it just changes forms.

13. Examples The sun ’ s energy is captured by chlorophyll and other accessory pigments in plants. The energy is stored in the plant in the form of carbohydrates. After millions of years, these stored carbohydrates can become fossil fuels. Humans can burn these fossil fuels to "create" energy. (Heat water to make steam.) The sun ’ s energy is captured by chlorophyll and other accessory pigments in plants. The energy is stored in the plant in the form of carbohydrates. After millions of years, these stored carbohydrates can become fossil fuels. Humans can burn these fossil fuels to "create" energy. (Heat water to make steam.)

14. Example continued… The steam spins turbines that in turn spin generators. The generators make an electric current. When the electric current is passed through a "gas" this excites the electrons. The steam spins turbines that in turn spin generators. The generators make an electric current. When the electric current is passed through a "gas" this excites the electrons.

15. Example continued… When the electrons drop back down to their ground state they emit light of a characteristic color. He=yellow light Ar=lavenderlight Kr=white light Xe=blue light Ne=orange / red Na=yellow / orange H=red When the electrons drop back down to their ground state they emit light of a characteristic color. He=yellow light Ar=lavenderlight Kr=white light Xe=blue light Ne=orange / red Na=yellow / orange H=red

16. How it works

17. 1p+  ENERGY IN  “LIGHT” OUT 

18. Electron Configuration Particular distribution of electrons among available "sublevels". Often represented as: 1s 2 2s 2 2p 3 (this as you will later learn is the electron configuration of Nitrogen.) Sublevel Indicates the shape of the orbital in which the electrons move. (These are components of a given energy level.) Represented by the letters: s, p, d, and f.

19. Space orbital A highly probable location about a nucleus in which an electron may be found. The number of space orbitals determines the sublevel. Sublevels are composed of “ Space Orbitals ”. The type of sublevel is determined by the number of space orbitals. A highly probable location about a nucleus in which an electron may be found. The number of space orbitals determines the sublevel. Sublevels are composed of “ Space Orbitals ”. The type of sublevel is determined by the number of space orbitals.

20. All "s", have 1 space orbital. Represented by: All "p", have 3 space orbitals. Represented by: All "d", have 5 space orbitals. Represented by: All "f", have 7 space orbitals. Represented by:

21. All valence electrons will ALWAYS be located in ONLY the "s" and "p" sublevels.

22. Octet Rule In most cases, chemical bonds form so that each atom has an octet of electrons in their valence shells. What is an Octet?Eight of something

23. Pauli Exclusion Principle Rule stating that each space orbital can hold a maximum of 2 electrons and they must have opposite spins. The first electron in a space orbital is represented by drawing an upward pointing arrow in the space orbital. Example: The second electron in a space orbital is represented by drawing a downward pointing arrow in the same space orbital. The opposite spins are represented by the arrows with opposite directions. Example:

24. If more than one space orbital is in a sublevel; then Hund's Rule will apply.

25. Hund's Rule When electrons occupy the same sublevel (s, p, d, or f), to achieve the lowest energy arrangement (most desirable) of the electrons place the electrons into separate space orbitals, one at a time until all space orbitals have one electron with all their spins parallel (going the same direction), before pairing up any of the electrons.

27. Aufbau Principle Scheme used to reproduce the electron configuration of the ground states of atoms by successfully filling subshells with electrons in a specific order. Remember: electron configuration: particular distribution of electrons among available "sublevels".

28. Aufbau Principle (con ’ t.) Also known as the: The "Order of electron fill". The "Building up order". The "Diagonal Rule".

29. Electrons fill orbitals in a reasonably definite order starting with the lowest energy level. You must be able to use (and reproduce) the chart that will follow. It will make determination of electron placement much easier.

31. To use: Simply start at "1s" and fill the sublevel according to Hund's Rule. When a given sublevel is full, follow the arrow forward. When you reach the head of an arrow, drop down to the arrow below and continue to fill sublevels as per Hund's Rule.

32. Exceptions to the above "filling pattern" exist. We will focus only on those within the first 36 elements. As we encounter these exceptions, we will discuss them since they are often representative of other elements within the same group.

33. 1st. Exception Carbon (and several other Group IV elements.) 1s 2 2sp 3

34. Orbital Diagram Notation showing how the orbitals of a subshell are occupied by electrons. This follows Hund ’ s rule. Example: Notation showing how the orbitals of a subshell are occupied by electrons. This follows Hund ’ s rule. Example: Remember electron configurations are represented as: 1s 2 2s 2 2p 3

35. Electron Dot Notation Shows the Element symbol and the valence electrons. Also called "Lewis Symbols".

36. Symbol- represents the nucleus and the core electrons. "Dots"- represent the valence electrons and are shown as eitherpaired or unpaired.

37. Represents the first valence "p" space orbital Represents the third valence "p" space orbital Represents the second valence "p" space orbital Represents valence "s" space orbitals

38. A few periodic short cuts.

39. Series / Period horizontal rows on the periodic chart. All elements in the same series or period are in the same energy level.

40. Family / Group vertical columns on the periodic chart All elements in the same family or group have the same number of valence electrons.

41. Collective group names: 1. Halogens 2. Noble Gases 1. Halogens 2. Noble Gases

42. Halogens - Very reactive non-metals found in group VII. They have the general formula "X 2 ", where "X" represents the halogen symbol.

43. Noble gas - Any member of the gaseous Group VIII elements that has an octet in their outermost sublevels. They are extremely stable ("satisfied") and therefore do not willingly react with other elements. Also called "inert gases" While originally thought to be totally un-reactive, compounds have been formed with Xenon, Krypton, and Radon.

44. Although relatively un-reactive, many uses exist: He - fills weather balloons He, Ne - mixed with O 2 for use in artificial atmospheres like those required for deep sea diving. Ar, Kr, Xe - used to produce inert atmospheres for flashbulbs and aluminum welding (as well as MIG & TIG welding).