March 08, 2010
Electron Configurations Resonant Frequency Reminders: All atoms and molecules are in motion. From the Bohr model (1913) we know there are 7 principal quantum levels of energies around the nucleus. How close are we now for 8?? (From Schrodinger (1926) credit is given for the Wave Model and the beginning of being able to describe where electrons may be found. Electrons do not go in a circular pathway around the nucleus of an atom.
March 08, 2010
The main goal of this unit is to identify by an electron configuration an area that we would expect to predict/find the electrons of any specific atom. Along with this idea, the properties of atoms and how they change is based on electrons, students will understand why the Periodic Table "looks" and has such a meaningful shape and pattern. The 7 principle quantum energy levels around the nucleus represent the average energy of the electrons in that energy level. These principle energy levels are subdivided into s, p, d, f, subshells. s = sharp, p = principal, d = diffuse, f = fundamental Each subshell is divided into a specific number of orbitals. s p d f
subshell has subshell has subshell has subshell has
1 3 5 7
orbital orbitals orbitals oribitals
Each orbital can have up to 2 electrons. Each orbital has first one electron that is going in the same direction as every first electron in any other orbital. After the first electron is placed in each orbital of the subshell than the second electron can be added and is always going in the opposite direction of the first electron.
March 08, 2010
There are specific rules that determine how we fill the principle quantum levels with electrons. We will be learning some general rules and ways to predict, however remember that there are exceptions. First:
By the Aufbau principle we understand that for every proton in the nucleus there is an electron in the principle quantum level.
Second: By Hund's rule we know electrons fill to the lowest energy level. There are several thoughts to be considered here and these thoughts will be discussed later. Third:
By the Pauli Exclusion Principle every electron has a specific electron configuration. In other words each electron has a signature electron and energy levels. The four components will be given in class discussion.
Fourth:
Even with the designations above, since electrons are cruising at the speed 8 of light, 3.00 x 10 m/s, there is no way of knowing exactly where an electron will be found at any given time. We know what energy level (shell), what subshell, what orbital and which direction within the orbital but that is all. We call this the Heisenberg Uncertainty Principle. Based on all of this there is a degree of confusion of where the electron is found so often referred to as the "electron cloud".
March 08, 2010
Energy Levels First Principle Quantum Level Second Principle Quantum Level Third Principle Quantum Level Fourth Principle Quantum Level Fifth Principle Quantum Level Sixth Principle Quantum Level Seventh Principle Quantum Level
Subshells (n= 1) (n=2) (n=3) (n=4) (n=5) (n=6) (n=7)
1s 2s 3s 4s 5s 6s 7s
2p 3p 4p 5p 6p 7p
3d 4d 5d 6d 7d
4f 5f 6f 7f
(5g?) (6g?)
March 08, 2010
March 08, 2010
Reminder: Electron configurations are for atoms, not necessarily for elements or compounds. Write electron configuration for the following: H Li
Be
B
O
March 08, 2010
Write electron configuration for the following: Al Ca Co
As
I
W
March 08, 2010
Quiz: 1. Write the diagram to show the principle quantum levels, subshells, and the diagonal lines that show the order in which the subshells fill. 2.Write the electron configuration for Antimony. 3. By what principle did you use to find: a. the number of electrons?
__________________
b. which energy level and what order to fill?__________________ 4. List the 4 components of the Pauli Exclusion Principle.
March 08, 2010
Quiz: 1.Write the electron configuration for Gallium. 2. By what principle did you use to find: a. the number of electrons?
__________________
b. which energy level and what order to fill?__________________
March 08, 2010
Orbital Notation Shows with a picture of orbitals and how electrons fill by Hund's Rule H Li
Be
B
O
March 08, 2010
Draw Orbital Notations for the Following: Al Ca Co
As
I
Au
March 08, 2010
Quiz 1. Write the principle quantum levels, energy levels and lines that show the order in which the energy levels fill. 2. Write the electron configuration for Tellurium. 3. Write the orbital notation for Molybdenum. 4. What 4 components are necessary as detailed in the Pauli Exclusion Principle? 5. We learned one exception to the diagram in #1 was Lanthanum, what is the second exception on our Periodic Table? Write the inert gas configuration for Barium and Bismuth. Write the electron dot notation for Germanium and Iron. What is the Heisenberg Principle? What is Hund's Rule?
March 08, 2010
Quiz 1. Write the principle quantum levels, energy levels and lines that show the order in which the energy levels fill. 2. Write the electron configuration for Tellurium. 3. Write the orbital notation for Molybdenum. 4. What 4 components are necessary as detailed in the Pauli Exclusion Principle? 5. We learned one exception to the diagram in #1 was Lanthanum, what is the second exception on our Periodic Table? Write the inert gas configuration for Barium and Bismuth. Write the electron dot notation for Germanium and Iron. What is the Heisenberg Principle? What is Hund's Rule?
March 08, 2010
Write the electron configuration for Barium and Bismuth. Write the orbital notation for Germanium and Iron. What is the Heisenberg Principle? What is Hund's Rule?
March 08, 2010
Inert Gas Configuration. (Noble Gas Configuration) This is a short cut version to show the valence electrons of any element. Do not assume the version given on your Periodic Table is always of the correct form. The directions for doing an Inert Gas Configuration is to go back to the inert gas that comes before the atom being considered. Write the inert gas symbol in square brackets then complete the electron configuration. Example:
Se
=
[Ar] 4s2 3d10 4p4
Write the Inert Gas Configuration for: Ag
Ar
Ta
March 08, 2010
When atoms have energy presented to them, the atoms may take, give or share electrons. When atoms become ions, the ion they become is an attempt to have an outer shell of electrons the same as a noble gas (8 electrons). An atom that loses electrons will lose the outer shell electrons first. After the outer shell electrons are lost then electrons leave from the highest energy level. Write the electron configuration for the following: Fe Fe+2
Fe+3
Fe+6
March 08, 2010
Quiz: 1. Write the electron configuration for: a. Phosphorus b. Zirconium ion c. Cadmium 2. Write the inert gas notation for: a. Tellurium b. Barium 3. Write the orbital notation for: a. Indium b. Silicon 4. What are the 4 components of the Pauli Exclusion Principle? 5. Write the electron dot notation for
Ga
Br
Bi
March 08, 2010
March 08, 2010
(H) Quiz 1. Write the electron configuration for
Germanium and Terbium.
2. Write the inert gas configuration for 3. Write the orbital notation for
Krypton and
Cobalt
and
Polonium.
Titanium.
4. By what principle do we need 4 components to represent an electron? 5. What are the 4 components that are necessary to identify any electron? 6. How many electrons are in the outer shell of Lead? 7. Write the electron dot notation for
Lead
Zinc
and
Sulfur.
8. Is a 3f energy level higher or lower in energy than a 3d? 9. Why is lanthanum an exceptional element? 10. Can you explain using electron configurations and the electron dot notation why oxygen is found as a molecule not an atom?
March 08, 2010
Quiz/Warmup 1. Write the electron configuration for Germanium. 2. Write the inert gas configuration for Krypton. 3. Write the orbital notation for Cobalt. 4. By what principle do we need 4 components to represent an electron? 5. What can you say is the same about all halogens and electron configurations?
March 08, 2010
Quiz/Warmup 1. Write the electron configuration for Germanium. 2. Write the inert gas configuration for Krypton. 3. Write the orbital notation for Cobalt.
4. By what principle do we need 4 components to represent an electron? 5. What can you say is the same about all halogens and electron configurations?
March 08, 2010
Quiz
March 08, 2010
Electron Dot Notation Once you know the structure and the order of which electron fill energy levels, then most often the electron dot notation is used to show the valence electrons. Remember that valence electrons are also called outer shell electrons. Isn't the Periodic Table built on the idea of electrons and energy levels? By looking at an electron configuration or by knowing the "system" of the Periodic Table, (including the exceptions), you can tell/predict how many electrons are in the outer shell of any element. The format for an electron dot notation is: Let the symbol X be representative of any element then put dots representing outer shell electrons around X in the order shown
X Note: You use dots to represent the electrons not numbers. If no electron, leave the space empty.
March 08, 2010
Lets consider Arsenic. Arsenic has 6 electron in the outer shell. ( You should be able to verify by drawing/writing an electron configuration.) So then the electron dot notation for Arsenic would be
As
At first this may seem difficult but keep neat and in order. Placing a dot out of order or in an order that is questionable will be marked wrong. (Dots are to be just to the sides of bisector lines.) Practice: Br
Si
Ti
K
Rn
Al
Te
March 08, 2010
Atomic Size Even though you can find the atomic size on the back side of our Periodic Table, I will remind that our goal is to see atomic trends and patterns. Most often you do not have the great Periodic Table you have for use in class available and you will need to use the patterns you learn to answer questions. These type of questions come up in chemistry SAT tests or in general tests as well. Atomic Size follows patterns based on the electrons and energy levels that we have talked about this unit. Atom size is determined by both the nucleus and the electrons that are going around the nucleus. We can often be successful in determining relative size by considering 3 factors. Shells Protons Electrons
March 08, 2010
Remember that the principle quantum level is often referred to as the shell. So the shell count would be the same as the period of the Periodic Table that any element is found. Remember that an ion loses the outer shell electrons first and most often goes to a lower period number especially when a metal. Nonmetals often stay in the same period when they become ions. Comparing an atom of Manganese being in the 4th principle quantum level would be larger than an atom of Phosphorus which has 3 principle quantum levels. Bismuth would be smaller than Francium. (6 shells vs. 7 shells for Francium) Always consider shells first. Just like the examples given this is the quickest way to compare sizes of atoms in different rows of the Periodic Table.
March 08, 2010
If shells will not determine which atoms is larger or smaller then consider the number of protons. This would be the case if the elements being compared were in the same row of the Periodic Table. Consider Potassium and Iron. Which is smaller? Potassium has 4 shells, 19 protons and 19 electrons. Iron has 4 shells, 26 protons and 26 electrons. Same shells so consider the protons. Protons are positively charged and are of a larger mass than negatively charged electrons. Based on the electrostatic attraction between positive and negative charges of these particles, is the nucleus going to move to the electrons or is the electrons going to move to the nucleus? Answer
electrons are pulled in towards the nucleus making the size of the atom smaller.
From this we would understand that the more protons within a shell will make an atom smaller in size. Thus Iron is smaller than Potassium due to the same number of shells, and more protons. Could be said from the opposite perspective: Potassium is larger due to same shells and less protons.
March 08, 2010
If shell and protons do not distinguish, then compare by electrons. Example: Which is bigger Ni+3 or Ni+2 ? +3 +2 Ni loses 3 electrons and Ni loses 2 electrons, which means that both have the same number of shells (3) since you lose the outer shell electrons first. Nickel has 2 electrons in the outer shell and loses these two electrons first so loses 1 shell count. Ni+3 or Ni+2 both have the same number of protons which identify Nickel. So the number of protons does not aid in determining size. Since the first two do not distinguish go by the number of electrons. The more electrons the bigger the ion size. Ni+3 has 25 electrons and Ni+2 has 26 electrons so Ni +2 is larger.
March 08, 2010
Practice: Which is larger? Co or Ga
Explain why
Si
Explain why
I
or Ca or
Ag
Explain why
C-4 or C+4
Explain why
Rank the following from smallest (1) to largest (however many are compared) Sn ___
Sr ____
Sb ____
S ___
Ga ___
Cr ___
Sc ____
Fe+3 ____
Ti+2 ____
Rb ___
Al ____
March 08, 2010
Quiz: (1/2 sheet) Rank the following: W
Ag
___
___
S-2 ____
F
K
____
____
Nb
U
____ ____
No ____
S+6 ____
shells protons electrons
If the diagonal rule applies, then use the same ranking to show approximately the same size.
March 08, 2010
Quiz: (1/2 sheet) Rank the following: W
Ag
___
___
S-2 ____
F
K
____
____
Nb
U
____ ____
No ____
S+6 ____
shells protons electrons
If the diagonal rule applies, then use the same ranking to show approximately the same size.
March 08, 2010
