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Quantum Mechanical Model Notes  Electrons DO NOT travel around the nucleus of an atom in orbits like planets around a sun.  Orbitals are 3-D areas around.

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Presentation on theme: "Quantum Mechanical Model Notes  Electrons DO NOT travel around the nucleus of an atom in orbits like planets around a sun.  Orbitals are 3-D areas around."— Presentation transcript:

1 Quantum Mechanical Model Notes  Electrons DO NOT travel around the nucleus of an atom in orbits like planets around a sun.  Orbitals are 3-D areas around the nucleus with a high probability of finding electrons.

2  The higher the density of dots indicates the higher (most) probable location(s) of electron(s).  Boundary line = 90% probability of finding electrons within the circular region.

3  Each electron in an electron cloud has a four-part quantum number. This is like a street address.  Principle Quantum #1 (n):  Indicates the relative size and energy of orbitals. It is designated with numbers, 1- 7).  Electrons are found at different distances away from the nucleus in different energy levels.

4  Electrons cannot exist between energy levels (they are like the rungs of a ladder).  Only a certain number of electrons may exist in a given energy level, but the number varies. It can be determined by a formula: Total number of electrons in level = 2 x (# of energy level ) 2 4

5  For Example:  Energy level 1 = 2 (1) 2 = 2  Energy level 2 = 2 (2) 2 = 8 Solve for the energy levels below using the equation (2 x (# of energy level) 2  Energy level 3 =  Energy level 4 =  Energy levels are broken up into sublevels: 5

6 Principle Quantum #2 (s; p; d; f; etc.): Are called energy sublevels and have specific orbital shapes. Table Team — what is the relationship between n and sublevels? 6

7  Prinicple Quantum Number 3:  Designates the orientation of orbitals in the electron cloud.  Principle Quantum Number 4:  Designates the ‘spin’ of an electron (either clock-wise or counter clock wise), allowing two electrons to occupy the same orbital.  Each electron has a unique set of four quantum numbers. 7

8  Principle Energy Level 1:  Only has one s sublevel (a spherical shape; see model).  A sphere has only one orientation in the space of the electron cloud.  Two electrons may fit in this sublevel—each one has an opposite spin.  Pauli exclusion principle —no more than two electrons may be found in the same orbital. 8

9 An ‘s’ Orbital 9

10  Principle Energy Level 2:  Has two energy sublevels: s and p.  There are 2 electrons in a ‘s’  There are 3 different p orbitals, each can hold 2 electrons for 6 total. (‘dumb-bell’ shape; three orientations in electron cloud space).  There can be a total of 8 electrons overall in energy level 2. 10

11 11 ‘p’ Orbitals

12  Principle Energy Level 3:  has 3 sublevels: s, p, and d.  Two electrons in the s orbital  Six total electrons in the three p orbitals.  There are 5 different d orbitals, and 2 electrons can fit in each— for a total of 10.  Total of 18 electrons for energy level 3. 12

13 d-orbital notes 13 The five ‘d’ Orbital Images

14  Principle Energy Level 4:  Has 4 sublevels: s, p, d, and f.  2 electrons in s  6 electrons in p  10 electrons in d  14 electrons in f (7 different orbitals for f)  A total of 32 electrons in this energy level. 14

15 Seven ‘f’ orbitals 15

16  The order that electrons fill up orbitals does not follow the logical order of all 1’s, then all 2’s, then all 3’s, etc. 16

17  The first rule states that each electron occupies the lowest energy level possible. This is called the Aufbau principle.  The second rule for filling orbitals is that only one electron will be put in each orbital of a sublevel until all of them are filled, and after that, they may be paired up until the sublevel is full. This is called Hund’s rule. 17

18  An easy way to remember this is to use the periodic table--it is arranged to show how these orbitals are filled. Stay tuned! 18


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