Modern Model of the Atom

Quantum Mechanical Model Does not describe the movement of the electrons, only where they are at any point in time. Orbital – a region in which an electron will have the greatest probability of being found. (Any orbital can hold two electrons.) Golf ball in water on string.

Quantum Numbers Set of 4 numbers describes everything you need to know to find an electron. (Tells its address.)

Principle quantum number (n) Tells the distance from the nucleus The main energy level Numbers 1-7 Corresponds to rows on the periodic table If n (principle) = 1, then there can only be an s orbital. If n = 2, there can be s and p orbitals. If n = 3 there can be an s, p and d.

Number of Electrons The total number of electrons that CAN be held in a principle energy level is 2n2 Example: The 5th principle energy level can hold 2(52) = 50 e-

Orbital Quantum Number s – 1 in a principle energy level p – 3 in a principle energy level Each of the p’s pictured is an orbital, each holds 2 electrons, so together, the p orbitals hold 6 electrons.

Orbital Shapes Continued d – 5 in a principle energy level The f orbitals are too complicated to draw. 4 of this type 1 of this type f – 7 in a principle energy level

Finding Orbital Quantum #s on the Periodic Table P Block S Block D Block F Block

Magnetic Quantum Number Tells the position in space. s – 1 position (2 e- total) p– 3 positions (6 e- total) d – 5 positions (10 e- total) f – 7 positions (14 e- total)

Spin Quantum Number Tells the direction of spin. Pauli Exclusion Principle: No two electrons can have the same of Quantum Numbers

Orbital Notations and Electron Configurations

Filling Order The “s” shape starts in principle energy level 1. p in 2 d in 3 f in 4

Filling Order Continued The “d” shapes are 1 row lower than they are supposed to be. The “f” shapes are 2 rows lower.

Finding Orbital Quantum #s on the Periodic Table P Block S Block D Block F Block

Orbital Notation Shows all four quantum numbers for every electron in the atom. A box or line is one orbital. An arrow is one electron.

Orbital Notation for Silicon Silicon has 14 electrons, so you will draw 14 arrows. 1s 2s 2p 3s 3p

More Examples: Magnesium Copper Chlorine 1s 2s 2p 3s 1s 2s 2p 3s 3p 4s 3d 1s 2s 2p 3s 3p Chlorine

Electron Configurations Shorthand versions of orbital notations. Does not indicate the magnetic or spin quantum numbers. Tells the total number of electrons in each SET of orbitals.

Writing an Electron Configuration Write the electron configuration for Neon. 1s22s22p6 Principle Quantum Number Subshell Total Number of Electrons Go over each part. Note that the number of electrons doesn’t tell you the spin or which orbital it is in. Discuss the fact that each orbital fills one e before any one gets a second.

Your Turn Write the electron configuration for Potassium. Write the electron configuration for Copper Write the electron configuration for Bromine

Answers 1s22s22p63s23p64s1 1s22s22p63s23p64s23d9 Potassium 1s22s22p63s23p64s1 Copper 1s22s22p63s23p64s23d9 Bromine 1s22s22p63s23p64s23d104p5

Excited State Electrons You can also draw and recognize elements with electrons in the excited state from an electron configuration. For example: What element is shown? 1s22s22p63s13p1

What did you answer? This is NOT Aluminum (Al), this is Magnesium (Mg) in the excited state!! Why? Look at the 3s sublevel… 1s22s22p63s13p1