Knowing the position of electrons helps us with many topics: Why chemical reactions occur Why some atoms are more stable than others Why some elements react with only certain atoms Goal for this topic: We want to know how many electrons an atom has, and where they’re located.
“Electron Cloud” - Energy Levels ( 1 – 7) - Sublevels (S,P,D,F – Shapes) - Orbitals (Specific Pathways – X/Y/Z axis)
© 1998 by Harcourt Brace & Company s p d (n-1) f (n-2)
Nucleus - S Sublevel – Think Sphere - P Sublevel – Figure 8 S Sublevel P Sublevel- X Axis P Sublevel- Y Axis P Sublevel- Z Axis
Orbital Diagrams are Visual illustrations that show the order that electrons will follow as they fill in the electron cloud. We start from the bottom and work your way up. That symbolizes starting on the first energy level and work outward.
When filling in an orbital diagram, it’s important to follow three rules. You need to know these by name and what each specifically says, so get ready to write them!
Aufbau Principle Electrons must fill the lowest sublevel available. (Letters - S,P,D,F) You cannot skip any sublevels. It’s like the Alphabet!
Pauli Exclusion Principle Each orbital (each box on the diagram) can hold only TWO electrons, and the electrons have opposite spins.
RIGHT WRONG Hund’s Rule Within a sublevel, place one electron in each orbital with the same spin before pairing them with a second electron. - “Empty Seat Rule”
You are drawing arrows, and they represent electrons. (Neon has 10 electrons so you will need to draw 10 arrows.) Divided up into different sublevels containing a specific number of orbitals. KNOW THIS INFO! - The S sublevel has only 1 orbital= total of 2 e- - The P sublevel has 3 orbitals = total of 6 e- - The D sublevel has 5 orbitals = total of 10 e- - The F sublevel has 7 orbitals = total of 14 e-
Fill in the orbital diagram for Magnesium
An atom’s electron configuration… Describes the location of electrons within the atom Identifies the shape of the electron clouds - regions where the electrons are held. Uses numbers and letters to describe electrons’ location and which electron cloud it is part of.
1s 2 The “1” tells you how far from the nucleus the electrons can go. In this case, its in the 1 st energy level, which is the closest level to the nucleus. The “s” tells you the electron’s cloud shape. In this case it’s a spherically shaped cloud. It is called the s sublevel. Sublevel = Shape The “2” simply tells you how many electrons are in this cloud. In this case 2 electrons are creating the cloud. Note: Every orbital can only hold 2 electrons. They must have opposite spins.
O 8e - Orbital Diagram zElectron Configuration 1s 2 2s 2 2p 4 1s 2s 2p
Shorthand Configuration This is a shorter way to do e - configurations Steps… 1) Write the symbol of the element you’re doing 2) Find the noble gas (group 8) that comes before the element you are doing. 3) To begin, put that noble gas in [brackets] 4) Starting with that noble gas, finish the electron configuration
zShorthand Configuration S 16e - Valence Electrons Core Electrons S16e - [Ne] 3s 2 3p 4 1s 2 2s 2 2p 6 3s 2 3p 4 Longhand Configuration
[Ar]4s 2 3d 10 4p 2 Example - Germanium
LiNMg C
This will help It is a way to remember the order in which electrons fill their orbitals. When you reach the far Left side, you reach a “wall” and must go back to The right hand side.