Electron Configuration Chapter 3 Section 3.2

Things we know… Electrons are negatively charged. Electrons are very small 1/2000 that of a proton or neutron X grams Electrons determine the chemical behavior of the atom.

According to Modern Atomic Theory: Electrons travel around the nucleus billions of times per second. Not in perfect orbits like seen here in the Bohr Model, but rather in complex patterns in a space called the “ electron cloud.” The exact location of an electron is never known!!

n = energy level How many energy levels does Li have? How many energy levels does Sr have? Determining Energy Level

Energy Levels = Periods A row on the periodic table is called a period. What period is Ca in? Al is in the third period, how many energy levels does it have? Overhead notes here

Energy levels can hold a certain number of electrons 2 8 8

Energy levels have sublevels called “orbitals.” S Orbitals P Orbitals We will work with two types:

S Orbitals can hold 2 electrons P Orbitals can hold 6 electrons

Add up electrons orbitals hold and you know how many electrons the level can hold

4Larger energy levels have more orbitals. 4Besides “s” and “p” orbitals, there are also “d” and “f” orbitals. 4Orbitals have different unusual shapes.

S Orbitals are sphere-shaped.

P Orbitals are dumbbell-shaped.

d & f Orbitals have wild shapes.

A Copper atom simulation!

Energy levels have sublevels called orbitals Energy levels have 1 to 4 different orbitals. The orbitals are called S P D F The periodic table reflects the arrangement.

What are Orbitals? The places electrons probably are- They look like Spheres Dumbbells Donut things…Ab roller

Energy Levels have 1 – 4 orbitals Period 1 has 1 orbital, what is it? Period 2 has 2 orbitals, what are they? How many orbitals does period 3 have?

A. General Rules Pauli Exclusion Principle Each orbital can hold TWO electrons with opposite spins. We note this with two arrows going in the opposite directions. You can use any symbol you choose but use something.

A. General Rules Aufbau Principle Electrons fill the lowest energy orbitals first. “Lazy Tenant Rule” You see the ground floor is easy but climbing the stairs is hard work! Ground Floor

RIGHT WRONG A. General Rules Hund’s Rule Within a sublevel, place one e - per orbital before pairing them. “Empty Bus Seat Rule”

O 8e - Orbital Diagram zElectron Configuration 1s 2 2s 2 2p 4 B. Notation 1s 2s 2p

zShorthand Configuration S 16e - Valence Electrons Core Electrons S16e - [Ne] 3s 2 3p 4 1s 2 2s 2 2p 6 3s 2 3p 4 B. Notation Longhand Configuration

s-block1st Period 1s 1 1st column of s-block C. Periodic Patterns Example - Hydrogen

C. Periodic Patterns Shorthand Configuration Core e - : Go up one row and over to the Noble Gas. Valence e - : On the next row, fill in the # of e - in each sublevel.

Writing electron configuration S-orbitals always fill first. Each s-orbital can hold 2 electrons.

Lets Try Another! P orbitals can hold up to 6 electrons P orbitals only fill when the s orbital before it has filled Nitrogen has 7 electrons 1s 2 2s 2 2p 3

Writing Electron Configuration Nitrogen has seven electrons 1s 2 2s 2 2p 3 Neon has ten electrons How would Ne be written? 1s 2 2s 2 2p 6

Why do we need this stuff??? To determine the valance electrons Electrons in the outermost energy level Valance electrons help determine the chemical activity of the element.(Its attitude) How many valance electrons does carbon have? 1s 2 2s 2 2p 2 How many valance electrons does Beryllium have? 1s 2 2s 2

Those Crazy Electrons!