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Understanding Electron Configuration

Essential Question: How are electrons organized for individual atoms?

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PRINCIPAL ENERGY LEVELSThe electrons in an atom are located at

specified distances from the nucleus and have different amounts of energy. Only seven (7) main --principal energy levels are necessary to account for the electrons of the known elements.

Connection to what you know: Seven periods----seven rings ---- Seven principal energy levels

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Energy Sublevels and Blocks on the periodic table

Principal energy levels can be divided into sublevels. There are 4 identified sublevels: s, p, d, and f. This is how we separate the blocks on the periodic table.

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OrbitalsA sublevel can further be divided into

orbitals, a region of space where an electron is likely to be found. Thus there are s orbitals, p orbitals, d orbitals, and f orbitals.

Each orbital can hold a maximum of 2 electrons

Sublevels Orbitals Electrons Possible

s 1 2

p 3 6

d 5 10

f 7 14

Each block contains a number of columns equal to the number of electrons that can occupy that subshell

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Now we can write the electron configuration notation (ECN) for any given atom

What is electron configuration?It is also the most stable arrangement of electrons around the nucleus of an atomWrite the ECN for Oxygen (atomic # 8, therefore 8 electrons)1s2 2s2 2p4 What does it mean?

2p4

Principal energy level

Sublevel

# of Electrons in that sublevel

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How does it relate to what you learned?Oxygen: Atomic # 88 electronsIts on the 2nd row so it has 2 orbitals

8p+

8n0

What you just learned:

1s2 2s2 2p4

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Examples ECN for Silicon

How many electrons? 14

Use the Aufbau Diagram or the location of the blocks to guide you.

Fill in your electrons. You must fill an orbital in a lower energy level prior to going to the next. Don’t skip around. Look at the chart that indicates the # of electrons per orbital

s = 2 e- p = 6 e-

1s2 2s2 2p6 3s2 3p2

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Practice: Use the back of your electron configuration information sheet

Electron Configuration Notation (ECN)

1. Sulfur:

2. Potassium:

Orbital Notation (ON)

3. Sulfur

4. Potassium

Noble Gas Notation (NGN)

5. Sulfur

6. Potassium

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Orbital Notation (ON)

Simply use lines and arrows instead of superscript numbers. Ex: Silicon

1s2 2s2 2p6 3s2 3p2

Keep in mind how many orbitals are in each of the sublevels listed. Use the chart on your info sheet.

s has one and p has three.

___ ___ ___ ___ ___ ___ ___ ___ ___

1s 2s 2p 3s 3p

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Noble Gas Notation (NGN)Short the configuration by using

the noble gas that comes right before the element.

Example: Silicon 1s2 2s2 2p6 3s2 3p2

The noble gas that comes right before this element (silicon) is neon (element #10).Remove the first ten electrons and replace them with the symbol for neon in brackets.[Ne] 3s2 3p2

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Rules to rememberThe Aufbau Principle This principle simply states that we can build up an

electronic configuration one electron at a time by putting each electron in the lowest energy orbital available.

The Pauli Exclusion Principle This principle says that an orbital is filled when it

contains 2 electrons. After that, you have to put the electrons in a different orbital.

Hund's Rule Within a subshell, the electrons will occupy the

orbitals singly first, and will only pair up when there are no longer any empty orbitals available in that subshell.