Understanding Electron Configuration

1. Understanding Electron Configuration Essential Question: How are electrons organized for individual atoms?

2. PRINCIPAL ENERGY LEVELS • The 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

3. 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.

4. Orbitals Each block contains a number of columns equal to the number of electrons that can occupy that subshell • A 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

5. 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 atom Write the ECN for Oxygen(atomic # 8, therefore 8 electrons) • 1s2 2s2 2p4 What does it mean? 2p4 # of Electrons in that sublevel Principal energy level Sublevel

6. How does it relate to what you learned? Oxygen: Atomic # 8 8 electrons Its on the 2nd row so it has 2 orbitals 8p+ 8n0 • What you just learned: 1s2 2s2 2p4

7. 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

8. 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

9. Orbital Notation (ON) Simply use lines and arrows instead of superscript numbers. Ex: Silicon 1s2 2s2 2p6 3s23p2 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

10. 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

11. Rules to remember • The 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.