1. Electronic Structure 2. Electron Configuration 3. Core Notation 4. EC Relationship to Periodic Table 5. Electron Configuration of Ions

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1 Pre-AP Chemistry 11 Atomic Theory II Name: Date: Block: 1. Electronic Structure 2. Electron Configuration 3. Core Notation 4. EC Relationship to Periodic Table 5. Electron Configuration of Ions Electronic Structure What you should already know BOHR DIAGRAMS: Example: Calcium First shell has 2 electrons Second, third shell has 8 electrons Energy level A specific amount of which an in an atom can possess Bohr s Postulate #1 The hydrogen atom had only certain allowed or stationary states. The lowest (smallest) orbit was called the and designated n = 1. The larger orbits were called and designated as n = 2, n = 3, n = 4, etc. Bohr s Postulate #2 As long as the electron moved within the same energy level, the electron did not radiate or absorb energy Bohr s Postulate #3 The electron could only move from one allowed energy level to another if it or an amount of energy equal to the energy different between the two energy level.

subshell = orbital = can hold a maximum of electrons Ø Ex: 1s subshell looks like this: p subshell = orbitals = can hold a maximum of electrons Ø Ex: 2p subshell looks like this: d subshell =

2 Expanding Bohr s Theory Each energy level is split up into subshells and orbitals. Atomic Orbitals SHELL (science hallway) à SUBSHELL (room 212) à ORBITAL (row in the classroom) Each orbital can hold electrons We used to draw electrons as dots but now we will draw them as arrows: s subshell = orbital = can hold a maximum of electrons Ø Ex: 1s subshell looks like this: p subshell = orbitals = can hold a maximum of electrons Ø Ex: 2p subshell looks like this: d subshell = orbitals = can hold a maximum of electrons Ø Ex: 3d subshell looks like this: f subshell = orbitals = can hold a maximum of electrons Ø Ex: 4f subshell looks like this: In the Bohr model, the shells increase in numerical order = too simplistic! Orbitals increase in energy but not numerically Ø Electrons fill orbitals from the lowest energy Ø Can you read the diagram on the right? o Follow the arrows 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p How can we remember this order? Don t worry! It has to do with the way the Periodic Table is organized!!! Stay tuned

Electron Configuration & Orbital Diagrams Shows where the electrons are located within the orbitals There are three rules that we must remember: Rule #1:

Rule #2: Pauli Exclusion Principle Each orbital can hold a maximum of electrons.

4 Electron Configuration & Orbital Diagrams Shows where the electrons are located within the orbitals There are three rules that we must remember: Rule #1: Aufbau Principle Means in German When filling orbitals the energy orbitals available are always filled first. Rule #2: Pauli Exclusion Principle Each orbital can hold a maximum of electrons. Rule #3: Hund s Rule When orbitals of energy are being filled, electrons are most stable when orbital is -occupied before any orbital is -occupied. Let s practice! Element Number of electrons Lithium 3 Full Electron Configuration Orbital Diagram Beryllium 4 Boron Carbon Nitrogen Fluorine

5 Element Neon Number of electrons Full Electron Configuration Orbital Diagram Calcium Copper Strontium Xenon

6 Core Notation Sometimes we need a shortcut to write the electron configuration. We use NOBLE GASES to electron configuration to write out CORE NOTATION. Example: Magnesium Ø Full Electron configuration: 1s 2 2s 2 2p 6 3s 2 Ø Core notation: Practice: 1. Co 2. Rh 3. Ir 4. K 5. Rb 6. Cs 7. Cl 8. Br 9. I 10. N 11. P 12. As 13. Do you notice any patterns?

7 Electron Configuration Relationship to Periodic Table Electron Configuration of Ions Negative Ions: Example: Positive Ions: Two Rules: Write the core notation for the atom, then remove electrons in the order: Example: Write the electron configuration of the following ions, using core notation: 1. H - 2. Sr Br - 4. N 3+

8 5. Ti N 2-7. Mn Ge Fe Ge Ru Sb 3+ Use the periodic table to complete the following table: Atom or Ion Electron Configuration Core Notation Ge Zn 2+ Sr Br - Sn In 3+ Use the periodic table to identify the neutral atoms having the following electron configurations: Electron Configuration Element Name [Ne] 3s 2 [Ar] 4s 2 3d 5

9 [Kr] 5s 2 4d 10 5p 3 [Xe] 6s 2 4f 7 Consider the following six ions: N 3- O 2- F - Na + Mg 2+ Al 3+ a) How many electrons are present in each ion? b) Write a single electron configuration representing all of the ions. c) Which neutral atom posses this electron configuration? Complete the following table for some elements in two families of the periodic table: Alkali metals Core Notation # Outer Electrons Halogens Core Notation # Outer Electrons Lithium Fluorine Sodium Potassium Rubidium Chlorine Bromine Iodine a) Consider the number of outer electrons present and suggest a reason why elements belonging to the same chemical family demonstrate similar chemical behavior. b) What change occurs in the atoms as we move down each chemical family?

Electron Configurations

Section 3 Electron Configurations Key Terms electron configuration Pauli exclusion principle noble gas Aufbau principle Hund s rule noble-gas configuration Main Ideas Electrons fill in the lowest-energy