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Chapter 4-Arrangement of Electrons in Atoms Carbon:1s22s22p2 + Bell Ringer • Locate the worksheet entitled: The History of the electron as we know it(glue into to notebook). – There are extras on the table if you need one – Fill in as much of it as you can. – You should be able to answer several of them – This should prepare you to begin today’s lesson on the Quantum Model • Grab a sheet that has the squares on it as well (Glue into notebook). Relationship between an Atom and Energy • Ground State: The lowest energy state of an atom. • Excited State: The state in which an atom has absorbed energy. The electrons are further away from the nucleus. • Quantum: The amount of energy needed to move an electron from one energy level to the next. (From Ground state to an Excited state) • Photon: A particle of light that is carrying a quantum of energy. • Absorb- When an atom receives energy then it Absorbs energy. Bohr Model • Emit- When an atom gives off energy then it is emitting energy. • Niels Bohr -developed a model of a hydrogen atom that showed the electron circling the nucleus in a fixed path. – He determined that each energy level had a particular amount of electrons that could occupy each level. (fill in worksheet) • 2 things wrong with Bohrs Model: – It only worked for Hydrogen • why? – It didn’t explain the atoms bonding ability or chemical behavior (video) The Quantum Model • Heisenberg Uncertainty Principle-It is impossible to know both the position and velocity of an electron at the same time. – Mice and Cockroaches!! • Quantum Model-Model that shows the location of all electrons in an atom • Orbitals- three dimensional region around the nucleus that indicates the probable location of an electron. – 90% of the time Quantum Numbers • Quantum Numbers- 4 numbers used to tell us where an electron is located in an atom 1. Principal Quantum Number (n) 2. Angular Momentum Quantum Number ( l ) 3. Magnetic Quantum Number 4. Spin Quantum Number Quantum Numbers • Pauli Exclusion Principle: no two electrons in the same atom can have the same set of quantum #s. 1-Principal Quantum # • Tells us which energy level an electron is in • Symbolized by n • Can have a value of 1,2,3,4,5,6,or 7 – Example n=3 means the electron is in the 3rd energy level. 2-Angular Momentum Quantum # • Gives the shape of the orbital the electrons are making • Symbolized by ( l ) • ( l ) can have a value of s, p, d, or f #2-Angular Momentum s Orbital • • • • • s can have only ONE part spherical or round shape (like a ball) Can hold 2 electrons total Lowest in energy Periodic table Groups 1-2 SubOrbitals • Some of the Orbital shapes have parts • Each part can hold only TWO electrons each. #2-Angular Momentum p Orbital • p orbital can have THREE orientations -orientated on the x axis -orientated on the y axis -orientated on the z axis • dumbbell shaped • Each dumbell can hold 2 e• 3 different orientations account for the total of 6 electrons in the p Orbital ( 3 x 2=6) • Periodic table Groups 13-18 • Second lowest in energy #2-Angular Momentum d Orbital • 5 different orientations • Each d shape can hold 2 e• 5 different orientations account for the 10 possible electrons (5x2=10) • d sublevels are described as being lobed • Periodic table groups 3-12 • Third in energy #2-Angular Momentum f Orbital • f sublevels can have 7 orientations • Each shape can hold 2 e• resulting in a maximum of 14 electrons in the f orbital ( 7 x 2=14) • Shape not important • Periodic table groups: Lanthanides and Actinides (the two rows at the bottom) • Highest in energy #2-Angular Momentum s Orbital • s sublevel can have only ONE orientation or part • spherical or round shape (like a ball) • Can hold 2 electrons total • Periodic table Groups 1-2 • Lowest in energy 3-Magnetic Quantum # • Tells us which plane or axis the orbital is in 4-Spin Quantum # • Tells us if the electron is spinning clockwise or counter-clockwise Electron Configurations • Shows the arrangement of electrons in atoms (address or blueprint) • In the neutral state each element has a different electron configuration, b/c every element has a different # of electrons. Aufbau principle • States that an electron occupies the lowest-energy sublevel that can receive it. • Electrons take the path of least resistance..Lazy Electrons - How to know where electrons fill? • Electrons always fill lowest energy level first (1,2,3,4,5,6,7) • Electrons fill lowest orbital in each energy level first (s,p,d,f) Representing Electron Configurations Four ways to show arrangement of electrons 1. Electron Configuration Notation(long) 2. Noble Gas Configuration(short cut) 3. Orbital Notation(arrows) 4. Electron Dot Notation(dots) 1-Electron Configuration Notation • Shows all electrons in atom • Gives – Energy Level – Shape of Orbital – Number of electrons in each orbital • Example: Hydrogen 1S1 # of electrons Orbital Type Main Energy Level How to write electron configurations • Always start with 1s • Continue to fill orbitals as needed • When you have to jump to the next energy level, ALWAYS start back filling in the s orbital. • Remember that all energy levels have an s orbital. Electron Configuration-period two elements • • • • • • • • • • H He Li Be B C N O F Ne 1s1 1s2 1s22s1 1s22s2 1s22s22p1 1s22s22p2 1s22s22p3 1s22s22p4 1s22s22p5 1s22s22p6 Electron Configurations-period three elements • • • • • • • • Na Mg Al Si P S Cl Ar 1s22s22p63s1 1s22s22p63s2 1s22s22p63s23p1 1s22s22p63s23p2 1s22s22p63s23p3 1s22s22p63s23p4 1s22s22p63s23p5 1s22s22p63s23p6 Fourth period elements • So far, electrons have filled in a predictable order. • This changes in the fourth period. • 4s will fill before 3d, because 4s has less energy than 3d. (electrons always take path that uses less energy) Fourth period elements • • • • • • • • • • • K Ca Sc Ti Zn Ga Ge As Se Br Kr 1s22s22p63s23p64s1 1s22s22p63s23p64s2 1s22s22p63s23p64s23d1 1s22s22p63s23p64s23d104p1 Exception to every rule • There are some exceptions to the Aufbau principal for elements 24 and 29 – Cr: 1s2 2s2 2p6 3s2 3p6 4s1 3d5 – Cu: 1s2 2s2 2p6 3s2 3p6 4s1 3d10 Elements of the fifth period • Rb • Sr 1s22s22p63s23p64s23d104p65s1 1s22s22p63s23p64s23d104p65s2 Write the electron configuration notation for the following: • 1. Boron (B) • 2. Magnesium (Mg) • 3. Argon (Ar) • 4. Calcium (Ca) • 5. Bromine (Br) Noble gas configurations -A short hand way of writing an electron configuration using noble gases. -First, determine what period the element is in. -Second, put the noble gas in the previous period in [ ]. The noble gas in [ ]accounts for its atomic # of electrons. Noble gas configurations • Compare the configuration of the noble gas Ne to all of the period 3 elements. All period 3 elements start off with Neon’s configuration • Ne 1s22s22p6 • Na 1s22s22p63s1 • Mg 1s22s22p63s2 • Al 1s22s22p63s23p1 • Si 1s22s22p63s23p2 • P 1s22s22p63s23p3 • S 1s22s22p63s23p4 • Cl 1s22s22p63s23p5 • Ar 1s22s22p63s23p6 Noble gas configurations • Third-start filling with the energy level that equals the period #. • Ex: write the noble gas configuration for sodium, Na – Na is in the 3rd period, so use the noble gas in the 2nd period, which is Ne – [Ne]3s1 Hund’s Rule • States that each part of an orbital should get 1 electron before any of the parts can have 2. • Don’t be stingy you have to share!!! Orbital Notation • Coincides with electron configuration notation. • Orbital notation is a diagram that shows Hund’s rule. Dot notation • Shows only valence shell (outer) electrons - - - • • • • • • • • Group 1 has 1 valence electron Group 2 has 2 valence electrons Group 13 has 3 valence electrons Group 14 has 4 valence electrons Group 15 has 5 valence electrons Group 16 has 6 valence electrons Group 17 has 7 valence electrons Group 18 has 8 valence electrons - Dot notation continued • First-write the symbol of the element • Second-determine the group of the element and decide # of outer electrons • Third- Place dots around the symbol to represent electrons in the outer shell Electron Arrangement Quiz • 1. 3. 5. Write the electron configuration for the following: K 2. Cl Mg 4. Ga F 6. Be • What element have the following configuration: 7. 1s22s22p63s23p64s23d6 8. 1s22s22p4 9. [Ar] 4s23d5 • Write the noble gas configuration for the following: 9. S 10. P 11. Cl 12. Zr Electron Arrangement Quiz • 1. 3. 5. Write the electron configuration for the following: Na 2. Cl Mg 4. Al Br 6. Li • What element have the following configuration: 7. 1s22s22p63s23p3 8. 1s22s2 • Write the noble gas configuration for the following: 9. Sr 10. Si 11. Cl 12.Y