The Modern Atomic Theory: A Closer Look at the Electron

Blocks in The Periodic Table = s block = d block Row # = p block = f block 1 2 3 4 5 6 7

Where is the Electron? In the quantum mechanical model, the electrons are found outside the nucleus. To describe an electron’s location, we can includes Its Energy Level Its Sublevel Its Atomic Orbital

Principle Energy Levels The first horizontal row of the periodic table represents the first or (n=1) principle energy level. Represented by the letter, n n = 1  First Energy Level Each new row on the periodic table starts a new energy level. Each energy level has a different number of sublevels, a different number of orbitals, and a different number of electrons.

The Bohr Model

Higher Energy Level = Bigger Sublevel Sublevels Based on the number of elements in our Periodic Table, there are four sublevels. s, p, d, f Each sublevel has a unique shape. The size of the sublevel depends on the energy level. Higher Energy Level = Bigger Sublevel

s-Sublevel sphere

This is only one of the p-sublevel atomic orbitals. p-Sublevel dumb bell This is only one of the p-sublevel atomic orbitals.

Since there are 3 orbitals in the p-Sublevel:

d-Sublevel Don’t need to memorize these!

f- Sublevel Don’t need to memorize these!

Summary of the Sublevels Number of Atomic Orbitals Maximum Number of Electrons s 1 2 p 3 6 d 5 10 f 7 14

Atomic Orbitals All electrons are located in an atomic orbital or orbital. An atomic orbital represents the area in which there is a 90% chance of finding an electron. Each atomic orbital can hold two electrons. Inside these orbitals, electrons take random and unpredictable paths.

Processing Your Notes Question #1 1. Which sublevel has a dumbbell shape? s sublevel p sublevel d sublevel f sublevel The p-sublevel has a dumbbell shape, while the s-sublevel has a spherical shape.

Processing Your Notes Question #2 2. Which sublevels will have the same shape? 3s and 3p 3p and 4p 1s and 2p 4d and 3s The letter or sublevel determines the shape.

Processing Your Notes Question #3 3. Sodium is found on the third row or Period 3 of the periodic table. How many energy levels do the electrons of a sodium atom occupy? 1 3 11 23 3rd Row = 3 Energy Levels

Processing Your Notes Question #4 4. How many orbitals are found in a d-sublevel? 4 5 10 14 Be Careful! The d-sublevel has 5 orbitals and holds 10 electrons. You will want to memorize that table!

Processing Your Notes Question #5 5. How many electrons can be held in one atomic orbital? 2 6 10 14

Processing Your Notes Question #6 6. Which letter does not represent a current sublevel of an energy level? d f n p n represents the energy level not a sublevel.

Processing Your Notes Question #7 7. As scientists create new elements, we will need to add new sublevels to the four existing sublevels. In fact, the next sublevel will be called g. After looking at the trend in the number of orbitals for the current sublevels, how many orbitals would you predict would exist in a g-sublevel? 7 8 9 32 s =1 p = 3 d = 5 f = 7 g = 9

Putting It All Together 1 s 2 2 s & p 4 8 3 s, p, & d 9 18 4 s, p, d, & f 16 32

Electron Configurations Electron Configurations represent the location of the electrons in an atom or ion. 1s22s22p5 the number of electrons the energy level of the electron (n) the sublevel

Processing Your Notes Question #8 8. How many orbitals are in the fourth energy level? 4 8 16 32 For the fourth energy, you have s, p, d and f. s = 1 orbital p = 3 orbitals d = 5 orbitals f = 7 orbtials Add these up! 1 + 3 + 5 +7 = 16

Processing Your Notes Question #9 9. How many electrons are held in n=2? 2 4 8 16 n=2 means the second energy level. s = 2 electrons p = 6 electrons Add these up! 2 + 6 = 8 electrons

Processing Your Notes Question #10 10. Which of the following sublevels does not exist? 1s 2d 3p 4f On the first energy level, you only have 1s. On the second energy level, you only have 2s and 2p. On the third energy level, you only have 3s, 3p, and 3d. All four sublevels are on the fourth energy level.

Processing Your Notes Question #11 11. Which of the following would be an expression used to calculate the number of orbitals based on the energy level (n)? 2n n2 n + 6 2n2 n = 1 n2 = 1 n = 2 n2 = 4 n = 3 n2 = 9 n = 4 n2 = 16

Processing Your Notes Question #12 1s22s22p63s23p4 12. Which element is represented by this electron configuration? sodium sulfur argon selenium Add up the exponents! Since it is neutral, protons = electrons.

Processing Your Notes Question #13 1s22s22p63s23p4 13. What is the highest energy level in this electron configuration? 2 3 4 6 Energy level represented by the coefficient or the big number.

Processing Your Notes Question #14 1s22s22p63s23p4 14. How many electrons are found in the s-sublevel? 2 4 6 8 2 + 2 + 2 = 6

Processing Your Notes Question #15 1s22s22p63s23p64s23d104p1 15. Which sublevel has the most electrons? s p d f p = 13 electrons d = 10 electrons s = 8 electrons

Processing Your Notes Question #16 1s22s22p63s23p64s23d104p1 16. How many electrons are in the highest energy level? 1 2 3 13 The “coefficient” determines the energy, so 4s and 4p are both on the highest energy level.

Processing Your Notes Question #17 1s22s22p63s23p64s23d104p1 17. What element is represented by the electron configuration? titanium copper gallium germanium Add up the exponents! Since it is neutral, protons = electrons.

Rule #1: Pauli’s Exclusion Principle Each atomic orbital can hold two electrons. Sublevel # of Orbitals Max # of Electrons s 1 2 p 3 6 d 5 10 f 7 14

Rule #2: Aufbau Principle Electrons will fill the atomic orbital with the lowest energy first. 1s22s22p63s23p64s23d104p5 Lowest Energy  Highest Energy

Blocks in The Periodic Table = s block = d block Row # = p block = f block 1 2 3 4 5 6 7

Sample Electron Configurations Hydrogen  1s1 Beryllium  1s22s2 Fluorine  1s22s22p5 Chlorine  1s22s22p63s23p5 Potassium  1s22s22p63s23p64s1

Important Reminders Your row number tells you the energy level or coefficient for your configurations. Know your limits for each sublevel! You have to use your periodic table be sure that you are following the Aufbau Principle. 1s  2s  2p  3s  3p  3d 1s  2s  2p  3s  3p  4s X

Electron Configurations (Containing the d-Sublevel) The energy level of d-sublevel will ALWAYS be one less than the row or period number.

Blocks in The Periodic Table = s block = d block Row # = p block = f block 1 2 row # -1 3 4 5 6 7

Sample Electron Configurations Titanium Iron Bromine Tellurium Silver 1s22s22p63s23p64s23d2 1s22s22p63s23p64s23d6 1s22s22p63s23p64s23d104p5 1s22s22p63s23p64s23d104p65s24d105p4 1s22s22p63s23p64s23d104p65s24d9

Where does the f-block “fit in”? The f-block is considered to be part of periods 6 and 7.

Electron Configurations (Containing the f-Sublevel) The energy level of f-sublevel will ALWAYS be two less than the row number.

Blocks in The Periodic Table = s block = d block Row # = p block = f block 1 2 row # -1 3 4 5 6 7 6 7 row # -2

Sample Electron Configurations Europium Tungsten Bismuth Bohrium 1s22s22p63s23p64s23d104p65s24d105p66s25d14f6 1s22s22p63s23p64s23d104p65s24d105p66s25d14f145d3 1s22s22p63s23p64s23d104p65s24d105p66s25d14f145d96p3 1s22s22p63s23p64s23d104p65s24d105p66s25d14f145d96p67s26d15f146d4

Exceptions to the Rules Make sure you know these!! Chromium, Cr Predicted: 1s22s22p63s23p64s23d4 Actual: 1s22s22p63s23p64s13d5 Copper, Cu Predicted: 1s22s22p63s23p64s23d9 Actual: 1s22s22p63s23p64s13d10

Short-Hand Notation [Ne]3s23p2 Noble Gases = He, Ne, Ar, Kr, Xe, Rn Uses a noble gas (Group 18) to represent the innermost electrons. Outermost electrons are represented the same way. Noble Gases = He, Ne, Ar, Kr, Xe, Rn

Short Hand Notation Hints To find the noble gas, look at the noble gas from the previous row or the row above the element. The energy level or coefficient of the s and p-sublevel is equal to the row or period number. The energy level or coefficient of the d-sublevel is one less than the period number and for the f-sublevel two less than the period number.

Sample Electron Configurations Nickel, Ni Antimony, Sb Lead, Pb [Ar]4s23d8 [Kr]5s24d105p3 [Xe]6s25d14f145d96p2 Then combine your d’s! [Xe]6s24f145d106p2

Valence Electrons: Valence Electrons are the electrons in the _______________________ energy level. The energy levels below have the _______________ number of electrons allowed. The number of electrons in the outer level can be found by looking at the highest energy level in the ________________ ____________________ or by looking at the __________________ __________________ located above the column where the element is _________________________. Examples: Mg= Group ___ A so it has _____ valence electrons. Pb= Group ____ A so it has _____ valence electrons.

Label the Valence Electrons for each Column on the Periodic Table

Draw the Lewis Dot Diagrams for the following elements: Sodium Magnesium Aluminum Silicon Phosphorus Sulfur Chlorine Argon

Valence Electrons Electrons in the highest energy level. 1s22s22p63s23p2 What is the highest energy level? n =3 or third energy level How many electrons are on the highest energy level? 4 electrons How many valence electrons are in this element?

One Dot for Each Valence Electron Lewis Dot Diagrams Element Symbol One Dot for Each Valence Electron

How Are the Dots Arranged? 4 8 X 7 1 3 5 6 2

He F Ne C Example Dot Diagrams Write the electron configuration and draw the dot diagrams for each of the following elements. Helium Carbon Fluorine Neon He F C Ne

Short Cut for Valence Electrons 13 IIIA 5 B Boron Use the group number! 13 Al Aluminum 31 Ga Gallium All of the elements in Group 13 or IIIA will have three valence electrons.

Using the Short Cut Using the short cut, determine the number of valence electrons. Phosphorus Argon Lead Barium 5 valence electrons 8 valence electrons 4 valence electrons 2 valence electrons

Exceptions to the Short Cut Only works for Group A Elements or the Representative Elements s and p-blocks ONLY Helium  two valence electrons

Write the electron configuration and draw the Lewis dot diagram for lithium, sodium, and potassium. The arrangement of electrons helps explains the world around us. In this case, all of the Group 1 elements have similar electron configurations, and therefore, have similar chemical properties. Alkali Metals in Water

Rule #1: Pauli’s Exclusion Principle Each atomic orbital can hold two electrons with opposite spins.

Rule #2: Aufbau Principle Electrons will fill the atomic orbital with the lowest energy first. 1s22s22p63s23p64s23d104p5 Lowest Energy  Highest Energy

Equal energy orbitals are orbitals in the same sublevel. Rule #3: Hund’s Rule When filling equal energy orbitals, electrons will arrange themselves to maximize unpaired electrons. Equal energy orbitals are orbitals in the same sublevel.

Orbital Diagrams 3s 2p 1s 2s 1 box = 1 atomic orbital s-sublevel  1 box p-sublevel  3 boxes d-sublevel  5 boxes f-sublevel  7 boxes 1 arrow = 1 electron