Transcript File
Orbital Diagrams Electrons are organized in four ways 1st = Energy levels or shells 4th = Spin ‘up’ or ‘down’ 1,2,3,4,etc 2nd = Sublevels or subshells each energy level contain sublevels called s,p,d,f 3rd = Orbitals each sublevel contain orbitals (different # for different sublevel) Definition: an orbital is the space occupied by two (a pair of) electrons Electron Sublevels s p d f On all energy levels 1 orbital On energy levels 2 and up 3 orbitals On energy levels 3 and up 5 orbitals On energy levels 4 and up 7 orbitals holds 2 e- holds 6 e- holds 10 e- holds 14 e- What do orbitals look like? orbital on s sublevel (one per sublevel) orbitals on p sublevel (three per sublevel) (remember two electrons fit in each orbital) What do orbitals look like? orbitals on d sublevel (five per sublevel) What do orbitals look like? orbitals on f sublevel (seven per sublevel) Practice – Rally Coach • There are 8 questions on the next slide • Working with your FACE partner, alternate stating the answers to questions, B starts – The second person should agree with the answer before moving on to the next question – If you don’t know, have your partner give you a tip to help you figure it out B: How many electrons can a p sublevel hold? A: Name the sublevels. B: What energy level does sublevel d start on? A: How many electrons can the third energy level hold? B: How many orbitals are in a d sublevel? A: How many electrons can an p sublevel hold? B: How are energy levels labeled? A: What energy level does sublevel f start on? 1. 2. 3. 4. 5. 6. 7. 8. How many electrons can a p sublevel hold? 6 Name the sublevels. s, p, d, f What energy level does sublevel d start on? 3 How many electrons can the third energy level hold? 18 (2 in s + 6 in p + 10 in d) How many orbitals are in a d sublevel? 5 How many electrons can an s sublevel hold? 2 How are energy levels labeled? Integer numbers What energy level does sublevel f start on? 4 Since sublevels and orbitals are too complicated to draw all the time, we simplify with orbital diagrams. Each orbital is represented by a box or a line. or _______ Each electron is represented by an up or down arrow. (means 2 electrons) s sublevel s sublevel has one orbital, so we draw one box. p sublevel p sublevel has 3 orbitals, so we draw 3 boxes. d sublevel d sublevel has 5 orbitals, so we draw 5 boxes. f sublevel f sublevel has 7 orbitals, so we draw 7 boxes. Orbital and sublevel information is like a map, telling you where an electron can be found in an atom. There are three rules that govern why an electron will be in one sublevel rather than another: 1.Pauli Exclusion Principle 2.Hund’s Rule 3.Aufbau Principle Pauli Exclusion Principle: No two electrons can be organized in exactly the same way (E.L, sublevel, orbital, spin). What that means is that 2 electrons may occupy one orbital, but they must have opposite spin direction. This is why we draw electrons as arrows facing opposite directions when they share a box: WRONG! RIGHT! Hund’s Rule of Maximum Multiplicity: Electrons occupy vacant orbitals before pairing Example: 4 electrons in a d sublevel WRONG -This is not as stable. Electrons repel each other. RIGHT -This is stable. Hund’s Rule paraphrased – spread them out before you pair them up! Aufbau Principle: Each electron must occupy the lowest energy orbital available. Not all sublevels and orbitals have the same energy! s p d f energy increases 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p This chart shows the order that electrons fill sublevels. Although the d and f sublevels are on lower energy levels, they have high energy and do not fill until after the s and p for higher energy levels. The number of columns in each block corresponds to the number of electrons that fit in that sublevel You can use the periodic table like a game board to see the order in which the sublevels fill. The period number tells you the energy level (for s and p) Each square can mean the position of one electron The block tells you the sublevels An element’s location within the block tells you how many electrons it has in that sublevel Example: Nitrogen is in the 3rd column of the p block. It has 3 electrons in the 2p sublevel Rally Coach – A starts, Face Partner • To which sublevel do we go after filling 4s? • To which sublevel do we go after filling the 6s? • To which sublevel do we go after filling the 4d? • To which sublevel do we go after filling the 2s? • Where do electrons 88-90 go? Rally Coach – A starts, Face Partner • To which sublevel do we go after filling 4s? 3d • To which sublevel do we go after filling the 6s? 5d • To which sublevel do we go after filling the 4d? 5p • To which sublevel do we go after filling the 2s? 2p • Where do electrons 88-90 go? 88 is 7s, 89 is 6d, 90 is 5f Example: Manganese has 25 electrons. Draw its orbital diagram. 1s 4s 2s 2p 3s 3p 3d Use Aufbau Principle to decide which order to fill sublevels, Pauli Exclusion Principle to place arrows in opposite directions in each orbital, Hund’s Rule to spread out before pairing up! Example: Manganese has 25 electrons. Draw its orbital diagram. 1s 4s 2s 2p 3s 3p 3d Use Aufbau Principle to decide which order to fill sublevels, Pauli Exclusion Principle to place arrows in opposite directions in each orbital, Hund’s Rule to spread out before pairing up! An easy way to remember… First write columns for sublevels 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 7p 3d 4d 5d 6d 7d 4f 5f 6f 7f This is a diagram of the Aufbau Order (order of filling in electrons) *because no known element has enough electrons to start filling 6f and up, we can omit those levels in the future! Then draw in diagonals starting with lowest energy level 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 7p 3d 4d 5d 6d 4f 5f I n c r e a s i n g E n e r g y Practice • Individually: write the orbital diagram for – Arsenic – Switch papers with your shoulder partner and check for accuracy (correct/celebrate) • Individually: write the orbital diagram for – Strontium – Switch papers with your face partner and check for accuracy Electron Configuration Electron Configurations • Draw the orbital diagram for calcium. 1s 2s 2p 3s 3p 4s Shorthand Electron Configuration • In Aufbau order of filling electrons for Ca 1s2 2s2 2p6 3s2 3p6 4s2 • Superscripts are number of electrons in that sublevel • How many electrons does this neutral atom have? 1s2 2s2 2p6 3s2 3p6 4s1 2+2+6+2+6+1= 19 • What element is it? potassium electrons Writing Electron Configuration • Always fill electron orbitals in Aufbau Order • When you write your final electron configuration, put them in the same order electrons fill: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 Now you practice! • Write the electron configuration for indium. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p1 • Write the electron configuration for tantalum. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d3 (or it can end 6s2 5d34f14) Your Turn: Cobalt has 27 electrons. Draw its orbital diagram. Then, write its shorthand electron configuration. On your notecard 1. Write the orbital diagram for selenium 2. Write the electron configuration for barium 3. Circle the valence electrons for #1 and #2 Ions and Exceptions What are ions? • Ions have lost or gained electrons • Gained electrons = anions, negatively charged • Lost electrons = cations, positively charged Anions • If an atom gains one additional electron, just follow the aufbau rules to put the electron in its proper location • For example: Cl-1 1. Write the electron configuration for the neutral atom: Cl: 1s22s22p63s23p5 2. Add the addition electrons into the vacant orbitals (put the extra in the 3p) Cl -1: 1s22s22p63s23p6 Anions • What if it gains 2 electrons? • For example: O2• (Neutral) O: 1s22s22p4 • (Anion) O2-: 1s22s22p6 What do you notice about anions? They always have electron configurations that look like noble gases! Cations • If an atom loses one electron, you must take the electron from the highest energy sublevel! • For example: Na+1 1. Write the electron configuration for the neutral atom: Na: 1s22s22p63s1 2. The highest energy sublevel is the 3s, so remove the electron from there Na+1: 1s22s22p6 Cations • Remember, you must take the electrons from the highest energy sublevel! • For example: Ti2+ 1. Write the electron configuration for the neutral atom: Ti: 1s22s22p63s23p64s23d2 2. The highest energy sublevel is the 4s, so remove the electrons from there Ti2+: 1s22s22p63s23p63d2 Valence Electrons • • • • • • Electrons in the highest ENERGY LEVEL Let’s practice with the examples so far: Cl-1 = O2- = Na+1 = Ti2+ = Valence Electrons • • • • • • Electrons in the highest ENERGY LEVEL Let’s practice with the examples so far: Cl-1 = 8 O2- = 8 Na+1 = 8 Ti2+ = 10 exit quiz • Write the electron configuration of tungsten(VI) and identify the number of valence electrons [tungsten(VI) = W+6] – Circle the number of valence electrons so it is easy to find • Draw the orbital diagram for sulfide Quantum numbers are like an address… Recap • Quantum numbers are just addresses for electrons • Each electron has four numbers that tell you: – Energy level (n) – Sublevel (l) • Just remember the code: 0=s, 1=p, 2=d, 3=f – Orbital (ml) • Always number it like a number line with zero in the middle – Spin (ms) • +1/2 for the up arrow • -1/2 for the down arrow You need a board/marker/eraser 1s 2s 2p 3s 3p We usually only ask about the ‘last electron filled’ but every electron has a set of quantum numbers Which electron is the last electron filled? What are the quantum numbers for that electron? -1 1s 2s 2p 3s 0 1 3p We usually only ask about the ‘last electron filled’ but every electron has a set of quantum numbers Which electron is the last electron filled? What are the quantum numbers for that electron? 1s 2s 2p 3s 3p What are the quantum numbers for this electron? Answer: 3,0,0,1/2 What are the quantum numbers for the last electron filled in zinc? [Hint: start with an orbital diagram] Answer: 3,2,2,-1/2 What are the quantum number(s) for the valence electron(s) of strontium? Answers: 5,0,0,1/2 and 5,0,0,-1/2 (the two electrons in the 5s) What are the quantum number(s) for the valence electron(s) of titanium(I)? Answer: 4,0,0,1/2 The electron configuration for neutral Ti ends in 4s23d2. The electron configuration for Ti+ ends in 4s13d2. The valence electron is the 4s1 electron. How many electrons have n=2? Answer: 8 n=energy level 2 has 2s (2 electrons) + 2p (6 electrons) How many electrons could be described using n=3 and l=2? 3,2 would indicate 3d Answer: 10 electrons fit in the 3d Review • You’ll need a piece of paper and your periodic table • There are 29 problems scattered around the back tables • You may work alone or in pairs (anyone from the class), no groups of 3 or more • Move around answering questions • When you finish, sit down and start on your homework – We will go over answers when everyone has finished (or next class if we run out of time)