2 Outline Electron Dot Symbols Lewis Dot Diagrams Predicting Formulas I. Electronic Structure (CH5)Brief ReviewOrbital DiagramsValence ElectronsAtomic & Ionic RadiiII. Chemical Bonds - Ionic Compounds (CH6)Electron Dot SymbolsLewis Dot DiagramsPredicting Formulas
3 Electron Configuration Write the full electron configuration and the nobel gas shorthand electron configuration for tin (Sn, element 50)
4 Basic Questions about the Model Which of the following orbitals will not be found in our quantum mechanical model?A. 1sB. 3pC. 2fD. 4pJustify your answer based on quantum number rules. When n=2, can only have l=0 (s) and l=1(p) orbitals.
5 Basic Questions about the Model What shell will be the first in which a “4” orbital will be found?n = 4 , l = 0, 1 ,2, 3n = 4 (first time l can equal “3” (f))How many individual orbitals are in the n=2 shell?1 (s), l = 0, ml = (1 value, 1 orbital)3 (p), l = 1, ml = -1, 0, (3 orbitals)TOTAL = 4 orbitals in the n=2 shell
6 Orbital (Box) Diagrams Visual Representations of Electron ConfigurationsEach line (or circle) represents an orbitalArrows represent electronsThe rules of electron configurations are followed1s s 2p s p s
7 Orbital OccupancyThe Maximum Number of Electrons any single orbital can hold is two.They are distinguished from each other an arrow convention - one must be up, one must be down if electrons are in the same orbital.He ____1s
8 Writing Orbital Diagrams Electron configurations tells us which energy levels the electrons for each element are located.THREE rules:1. Electrons fill orbitals starting with lowest energy first2. There can be no more than 2 electrons in any orbital, and those electrons must have different “spins”
9 Writing Orbital Diagrams Electron configurations tells us which energy levels the electrons for each element are located.THREE rules:1. Electrons fill orbitals starting with lowest energy first2. There can be no more than 2 electrons in any orbital, and those electrons must have different “spins”3. For orbitals in the same subshell, electrons fill each orbital singly before any orbital gets a second electron
10 Writing Orbital Diagrams Nitrogen___ ___ ___ ___ ___2s2p1s
12 Learning Check Write the orbital diagrams for: A. oxygen B. phosphorus C. calcium
13 Question!Which electrons are most likely to be involved in chemical reactions?A) those nearest to the nucleusB) those farthest from the nucleusC) all are equally likely to be involved
14 Atomic Families What differentiates one family from another? Li Na K Let’s look at the electron configurations of the alkali metals to find out.LiNaKRbCsFr
15 The Properties of Atoms Are Dependent on Their Valence Electrons Elements that similar properties have the same number of valence electrons!Valence Electrons:For elements in the “s” and “p” block - valence electrons are the electrons in the outer-most electron shell (the shell with the highest n value)Example: Mg: 1s22s22p63s2Example: Cl: 1s22s22p63s23p5
16 How Many Valence Electrons? How many valence electrons do the following elements have?Na: 1Al: 3S: 6Cl: 7
33 Electron Dot SymbolsFocus on valence electrons - highest “n” quantum number for representative elementsElectron Dot Symbols consists of symbol for the element with one dot for each valence e-.Na .
34 Rules for Electron Dot Symbols 1. Representative elements in the same group of the periodic table have the same number of valence electrons2. The number of valence electrons is represented by “dots” around the symbol of the representative element.3. The maximum number of valence electrons for any representative element is 8 - Octet Rule.
36 Octet Rule - What is special about “8”? An octetIs 8 valence electronsIs associated with the stability of the noble gasesHe is stable with two valence electrons (duet).valence electronsHe 1sNe 1s2 2s2 2pAr 1s2 2s2 2p6 3s2 3pKr 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 8
40 Metal Ions – Why Are They Positive? Let’s look at Mg. Its electron configuration is 1s22s22p63s2.If it loses two electrons to become Mg2+, it will have the electron configuration 1s22s22p68 Valence Electrons!If it gains 6 electrons to become Mg6-, it will have the electron configuration 1s22s22p63s23p6The question is which is easier? To lose TWO electrons or to gain SIX?Losing two: Therefore, Mg tends to form Mg2+ ions
42 Nonmetal Ions – Why Are They Negative? Let’s look at Cl. Its electron configuration is 1s22s22p63s23p5.If it loses seven electrons to become Cl7+, it will have the electron configuration 1s22s22p68 Valence Electrons!If it gains 1 electron to become Cl-, it will have the electron configuration 1s22s22p63s23p6The question is which is easier? To lose SEVEN electrons or to gain ONE?Gaining ONE: Therefore, Cl tends to form Cl- ions