Chem 121 1st Edition Lecture 10 Outline of Last LectureI. Aufbau Principle and Electron Configuration ContinuedII. Electron Configuration and Periodic TableOutline of Current Lecture II. Formation of IonsIII. TrendsIV. Ionic Size and Atomic SizeV. Electronic AffinityCurrent LectureFormation of Ions- Metals: Metals lose valence electrons to have the same electron configuration as the immediate proceeding noble gas element. o Group 1A: 1+; Group 2A: 2+; Group (3A): 3+ - Nonmetals: Nonmetals gain as many electrons as needed to have the same electron configuration as the noble gas element (at the end of the period)o Group 7A:1-; Group 6A: 2-; N,P (5A): 3-Trends- Periodical Trends of Atomso Configuration of Valence Electrons determines ALL properties of an element- Periodical Trends of Main-Group Elements (Two factors)o 1. Nuclear charge (Z): Cross period (left to right): Z increases, valence electrons “feel” more attraction from the nucleus Down a group: More number of core electrons, valence electrons “feel” more repulsion (less attraction) from the nucleuso 2. Electron configuration of elements: making individual exceptions- Periodical Trends Among A-Groupso Cross a period (left to right) The greater Z, the more protons The stronger attraction, the smaller the sizeThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. Size goes down as Z increaseso Down a group n increases, size increases Exception: Ga in 3A- Periodical Trends of Ionization Energyo Ionization energy (Ei) : Energy to remove 1 mol e- from 1 mol of atoms or ions First Ei:- Atoms (g) ion+ (g) + e- (g) (ΔE= Ei1 > 0) Second Ei:- Ion+ (g)  Ion2+ (g) + e- (g) (ΔE= Ei2 > Ei1 > 0)o Ei and Chemical Properties Ei: positive (absorbs energy to remove electrons) Elements: Low Eilose e- easily become cations (+) Electron Removed: one at highest energy level to move first- Periodical Trends of Ionization Energyo Ei1 vs. Z – The higher the Z, the higher Ei1o Trends in Ei1 in A-Groups Down a group: Ei1 decreases as size increases- Except 3A- Ga, In, TI Cross a period (Left to Right): Ei1 increases as Z increases- Exceptions: o Dips:  3A: ns2np1  (losing 1 e-) 3A: ns2  6A: ns2np4  (losing 1 e-) 6A: ns2np3 These become more stable (Half) full subshell after losing e- makes atoms easier to lose e-Ionic Size and Atomic Size- Ionic Radius- estimate value from crystalline ionic compounds- Ionic Radius vs. Atomic radiuso rcation < ratom , ranion > ratom ( The more electrons, the more repulsion)- Trends of Ionic Size: o Down a group (down columns): ionic size increaseso Cross a period (left to right): Cation size increases, Anion size decreaseso Isoelectronic (same # of electrons) ions: 3- > 2- > 1- > 1+ > 2+ > 3+o Element with 2 or more cations: The greater the charge, the smaller the cationElectronic Affinity- Electronic Affinity (EA): is energy change (in KJ/mol) for adding 1 mol electron to 1 mol of gaseous atoms or ionso Atom (g) + e-  ion- (g) (ΔE= EEA)o Heat release (-) for most elements: most atoms welcome e-o Heat absorption (+) for 8Ao General Patterns (except 8A) Results of Z= electron configuration- Down a group, EA gets weaker- Cross a period (left to right) EA gets stronger, more “-“ Major Exceptions1. 2A: ns2 – full subshell (no need for more e-)5A: ns2np3 -half-full subshell (no need for more e-)2. B, C, N ,O, F: smallest sizes, stronger