Periodic Trends - Oak Park USD

November 07, 2014Periodic TrendsRemember from the "Periodic Table" Notes. The periodic table is a tabular display of the chemicalelements, organized by their atomic number, electronconfiguration, and recurring properties. Periodic law: There is a periodic repetition ofchemical and physical properties of the elements whenthey are arranged by increasing atomic number

November 07, 2014Atomic Radius Graph What are some initial observations about the atomicradius data/graph? What is atomic radius?

November 07, 2014Go finish the rest of the worksheet with yourgroup! You have 20 minutes.

November 07, 2014Atomic Radius Trend Discussion What happens to atomic radius as you go across theperiod? Why? What happens to atomic radius as you go down thegroup? Why?

November 07, 2014Periodic Trends NotesGet your handout out!

November 07, 2014Why is it called a periodic table? The properties of the elements in the table repeat in a"periodic" way (specific pattern). Periodic law: There is a periodic repetition of chemicaland physical properties of the elements when they arearranged by increasing atomic number The modern periodic table is arranged by atomic number # of protons properties electron configuration

November 07, 2014Periodic Law Now lets look at some properties of elements We looked at some of these in "Meet My Family"!Alkali MetalsHalogens

November 07, 2014Periodic Trends Chemical properties of elements are determined bytheir electron configuration. Properties are periodic because the number of valenceelectrons is periodic.

November 07, 2014Electron Configuration and the Periodic Table Remember electrons are found in atomic orbitals Principle energy level (n, shells) tells us therelative size and energy of atomic orbitals. Each shell can hold a certain number of electrons. # of e- # of p for a neutral atom Valence electrons electrons in outermost shell232188

November 07, 2014Electron Configuration and the Periodic Table If we draw these orbital diagrams for H, He, Li, Be Na,Mg,232188

November 07, 2014Electron Configuration and the Periodic Table Periods: Period equals the highest principle energylevel of electrons (shell of the valence electrons) Groups: Elements in the same group have the samenumber of valence electrons

November 07, 2014Now lets look at two trends1. Atomic radius2. Ionization energy

November 07, 20141. Atomic RadiusThe electron cloud surrounding a nucleus is based onprobability and does not have a clearly defined edge. Atomic radius: half the distance between nuclei ofadjacent identical atoms Adjacent nuclei in a crystal Nuclei of two atoms bonded togetherhttp://en.wikibooks.org/wiki/High School Chemistry/Atomic Size

November 07, 2014Atomic Radius Atomic radius is determined by the strength ofattraction between the valence electrons and thenucleus # of protons in nucleus # of shielding electrons that "block" protons fromvalence electrons

November 07, 2014Atomic Radius Trend What happens to atomic radius as you go across theperiod? What happens to atomic radius as you go down thegroup?

November 07, 2014So why does the atomic radius. Decrease across a period? Increase down a ples%20Chem/atoms/atomperiodic.htm

November 07, 2014Atomic Radius Moving down a group: Atomic radius increases Principal energy levels increase (bigger shell) increased orbital size, electrons are farther m

November 07, 2014Atomic Radius Moving across a period: Atomic radius decreases Principal energy level remains the same # of protons increases: electrons pulled in riodic.htmhttp://chemwiki.ucdavis.edu/

November 07, 2014Example 1: Order the following atoms from smallest tobiggest atomic radius:Ga, Se, KI, F, Cl

November 07, 20142. Ionization Energy Ionization energy energy required to removean electron from a gaseous atom. (kJ/mol)When you remove anelectron from an atom,what do you get?

November 07, 2014Ionization energy Ionization energy is an indication of how strongly anatom's nucleus holds onto its valence electrons Greater IE harder to ionize Ionization energy is always a positive value You can take off more than one electron! IE1 (1st ionization energy) energy required toremove 1st valence e IE2 (2nd ionization energy) energy required toremove a 2nd e-NaNa e-H 495.8 kJ/molMgMg e-H 737.7 kJ/molMg Mg2 e-H 1450.6 kJ/mol

November 07, 2014Ionization Energy Is an atom with a high ionization energy more likelyor less likely to form a positive ion? What about one with low ionization energy?What is the periodic trend forionization energy?What factors affect ionization energy?

November 07, 2014Ionization EnergyWhat patterndo you see?

November 07, 2014Ionization Energy Moving down a group: IE decreases There are more electrons in between the nucleusand the valence electrons (shielding effect) Electrons are not as tightly bound to nucleus. Electrons are further away, attraction decreases. Moving across a period: IE increases Increased nuclear charge (more p , greaterattractive force)

November 07, 2014Ionization Energy What about successive IE (removing more than one e-)? Successive IE increases There is a big "jump" in some IE required. Why? W/in a sublevel: small increases Between sublevels: greater increase Between energy levels: greatest increasehttp://www.avon-chemistry.com/p table lecture.html

November 07, 2014Example 2:In the following pairs, which atom is moredifficult to ionize/Has the higher IE?Na or LiNa or MgC or NaCl or Al

November 07, 2014Using these trends, can you explain thealkali metal reactions?

Periodic Trends Remember from the "Periodic Table" Notes. The periodic table is a tabular display of the chemical elements, organized by their atomic number, electron configuration, and recurring properties. Periodic law: There is a periodic repetition of chemical and physical properties of the elements when