Transcript Period
The Periodic Law – Chapter 5 What does the word “periodic” mean? • Periodic: Mendeleev 1869 • Arranged elements according to _______________________ • Put elements of similar properties in the same_______________________ • Why did he leave blank spots in table? 2 questions ….. 1. Why could most elements be arranged in order of increasing atomic mass but a few could not? (Te & I, Co & Ni, Ar & K) 2. What was the REASON for chemical periodicity? Henry Mosley 1911 (40+ years later)… • Used X-ray and spectral studies to show that each element has ________________ • ___________________ is a better basis for organizing the Periodic Table Periodic Law • The physical and chemical properties of the elements are periodic functions of their___________ Modern Periodic Table • An arrangement of the elements in order of their______________ so that elements with similar properties fall in the same___________, or _____________ Noble Gases • Proposed by Sir William Ramsay and John William Strutt • Lack of chemical ______________ The Lanthanides • The 14 elements with atomic numbers from 58(cerium, Ce) to 71(lutetium, Lr) • Similar in__________ and___________ properties The Actinides • The 14 elements with atomic number from 90(thorium, Th) to 103(lawrencium, Lr) Periodicity • Figure 5-4 on page 126 • Periodicity is explained by the arrangement of the________________around the nucleus 5-2 Electron Configuration and The Periodic Table What is the outer configuration of the following: • Re (#75) • I (#53) • Cd (#48) Which sublevel fills in after the… • 4s • 4d • 6s • 5p 5-3 Electron Configurations and Periodic Properties Atomic Radius • One-half the distance between the nuclei of identical atoms that are bonded together Group Trend for Atomic Radii • Down a group the radius of an atom gets ……..…. because… Period Trend for Atomic Radii • Across a period the radius of an atom gets ………………....because…. • Exception: Noble Gas Family – atoms don’t interact and pull together like in other atoms because__ Why does the atomic radii not decrease very much as you move across the d-sublevel? Why would the atomic radius of hafnium (#72) be LESS than that of zirconium (#40)? Ionization energy, IE • Energy required to _________ an electron from a neutral atom (or first ionization energy, IE1) • __________: charged particle • _______________: process of an electron being lost or gained from an atom which results in the formation of an ion Group Trend for Ionization Energies • Down a group the ionization energy of an atom generally gets ………………… because…. Period Trend for Ionization Energies • Across a period the ionization energy …….…..because 4 Factors Affecting Ionization Energy Multiple Ionization Energies • Energy required to remove the 2nd, 3rd, etc. electron from an atom • IE3……. IE2….. IE1 because ……… Why does the IE go UP as you go down a d-sublevel group but go down in an s sublevel? Electron Affinity p. 147 • Energy change the occurs when an _______ ___________________ by a neutral atom • Most atoms _______ energy when they acquire an electron: A + e- A- + energy – energy has _____sign • Some atoms ________ energy when they acquire an electron: A + e- + energy A– energy has ______ sign; atom is unstable & loses electron spontaneously Group Trend for Electron Affinities • Down a group the electron affinity of an atom tends to get …………….because Period Trend for Electron Affinity • Across the p-sublevel, the energy change ………………(becomes more …………..) because….. Why is the electron affinity of nitrogen so low when compared to carbon or oxygen? Multiple Electron Affinities • It is always ……………….. to add a 2nd electron to an already negatively charged ion..therefore, all 2nd electron affinities are ………………….. Ionic Radii • Cation: • _________ ion • Formed by an atom …………. electron(s) • Always …………. because electron cloud is smaller (less repulsion) & sometimes even one less energy level! • Anion: • __________ ion • Formed by an atom …………… electron(s) • Always …………. because electron cloud is greater (more repulsion among electrons) Group Trend for Ionic Radii • Down a group the ionic radius of an atom generally gets ……………because . Period Trend for Ionic Radii • Metals (left side):form ……………. – Cationic Radius: ………….. ionic radius as nuclear charge increases without adding an energy level • Non-metals: form ……………… – Anionic Radius:……………………. ionic radius as nuclear charge increases without adding an energy level Valence Electrons • Electrons available to be lost, gained, or shared in the formation of chemical compounds • Often the outermost electrons because they are held most loosely What would be the # of valence electrons in…….. • • • • Calcium Lithium Chlorine carbon What would be the # of valence electrons in…….. • • • • Calcium – 2 : 4s2 Lithium – 1: 2s1 Chlorine – 7: 3s23p5 Carbon – 4: 2s22p2 Electronegativity • Measure of the ability of an atom ______ ___________________to attract electrons • ___________________ is the MOST electronegative element – assigned an arbitrary value of ______ • All other values are relative to F • 3 highest values: F – O - N Group Trend for Electronegativity • Tend to ___________ down a group (or stay the same) as the atoms gets larger Period Trend for Electronegativity • Tend to _______________ across the period as the atoms gets ________, the nuclear charge becomes ___________, and the atom is getting closer to a noble gas configuration Determine the likely charge for the following elements: Ca, O, Al 1. Write the noble gas configuration of the element 2. Determine if electrons will be LOST or GAINED to make the element stable 3. ID the noble gas whose electron configuration by losing/gaining these electrons 4. Write the formula for the ion 5. ID it as a cation anion How do d-block elements form ions? • Electrons in the highest occupied sublevel are always removed first Why does zinc become a +2 ion? Which electrons are lost when titanium becomes a +2, a +3 and a +4 ion?