Documents about Effective Nuclear Charge

  • 3 Pages

    lec24_post

    Iowa State, CHEM 177

    Excerpt: ... Announcements To be added. Periodic Table A key development for understanding chemistry Several tried to come up with it John Newlands was literally laughed out of the Royal Society (of London) for suggesting "Law of Octaves" Mendeleev went further A key success One reason the atomic model was accepted was the way it meshed with the periodic table We will look at several observable properties. First - looking at details about electrons. Force of attraction Negative charged electrons are attracted to the positive nucleus. But, other electrons are present as well. The inner electrons are between the outer electrons and the nucleus They shield part of the charge. Effective nuclear charge An estimate of the positive charge actually present for outside electrons Zeff = Z - S Z = atomic number S = # of inner (core) electrons Examples What is the effective nuclear charge of a valence electron in Be? What is the effective nuclear charge of a valence electron in ? What is th ...

  • 2 Pages

    10-28_163

    Iowa State, CHEM 163

    Excerpt: ... on the periodic table: EA become increasingly negative. This does NOT include noble gases we pointed out that ALL noble gases have very large very positive electron affinities and have no desire to accept an additional electron. The largest most positive value of EA in any period or row belongs to the noble gas. We stated: a negative EA means that when an electron is added energy is released so atoms who want additional electrons have negative EA (halogens). Atoms who do not want additional electrons added have positive values of EA. We correlated trends in electron affinities with the formation of cations versus anions in ionic compounds. We also correlated trends in electron affinities with the effective nuclear charge atoms whose valence electrons experience large effective nuclear charge s (except noble gases) have negative electron affinities and those who have small effective nuclear charge s have positive electron affinities. Noble gases have very positive electron affinities because the additiona ...

  • 10 Pages

    ln5f07

    University of Texas, CH 301

    Excerpt: ... LECTURE 5. PERIODIC TRENDS EXPLAINED BY EFFECTIVE NUCLEAR CHARGE Summary. The periodic table was created as a consequence of the boundary conditions imposed by the quantum mechanical solutions to Schrodingers wave equations for multi-electron systems. What we will learn in this lecture is that in defining the properties of atoms and ions in the table, there will turn out to be periodic trends to those properties. Specifically, we will see that as we go across the table from left to right, or down the table from top to bottom, we will see that a systematic increase or decrease in the quantitative measure of a property is observed. This is good for two reasons. First, allows us to cement into place the important ideas that explain the properties. And second, it keeps us from having to to much memorization since we can make nice sweeping generalizations. What are the trends that we will be able to explain? There are a lot of them. But here are six you will see over the next several lectures: Atomic radius ...

  • 15 Pages

    Chem_110_Fall_Booker_Lec6_7

    Penn State, CHEM 110

    Excerpt: ... Periodic Properties of the Elements (Lecture 7) Row called a Period Column called a Group or Family Electron Configuration and the Periodic Table Location on the Periodic Table is related to electron configuration Valence orbitals are those that contain the outer shell of electrons Electrons in valence orbitals are those that are involved in bonding. Elements in the same Group (column) of the Periodic Table contain the same number of electrons in their valence orbitals. (H) Li Na K Rb 1s1 [He]2s1 [Ne]3s1 [Ar]4s1 [Kr]5s1 Effective Nuclear Charge Electrons in inner core shield outer electrons from full positive charge of nucleus. The actual nuclear charge felt by any given electron is called the effective charge (Zeff) Zeff can be approximated by the equation: Zeff = Z S; Z = nuclear charge (i.e. number of protons) S = screening constant (approximated as number of core electrons between elecron of interest) Electrons of same n value dont screen as well. Trends in Effective Nuclear Charge ...

  • 12 Pages

    Review1

    Virgin Islands, CHEM 101

    Excerpt: ... easing atomic number, not atomic weight. The modern periodic table is arranged according to increasing atomic number, and consists of vertical groups (or families) and horizontal periods. (See pages 262-263 in the text.) 4 12/2/2008 II. Effective Nuclear Charge Effective Nuclear Charge - In multielectron atoms, the electron-to-electron repulsions reduce the strength of the nuclear charge felt by the electrons. The effective nuclear charge , Zeff, is the net nuclear charge actually felt by an electron, and is calculated as follows: Zeff = Z (the number of protons) S (the electron shielding constant) Periodic Trends in Effective Nuclear Charge The effective nuclear charge , Zeff, increases as we move from left to right across the periodic table, but decrease as we move from top to bottom. (See pages 264-265.) Sizes of Atoms and Ions Atomic Radii generally decrease from left to right and increase from top to bottom. (Do Sample Exercise 7.2 without looking at the solution.) Ionic Radii depend on the type a ...

  • 42 Pages

    chapter7

    Illinois State, CHE 140

    Excerpt: ... velopment of the Periodic Table Periodic Properties These are properties of elements that can be rationalized in terms of the element position in the periodic table. We will study: Atomic and Ionic Size Ionization Energy Electron Affinity Metallic Character Atomic Orbitals Electron Shells in Atoms are called Orbitals An orbital is the probability of finding an electron around the nucleus. Shown is an Electron density plot, which is the graphical representation of an orbital The shape and size of an orbital is defined by a set of quantum numbers. In general, the size of an orbital increases, as the principal quantum number (n) increases. Within the periodic table, the period (row) indicates the value of n number. Size of Atomic Orbitals Consider the s orbitals: All s orbitals are spherical and increase in size as n increases. Effective Nuclear Charge Effective nuclear charge is the actual nuclear charge experienced by an electron in an atom. Consider the outermost electron in the atom: The ch ...

  • 2 Pages

    chem 141 F07 Chapter 8 Study Sheet

    Emory, CHEM 141

    Excerpt: ... bering system. 1 Modified from Change, R. Chemistry 6/e 1998 p.287. DEFINITIONS You should have a working knowledge of at least these terms and any others used in lecture. Covalent radius Metallic radius Ionic radius Diamagnetic Paramagnetic Ionization energy Electron affinity Periodic law Electron configuration Effective nuclear charge Isoelectronic Aufbau principle Transition elements Main group s-, p-, d-, f-block elements Lanthanides Actinides Halogens Noble gases Calcogens Alkali metals Alkaline earth Law of octaves Law of triads ...

  • 3 Pages

    lec24_long_post

    Iowa State, CHEM 177

    Excerpt: ... Announcements To be added. Periodic Table A key development for understanding chemistry Several tried to come up with it John Newlands was literally laughed out of the Royal Society (of London) for suggesting "Law of Octaves" Mendeleev went further Predicted elements not yet discovered. A key success One reason the atomic model was accepted was the way it meshed with the periodic table We will look at several observable properties. First - looking at details about electrons. Recall effective nuclear charge An estimate of the positive charge actually present for outside electrons Zeff = Z - S Z = atomic number S = # of inner (core) electrons Examples What is the effective nuclear charge of a valence electron in Be? What is the effective nuclear charge of a valence electron in ? What is the effective nuclear charge of a valence electron in ? Trend Effective nuclear charge increases from left to right in a period. Atomic properties How should effective nuclear charge eff ...

  • 2 Pages

    6_19_177

    Iowa State, CHEM 177

    Excerpt: ... View Message https:/webct.its.iastate.edu/webct/urw/lc642954443071.tp65390792105. Close this window Help Message previous | next Reply Reply to All Forward Print Delete Sent: June 19, 2008 12:22 PM To: All Section Instructors; All Section Designers; All Teaching Assistants; All Students; All Auditors CC: Subject: Announcements 177 6/19 From: Joseph Burnett Che c' di nuovo? Mastering Chemistry assignment 21 is due tomorrow morning it covers atomic radii, effective nuclear charge and ionization energies. Preparation for exam II: there are several optional assignments on Mastering Chemistry that cover solutions & solution stoichiometry and thermochemistry. Reviews for exam II: a) Friday 11:15 AM in 1002 Gilman b) Sunday 6:10 PM in 1002 Gilman The following is from http:/scienceworld.wolfram.com/biography/Newlands.html "John Alexander Reina Newlands - English chemist who in 1863 proposed the Law of Octaves which stated that chemical properties repeated with every eighth element. Because Newlands ...

  • 1 Pages

    Key_points_for_chapter_7_08

    SUNY Albany, CHM 120

    Excerpt: ... Key Points for Study Chapter 7: Periodic Properties of Elements I. Key points to pay attention: How position on the periodic table and electron configurations can be used to highlight periodic properties, not so much about the absolute values but rather, the trend or the periodic pattern. You may find the descriptive chemistry/group trends a bit overwhelming at first. However, the periodic table IS REALLY an organizational tool; it will help you recall chemical facts. The sign convention for electron affinities should not be confused. II. Understand clearly the terms and concepts summarized at the end of the chapter in the book. The following are some specific points I wish to emphasize, and you must handle these concepts and skills: 1. Effective nuclear charge . Know how to calculate effective nuclear charge given an element (think about a more basic question: why is it that we need to introduce the effective nuclear charge - see the following periodic properties) 2. Be able to predict the size of i ...

  • 4 Pages

    Lecture 6 NotesThe Periodic Table and Atomic Co...

    University of Texas, CH 53750

    Excerpt: ... iscussion. Electronic shielding will be employed to explain the atomic trends that we will discuss below. Think of the atom as a rock concertthere is a stage with the band (nuclear protons) and rows of seats (electronic shells) with screaming fans (the electrons). Just as in a rock concertthe closest row can be thought of as the best seat in the house (they get the full experience of the show) while the back row isnt very good (too many screaming fans blocking the view). This is analogous to atomselectrons in the innermost shell feel the full nuclear force while electrons in the outermost shell will feel a somewhat reduced nuclear force (called the effective nuclear charge (E.N.C.) because other electrons lie in the intervening shells and block a portion of the nucleus pull. It is important to note that electrons in your same shell will not shield other electrons in the same shell (fans in the same row as you will in general not hinder your ability to enjoy the concert). So ...

  • 70 Pages

    BLB6S

    SUNY Buffalo, CHE 101

    Excerpt: ... o allowed values of ml of -1, 0, and +1.) The orbitals are dumbbell shaped. As n increases, the p-orbitals get larger. All p-orbitals have a node at the nucleus. Chapter 5 48 Representation of Orbitals The p Orbitals Chapter 5 49 Representation of Orbitals The d and f Orbitals There are 5 d- and 7 f-orbitals. Three of the d-orbitals lie in a plane bisecting the x-, yand z-axes. Two of the d-orbitals lie in a plane aligned along the x-, y- and z-axes. Four of the d-orbitals have four lobes each. One d-orbital has two lobes and a collar. Chapter 5 50 Representation of Orbitals The d Orbitals Chapter 5 51 Orbitals in Many Electron Atoms Orbitals of the same energy are said to be degenerate. For n 2, the s- and p-orbitals are no longer degenerate because the electrons interact with each other. Therefore, the Aufbau diagram looks slightly different for many-electron systems. Effective Nuclear Charge Effective nuclear charge is the charge experienced by an electron ...

  • 12 Pages

    205_W08_03_lecture_20

    Concordia Canada, CHEM 205

    Excerpt: ... me # of e-s E.g.: species described by same noble gas configuration 1s2 2s2 2p6 = Ne, F-, O2-. Na+, Mg2+, Al3+ (10) Configurations of d-block transition-metal ions For d-shells: emptying order is not same as filling order. s subshell loses e-s before d subshell. To predict the e- configuration of a transition-metal cation: remove valence e-s from subshell with highest n value 1st. BASED ON EXPERIMENTAL EVIDENCE: Chemical & physical properties of transition-metal cations are characteristic of having valence of d-electrons, not s. Co: [Ar]3d74s2 lose 2e VALENCE: PER ION: EVIDENCE: Co2+: [Ar]3d7 3d 3 unpaired e-s Paramagnetic NOT Co2+: [Ar]4s23d5 4s 3d 5 unpaired e-s Paramagnetic.but, greater attraction to magnetic field than is actually observed. (11) 8.6 Periodic trends in properties Atomic & ionic size Ionization energy Electron affinity EXPLAINED using effective nuclear charge , estimated by: 1.) calculating Zeffmin (how much + charge do the e-s feel?) AND 2.) considering orbital siz ...

  • 3 Pages

    Study Guide Exam 3

    UC Riverside, CHEM 1A

    Excerpt: ... be able to predict relative sizes. Terms: All terms except: effective nuclear charge , penetration, and amphoteric. Study Guide Exam III.doc Page 2 ...

  • 35 Pages

    11

    SUNY Albany, CHM 120

    Excerpt: ... se nodes? Atomic Orbitals of Hydrogen-like Atoms Hydrogen-like Atoms For an atom or ion with one electron orbiting a nucleus of charge Z The orbital energies are given by En = -Z2hcRH(1/n2) where n is the principal quantum number (i.e., n = 1, 2, 3, .), and RH is the Rydberg constant = 1.096776 107 m-1. Hydrogen and Helium Ground States Hydrogen atom Helium positive ion Helium atom Orbitals in Many Electron Atoms Effective nuclear charge is the charge experienced by an electron in an orbital on a many-electron atom. The effective nuclear charge is less than the charge on the nucleus because of the shielding effect of inner electrons. Electrons in outer orbitals are attracted to the nucleus, but repelled by electrons in inner orbitals that screen them from the nuclear charge. As the average number of screening electrons (S) increases, the effective nuclear charge (Zeff) decreases. Orbitals in Many Electron Atoms Question In the chlorine atom ...

  • 3 Pages

    Lect16_Hatom3

    Wisconsin, CHEM 562

    Excerpt: ... istance between electron i and the nucleus. (3) ^ ^ ^ hei = Tei + VN ei = - 2 (4) With this separable Hamiltonian, as we have learned before, the total electronic wavefunction is the product of the one-electron wavefunctions and the total electronic energy is just the sum of one-electron energy: approx (r1 , r2 ) = H (r1 ) H (r2 ) 1 (5) H H E approx = E1 + E2 (6) where H (ri ) and EiH are nothing but the atomic orbital and electronic energy of a hydrogenic ^ atom (because the hei is just the Hamiltonian of a hydrogenic atom)! Question: Can you generalize this to many-electron atoms? One issue that we have to worry about, however, is how to "fill up" the hydrogenic atomic orbitals when there are many electrons in the atom. To consider the aufbau (Germane for "build-up" principle), we need to think about a few issues: 1. Pauli-exclusion principle - which is due to the symmetry requirement on indistinguishablefermion wavefunction 2. Screening and effective nuclear charge 3. Hund's rule - arises due t ...

  • 17 Pages

    Chem121-Chapter-7-SH

    Ohio State, CHEM 121

    Excerpt: ... Chapter 7 Periodic Properties of the Elements R. Spinney 2009 Introduction Quantum Mechanics describes the electronic structure of atoms which correlates with the arrangement of the Periodic Table. This connection between electronic structure and chemical & physical properties allows us to make general statements about a number of properties of atom based to their position in the periodic table. A number of elements were discovered based on expected predictions of these missing elements! Effective Nuclear Charge As we have seen, in poly e- atoms, the subshells for any given n have different E This is due to the different e- - e- repulsions for ein different subshells. In addition we have subsets of e-; 1) core e-: 2) valence shell e-: Effective Nuclear Charge (contd) Primary interaction of e- & nucleus is due to charge: Coulombs Law: F = (kQeQn)/r2 However, the valence shell e- do not experience the full nuclear charge, they are shielded by the core e- Effective Nuclear Charge (contd) ...

  • 3 Pages

    QuizF1

    LSU, CHEM 1201

    Excerpt: ... Study Guide for Timed Quiz 9 Study the concepts on the WebChemTutor first. Then take this practice quiz and review the solutions. Please review the solutions for all problems even if you got the problem correct! 1. Review WebChemTutor Ch 3: Limiting Reagent Calculations and Experimental Yield Calculations 2. WebChemTutor Ch 7: Electron Shells and Screening 3. WebChemTutor Ch 7: Trends in First and Second Ionization Energy 4. WebChemTutor Ch 7: Periodic Trends 1: Atomic Radius, Electron Affinity, Metallic Character 5. WebChemTutor Ch 7: Periodic Trends 1: Electron Affinity, Metallic Character 6. WebChemTutor Ch 7: Theory of Periodic Trends Chapter 7 Quiz 2 1 The reason why atomic size decreases from left to right in the periodic table is . (A) The number of electrons increases. (B) The effective nuclear charge increases when you go across the periodic table towards the noble gases. (C) The screening experienced by electrons increases. (D) Reactivity increases (E) The effective nuclear charge decreases w ...