PERIODICITY (TOPICS 3 AND 13) IB Chemistry HL2

Review: Periodic table, Physical and Chemical Properties of elements (Topic 3) Describe the arrangement of elements in the periodic table in order of increasing atomic number ( A.3) Distinguish between the terms group and period ( A.3) Apply the relationship between the electron arrangement of elements and their position in the periodic table up to element n=20 ( A.3) Apply the relationship between the number of electrons in the highest occupied energy level for an element and its position on the periodic table ( A.3) Define the terms first ionization energy and electronegativity. Describe and explain the trends in atomic radii, ionic radii, first ionization energy, electronegativity, and melting points for alkali metals and the halogens. Describe and explain the trends in atomic radii, ionic radii, first ionization energies, and electronegativity for elements across period 3 ( A.3) Compare the relative electronegativity of two or more elements based on their positions in the periodic table. Discuss the similarities and differences in the chemical properties of elements in the same group Discuss the changes in nature, from ionic to covalent and from basic to acidic, of the oxides across Period 3.

3 IB note: Inner transition elements are of little interest at this level

4 Trends in Atomic Radii

5 Comparison of Atomic Radii with Ionic Radii

6 Cation is always smaller than atom from which it is formed. Anion is always larger than atom from which it is formed.

7 Ionization energy is the minimum energy (kJ/mol) required to remove an electron from a gaseous atom in its ground state. I 1 + X (g) X + (g) + e - I 2 + X + (g) X 2 + (g) + e - I 3 + X 2+ (g) X 3 + (g) + e - I 1 first ionization energy I 2 second ionization energy I 3 third ionization energy I 1 < I 2 < I 3

8 General Trends in First Ionization Energies Increasing First Ionization Energy

9 Electron affinity is the negative of the energy change that occurs when an electron is accepted by an atom in the gaseous state to form an anion. X (g) + e - X - (g) F (g) + e - F - (g) O (g) + e - O - (g)  H = -328 kJ/mol EA = +328 kJ/mol  H = -141 kJ/mol EA = +141 kJ/mol

10 The metals in these two groups have similar outer electron configurations, with one electron in the outermost s orbital. Chemical properties are quite different due to difference in the ionization energy. Comparison of Group 1A and 1B Lower I 1, more reactive

11 Properties of Oxides Across a Period basicacidic

Do NOW Classify the following oxides as acidic, basic, or amphoteric: (a) Na 2 O (b) P 4 O 10 (c) SO 2

Objectives (Topic 13) Trends Across Period 3  Explain the physical states (under standard conditions) and electrical conductivity (in the molten state) of the chlorides and oxides of the elements in period 3 in terms of their bonding and structure.   Describe the reactions of chlorine and the chlorides with water 

Explain why Scandium and Zinc are not considered to be transition elements. Sc and Zn do not form colored solutions; due to electronic configuration of their ions and the lack of partially filled d orbital Explain the existence of variable oxidation number in ions of transition elements First-row d-block elements List the characteristic properties of transition elements

15 Electron Configurations of Cations of Transition Metals When a cation is formed from an atom of a transition metal, electrons are always removed first from the ns orbital and then from the (n – 1)d orbitals. Fe: [Ar]4s 2 3d 6 Fe 2+ : [Ar]4s 0 3d 6 or [Ar]3d 6 Fe 3+ : [Ar]4s 0 3d 5 or [Ar]3d 5 Mn: [Ar]4s 2 3d 5 Mn 2+ : [Ar]4s 0 3d 5 or [Ar]3d 5

Define the term ligand. Ligands are a species (atom or ion) that can donate an electron pair to a central transition metal atom/ion to form a dative covalent bond. Common ligands include H2O, CN-, OH- NH3 Cl-. Ligands must have a lone pair but they do not have to be negative - they can be neutral, but never positive Describe and explain the formation of complexes of d- block elements.

Explain why some complexes of d-block elements are colored State examples of the catalytic action of transition elements and compounds Outline the economic significance of catalysts in the Contact and Haber processes. Iron (Fe) in the Haber process: manufacture of ammonia- the raw material for fertilizers, plastics, drugs, etc. V 2 O 5 in the Contact process: SO 2 + O 2  SO 3 – for the manufacture of sulfuric acid, the world’s most important chemical.

18 Compounds of the Noble Gases A number of xenon compounds XeF 4, XeO 3, XeO 4, XeOF 4 exist. A few krypton compounds (KrF 2, for example) have been prepared.

19 Chemistry in Action: Discovery of the Noble Gases Sir William Ramsay