Chapter: 3 Periodicity Title: Lesson 1 The Periodic Table Learning Objectives: Reflect on prior knowledge of the periodic table Understand the structure and purpose of the periodic table Repeat the work of Mendeleev by constructing your own periodic table

Main Menu Reflecting on the Periodic Table  What is the periodic table and what is supposed to show?

Main Menu The Traditional Based on Mendeleev’s work. Easiest to use and display.

Main Menu Dmitri Mendeleev’s Periodic Table The one that started it all off.

Main Menu Wide Format Periodic Table Shows true position of the f-block (lanthanides and actinides)

Main Menu Janet Periodic Table Elements arranged in order of orbital filling. Used frequently by physicists.

Main Menu Benfey Periodic Table Spiral form shows the steady increase in atomic number.

Main Menu The Structure of the Periodic Table PERIODS GROUPS

Main Menu The periodic table and electron configuration  How does an element’s position in the PT relate to its electron configuration?

THE MODERN PERIODIC TABLE occur in the same vertical columns (GROUPS). = the elements arranged in rows (PERIODS) such that chemically similar elements in order of increasing atomic number (Z)

Period 1 Period 2 Period 3 Period 4 Period 5 Period 6 Period 7 Group 1 Group 2 Group 3Group 4Group 5Group 6 Group 7 Group 0 Transition Elements

s-block d-block p-block

Group VII GROUP Group number = number of electrons in highest occupied energy level e.g. Group I the alkali metals the halogens eg Na[2,8,1] = eg F[2,7] = = elements within the same vertical column Chemical and physical properties are similar within a group

PERIOD Chemical and physical properties change from extremes across any period. e.g. Period 3 Sodium = a reactive metallic solid Argon = an unreactive, non- metallic gas eg Si (Z=14) Period number = number of energy levels  2,8,4  Period 3 and Group 4 = elements within the same horizontal row

Main Menu Groups and Periods - Summary  Groups  Elements show similar chemical properties  Elements show similar trends in their chemical properties  Periods  As you move across periods, changes in the chemical and physical properties that are repeated in the next period  This is what ‘period’ and ‘periodic’ refers to

Main Menu Key Points  The periodic table arranges the elements according to:  Their chemical properties  Their electronic structure

Main Menu Elements whose valence electrons that occupy an s sub level make up the s block. The same can be said with p block, d block and f block elements. E.g. Sodium: Period 3 (3 principal energy levels) Group 1 (one electron in the valence energy level {Ne} 3s1.

Main Menu Metals and Non Metals  Metals, non metals and metalloids occupy different regions of the PT.  Metalloids have the characteristics of both metals and non- metals.  The physical properties and appearance most resemble the metals, although chemically they are more like non metals.

Main Menu Metallic properties  A metallic structure consists of a regular lattice of positive ions and a sea of delocalised electrons.  To form metallic structure, an element must be able to lose electrons to form positive ions.  Going across a period means an increase of ionisation energy (thus less easy to lose electrons)  Metallic structures are formed by elements on the left hand side because of the lower ionisation energy.

Main Menu The periodic table and electron configurations  Electrons in the outer shell are called valence electrons.  The group number is related to the number of valence electrons.  For elements in groups 13-18, the number of valence electrons is given by: GROUP NUMBER – 10  Periodic table divided into s, p, d and f blocks. E.g. Sulphur: Period 3, group 16, p block. So we know… 3 shells, (16-10) valence electrons, highest energy shell is a p sub shell.  What is the outer shell electron configuration? 3s 2 3p 4 (six valence electrons)

Main Menu Being Mendeleev  The first widely accepted periodic table was produced by the Russian chemist Dmitri Mendeleev  It was a tremendous example of scientists as risk-takers as it was able to make a number of predictions thought unlikely at the time  Complete the exercise here in which you will use the information available to Mendeleev to construct your own periodic tablehere