Chapter: 3 PeriodicityTitle: 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

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Reflecting on the Periodic Table

What is the periodic table and what is supposed to show?

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The TraditionalBased on Mendeleev’s work. Easiest to use and display.

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Dmitri Mendeleev’s Periodic TableThe one that started it all off.

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Wide Format Periodic TableShows true position of the f-block (lanthanides and actinides)

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Janet Periodic TableElements arranged in order of orbital filling. Used frequently by physicists.

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Benfey Periodic TableSpiral form shows the steady increase in atomic number.

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The Structure of the Periodic Table

PERIODS

GR

OU

PS

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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

Gro

up

1 G

rou

p

2 Gro

up

3 G

rou

p

4 Gro

up

5 G

rou

p

6 Gro

up

7 G

rou

p

0

Transition Elements

s-b

lock

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

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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

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Key Points

The periodic table arranges the elements according to:

Their chemical properties

Their electronic structure

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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.

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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.

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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.

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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?

3s23p4 (six valence electrons)

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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 table