structure of atoms part 3

1

AAttoommiic c SSttrruuccttuurree

ParPart 3t 3

2

Recap

3

Recap

• Isotopes:Atoms of the same element having the same number of protons but different number of neutrons

•Hydrogen has three isotopes and chlorine has two isotopes

4

Recap

• The attractive force between the positive charge on the nucleus and the negative charge on the electrons is called electrostatic force

• The way the electrons are arranged is called its electronic structure

5

Recap

2nd shell8 electrons

4th shell8 electrons

Nucleus

3rd shell

8 electrons(proton number 20)

1st shell2 electrons

6

Recap

To find the To find the electronic configurationelectronic configuration of of an atom, we shouldan atom, we should

(1)(1) Fill the electrons into the shell Fill the electrons into the shell nearest to the nucleus first. This shell nearest to the nucleus first. This shell

can take a maximum of 2 electronscan take a maximum of 2 electrons

(2)(2) Once this shell is filled, the Once this shell is filled, the electrons go to the next available electrons go to the next available shell which has a maximum shell which has a maximum capacity of capacity of 8 electrons, and so on.8 electrons, and so on.

7

Overview of topic

Atomic Structure

Structure of Atoms

Isotopes

Electronic Arrangement

Electronic Structure and the Periodic Table

Ions

8

Today’s Menu•Outermost electronsOutermost electrons• Electronic structures and Electronic structures and

The Periodic TableThe Periodic Table• Electrons Structures of Electrons Structures of

Noble GasesNoble Gases• IonsIons

- Positively charged (+) ions- Positively charged (+) ions

- Negatively charged (-) ions- Negatively charged (-) ions

9

What are What are outermost outermost electronselectrons

10

What are outermost What are outermost electronselectrons

Na

The shell furthest The shell furthest away from nucleus away from nucleus is known as the is known as the outermost shelloutermost shell

The electrons on The electrons on the outermost shell the outermost shell are known as the are known as the outermost outermost electronselectrons

Outermost Outermost electrons are also electrons are also known as known as valence valence electronselectrons

11

What are outermost What are outermost electronselectrons

Na

• The outermost The outermost electrons electrons take parttake part in chemical in chemical reactionsreactions

• The inner-shell The inner-shell electrons electrons do notdo not take part in take part in chemical reactionchemical reaction

12

What are outermost What are outermost electronselectrons

ExampleExample

ElementElement Electronic Electronic ConfiguratiConfigurati

onon

No. of No. of outermosoutermos

t et e-- (Valency)(Valency)

No. of eNo. of e-- taking taking part in part in

chemical chemical reactionsreactions

AluminiAluminiumum

2, 8, 32, 8, 3

CarbonCarbon 2, 42, 4

OxygenOxygen 2, 62, 6

44

66

33

44

66

33

13

Electronic Electronic Structures & The Structures & The

Periodic TablePeriodic Table

14

Electronic Structures & The Periodic Electronic Structures & The Periodic TableTable

• The Periodic Table is a way of The Periodic Table is a way of arranging elements by arranging elements by their their valencyvalency

• Elements with the Elements with the same same number of outermost electronsnumber of outermost electrons are in the are in the same same GroupGroup

• The vertical set of elements in The vertical set of elements in the Periodic Table is called a the Periodic Table is called a GroupGroup

15

16

Electronic Structures & The Periodic Electronic Structures & The Periodic TableTable

GrouGroupp

ExampExamplele

Electronic Electronic ConfigurationConfiguration

ValencValencyy

II LiLi 2,12,1 11

NaNa 2, 8, 12, 8, 1

IIII BeBe 2, 22, 2 22

MgMg 2, 8, 22, 8, 2

IIIIII BB 2 ,32 ,3 33

AlAl 2, 8, 32, 8, 3

IVIV CC 2, 42, 4 44

SiSi 2, 8, 42, 8, 4

VV NN 2, 52, 5 55

PP 2, 8, 52, 8, 5

17

Electronic Structures & The Periodic Electronic Structures & The Periodic TableTable

GrouGroupp

ExampExamplele

Electronic Electronic ConfigurationConfiguration

ValencValencyy

VIVI OO 66 66

SS 2, 8, 62, 8, 6

VIIVII FF 2, 72, 7 77

ClCl 2, 8, 72, 8, 7

18

Electron Structure of Noble Gases

19

Electron Structure of Noble Electron Structure of Noble GasesGases

• Noble gases are in Group Noble gases are in Group 00• They have They have full full outermost shelloutermost shell

He

Electronic Electronic ConfiguratiConfiguration: 2 on: 2 (duplet)(duplet)

Electronic Electronic ConfiguratiConfiguration: 2, 8 on: 2, 8 (octet)(octet)

Ne Ar

Electronic Electronic ConfigurationConfiguration: 2, 8, 8 : 2, 8, 8 (octet)(octet)

ExampleExamples:s:

20

Electron Structure of Noble Electron Structure of Noble GasesGases

• Noble gases are unreactive = inert gases

• Noble gases are very stable as they have no tendency to combine with other elements

21

22

Practice Time

23

IonsIons

24

Ions

•Atoms form ions by Atoms form ions by losing or losing or gaining electronsgaining electrons to achieve to achieve the stable full shell the stable full shell configuration of a noble gasconfiguration of a noble gas

• Ion is a Ion is a chargedcharged particle particle

25

Ions

• There are 2 types of ion:There are 2 types of ion:

IonIonss

Positively Positively (+) charged (+) charged ionsions

(Cations)(Cations)

Negatively Negatively (-) charged (-) charged ionsions

(Anions)(Anions)

26

Ions

Remember this. . . Remember this. . .

• In an Atom,In an Atom,

No. of = No. of No. of = No. of

• Therefore, an atom is Therefore, an atom is

protonsprotons electronselectrons

electricalelectricallylyneutrneutr

alal

27

Positively Charged Ion

• When electrons are When electrons are lostlost from an from an atom, atom, the atom has the atom has moremore protons protons than than electronselectrons

• There is an overall There is an overall positivepositive charge charge

• Hence, a Hence, a positively charged ionpositively charged ion (cation) (cation) is formed is formed

X – eX – e-- X X++

28

Negatively Charged Ion

• When electrons are When electrons are gainedgained from an from an atom, the atom has atom, the atom has lessless protons protons than than electronselectrons

• There is an overall There is an overall negativenegative charge charge

• Hence, a Hence, a negatively charged ionnegatively charged ion (anion) (anion) is formed is formed

X + eX + e-- X X--

29

Why do atoms lose Why do atoms lose or gain electronsor gain electrons

30

Why do atoms lose or gain Why do atoms lose or gain electronselectrons

Atoms lose or gain electrons Atoms lose or gain electrons so as to achieve the stable so as to achieve the stable full shell configuration of a full shell configuration of a noble gas noble gas

i.e. duplet (2 ei.e. duplet (2 e-- in the in the outermost shell) or octet (8 outermost shell) or octet (8 ee-- in the outermost shell) in the outermost shell)

31

Practice Time

32

SummarSummaryy

33

Summary1)1) Electrons found on the Electrons found on the

outermost shells are outermost shells are known as the outermost known as the outermost electron (Valence electron (Valence electrons) electrons)

2) 2) The outermost electrons The outermost electrons take part in chemical take part in chemical reactionsreactions

34

Summary

• The Periodic Table is a way The Periodic Table is a way of arranging elements by of arranging elements by their valencytheir valency

• Elements with the same Elements with the same number of outermost number of outermost electrons are in the same electrons are in the same GroupGroup

35

Summary• Noble gases are in Group 0Noble gases are in Group 0• They have full outermost shellThey have full outermost shell

He

Electronic Electronic ConfiguratiConfiguration: 2 on: 2 (duplet)(duplet)

Electronic Electronic ConfiguratiConfiguration: 2, 8 on: 2, 8 (octet)(octet)

Ne Ar

Electronic Electronic ConfigurationConfiguration: 2, 8, 8 : 2, 8, 8 (octet)(octet)

ExampleExamples:s:

36

Summary

• Atoms form ions by losing or gaining Atoms form ions by losing or gaining electrons to achieve the stable full electrons to achieve the stable full shell configuration of a noble gasshell configuration of a noble gas

•There are 2 types of ion:There are 2 types of ion:

IonIonss

Positively Positively (+) charged (+) charged ionsions

(Cations)(Cations)

Negatively Negatively (-) charged (-) charged ionsions

(Anions)(Anions)

37

Summary

• Positively charged ion (cation)Positively charged ion (cation)

• Negatively charged ion (anion)Negatively charged ion (anion)

X – eX – e-- X X++

X + eX + e-- X X--

38

Summary

• Atoms lose or gain electrons so Atoms lose or gain electrons so as to achieve the stable full as to achieve the stable full shell configuration of a noble shell configuration of a noble gas gas

i.e. duplet (2 e- in the i.e. duplet (2 e- in the outermost shell) or octet (8 e- outermost shell) or octet (8 e- in the outermost shell)in the outermost shell)

39

Any Any QuestionsQuestions