Type of Forces 1 Notes 2010

8/8/2019 Type of Forces 1 Notes 2010

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1

TYPE OF FORCES IN SUBTANCES

SUBSTANCE

ELEMENT COMPOUND

ATOM MOLECULE MOLECULE ION

O O OH H

OH HO O

+ -

Na Cl

Nuclei attraction

between proton in

the nucleus to the

electrons in the

shells

Weak Van der

Waals forces

between

moleculesStrong electrostatic

forces in between

positive and negative

ions

Strong covalent bond

between atom in the

molecule



2

Types of

forces

Types of

substanceDescription Application

Van der

Waals

Covalent

compoundWeak forces

between

molecules.

Become stronger

when the size of the molecules

increases

Explain the low melting and

boiling points of covalent

compound.

Explain the change of state

of matter in Group 17 and

the change in the meltingand boiling points of Group

17 and Group 18

Explain the change in the

physical properties for the

members of homologus

series

Electrostatic Ionic

compoundStrong forces

between ions.

Explain high melting point

of ionic compound



3

Types of

forces

Types of

substanceDescription

Nucleiattraction

(force of

attraction

between

nucleus and

valence

electron/s)

In the atom / molecule

of an

element

Across PeriodAs the proton

number increases,

the positive charge in

the nucleus

increases.

The force of

attraction betweennucleus and

electrons in the

shells becomes

stronger

The atomic size

becomes smaller

It is easier for theatom to gain electron,

the atom become

more electronegative

Group 1Going down the

group:

Proton number

increases

Number of shells

that are occupied by

electron increases:

Atomic size

increases

The strength of

nuclei attraction

between nucleus

and valence

electron/s decreases

Easier for the atom

to release electron

(more

electropositive)

Group 17Going down the

group

Proton number

increases

Number of shells

that are occupied by

electron increases:

Atomic size

increases

The strength of

nuclei attraction

between nucleus and

valence electron/s

decreases

Tendency to

receive electron

decreases(less

electronegative)



4

Nuclei Attraction In an Atom

Nuclei attraction

between proton in the

nucleus to theelectrons in the shells

Na



5

Element in Period 3

ELEMENT

Na Mg Al Si N S Cl Ar

PROTON

NUMBER 11 12 13 14 15 16 17 18

ELECTRON

ARRANGEMENT 2.8.1 2.8.2 2.8.3 2.8.4 2.8.5 2.8.6 2.8.7 2.8.8



6

Na Mg Al Si P S

Change In Atomic Size Across Period Three

11p

(11+)

2.8.1

12p(12+)2.8.2

13p

(13+)

2.8.3

14p

(14+)

2.8.4

15p

(15+)

2.8.5

16p

(16+)

2.8.6

The atomic size decreases across Period 3

All atoms of element across period have 3 shells occupy with electrons

The positive charge in the nucleus increases

The nuclei attraction to the electrons in the shells increases

Cl

17p

(17+)

2.8.7



7

Change in reac tivity down the Group 1

Li

Na

K

All atoms of element in Group 1 have «.. valence

electrons achieve a stable octet electron arrangement

by releasing ««. electron to form «««« charge ion, X+

The atomic size ««««« going down the group

because of increase in number of «««..

The valence electron in the outermost shell «««..

away from the nucleus.

The nuclei attraction to the valence electron gets ««««,

the valence electron is loosely held and it is «««« for

the electron to be released.

The reactivity of element Group 1 increases down the group



8

Change in reac tivity down the Group 17

F

Cl

Br

All atoms of element in Group 17 have «.. valence

electrons achieve a stable octet electron arrangement

by accepting ««. electron to form «««« charge ion.

The atomic size ««««« going down the group

because of increase in number of «««..

The valence electron in the outermost shell «««..

away from the nucleus. The nuclei attraction to the electrons

in the shells gets ««««,

The strength of a halogen atom to attract electron «««..

from flourine to iodine



9

F

Cl

Br

Na Mg Al Si P S Cl

Li

Na

K

COMPARING ATOMIC SIZE / ELECTRONEGATIVITY ACROSS PERIOD

COMPARING CHANGE IN REACTIVITY DOWN GROUP 1/ 17

Compare number of shells in each atom

Compare number of proton in the nucleus

Compare the strength of nuclei attraction to the

electrons in the shells

Compare number of shells in each atom

Compare the strength of nuclei attraction tothe valence electron (Group 1)// to attract

electron to the outermost shells (Group 17)

Compare tendency of the atom to release/

receive electron



10

Comparing Atomic Size /

Electronegativity Across Period

Compare number of protons in the

nucleus

Write electron arrangement /Compare

number of shells

Compare the strength of nuclei attraction

between protons in the nucleus to theelectrons in the shells

Compare atomic size

Compare tendency to receive electrons

Comparing Change In Reactivity

Down Group 1/ Group 17

Compare number of shells

Compare the strength of nuclei attraction

between proton in the nucleus to the

electrons in the shells

Compare tendency to receive /

release electrons



11

1. The diagram below shows the electron arrangement of atom X and atom Y fromGroup 1 in the Periodic Table of Elements.

Compare the reactivity of atom X and atom Y.

Explain your answer by referring to attractive forces between the nucleus and the valence

electrons. [6 marks]

X Y



12

Electron

arrangemen

t in atom X

and Y

Compare

number of

shells

Compare

atomic size

Compare

the strength

of nuclei

attraction

Compare

tendency to

release

electron

Compare

reactivity

Atom X Atom Y



13

P1 & P2 Atom Y is more reactive than atom X.

P 3 & P4 The atomic size Y / the size of atom Y is greater than atom X. //The valence

electron of atom Y is further away from the nucleus compare to atom X.

P5 & P6 The attraction forces between nucleus and valence electron of atom Y is weaker

than atom X.

//it is easier for atom Y to donate / release / lose the valence electron compare to

atom X.

Or

P1 Atom Y is more reactive.P2 The valence electron of atom Y is further away from the nucleus

// Atom Y has bigger atomic size.

P3 The attraction forces between nucleus and valence electron of atom Y is weak.

P4 Atom X is less reactive.

P5 The valence electron of atom X is closer to the nucleus //Atom XY has smaller atomicsize.

P6 The attraction forces between nucleus and valence electron of atom X is strong.



14

2. The table below shows the proton number of a few elements.

Element Proton Number

R 1

S 11

T 14

W 18

X 19

(a) Write the electron arrangement of atom W

[ 1 mark]

(b) Give a reason why W is not reactive[ 1 mark]

(c) Elements S and T are located in the same period

(i) State the element with a bigger atomic size.

[ 1 mark](ii) Explain your answer in (c)(i)

[ 3 marks]



15

Element S T

Proton number 11 14

Electron

arrangement in

atom S and T

Compare number

number of shells

Compare number

of proton in the

nucleus

Compare the

strength of nuclei

attraction

Compare atomic

size

2.8.1 2.8.4





17

Element S X

Proton number 11 19

Electron

arrangement in

atom S and T

Compare number

number of shells

Compare the

strength of

nuclei attraction

Compare

tendency torelease electrons

Compare

reactivity

2.8.12.8.8.1



18

VAN DER WAALS FORCES BETWEEN MOLECULES



19

Van Der Waals For ce Between Molecules

Cl Cl

Cl Cl

Weak Van der Waals

forces between molecule

Br Br

Br Br I I

I I

Strong Van der Waals

forces between molecule

Strongest Van der Waals forces between

molecule

Gas LiquidSolid



20

ELECTROSTATIC FORCES BETWEEN IONS



21

X ± X ± X ± X ±M+

X ±

X ±

X ±X ±

X ±

X ±

X ±

X ±

X ±

M+ M+ M+

M+ M+M+ M+

M+M+M+M+

M+M+M+M+

X ±X ±

X ± X ±X ±

X ±X ±M+M+M+M+

Strong electrostatic forces between positive and negative ions

Electrostatic Forces Between Positive And Negative Ions



22

Cl Cl

-

ClCHLORINE ATOM

CHLORINE MOLECULE, Cl2

CHLORIDE ION, Cl-

ClCl



23

3. Diagram shows the chemical symbols which represent elements X, Y and Z.

23

11

X 16

8

Y12

6

Z

(b)Atoms of X and Y can react to form a compound.

(i)Name the type of bond in the compound formed between atoms X and Y

[1 mark ]

(ii)Draw the electron arrangement for the compound formed. [2 marks]

+

X

2-

Y

+

X



24

(c) Atoms of Y and Z can also react to form a compound. Draw the electron

arrangement for the compound formed.

[ 2 marks]

(d)Compare one physical property of compound formed (b) and (c). Explain your

answer.

[4 marks]

Z YY





26

Electron

arrangement

in the

compound

Compound A Compound B

Compare type

of particles

Compare

electrical

conductivity

Explanation

+

X

2-

Y

+

X Z YY

Type of Forces 1 Notes 2010

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