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UNIT 3: PERIODIC TABLE

HISTORICAL DEVELOPMENT- To identify the contribution of scientists in the arrangement of elements in the Periodic

Table.- To get ideas on the arrangement of elements in the Periodic Table based on their proton

numbers.

ARRANGEMENT OF ELEMENT IN THE PERIODIC TABLEGROUP - To write the electron arrangement for atoms of elements with proton numbers 1 to 20.

PERIOD - To determine the group and period based on the electron arrangement of atoms or

otherwise.

PROPERTIES OF ELEMENTS IN THE PERIODIC TABLEGROUP 18- To explain the existence of noble gases as monoatoms and their uses.

GROUP 1 - To explain physical properties, similar chemical properties (with water, oxygen and

chlorine) and the different reactivities.

GROUP 17 - To explain physical properties, similar chemical properties (with water, sodium hydroxide

and iron) and the different reactivities.

PERIOD 3 - To explain changes in atomic size, electronegativity, metallic properties as well as oxide

properties across period 3 from left to right.

TRANSITION ELEMENTS

-

To state metallic properties of transition metals and their special characteristics.



Advantages of Classifying the Elements in the Periodic Table

1. Elements are arranged systematically in the Periodic Table in an increasing order of proton number which enables:a. chemists to study , understand and remember the chemical and physical properties

of all the elements and compounds in an orderly manner,b. properties of elements and their compounds to be predicted based on the position

of elements in the Periodic Table,c. relationship between elements from different groups to be known.

Contribution of Scientist to the Historical Development of the Periodic Table

Scientists Discoveries

Antoine -

Substances were classified into 4 groups with similar chemical properties. J.W

Dobereiner - Substances were arranged in 3 groups.- Groups with similar chemical properties were called Triads.- Triad system was confined to some elements only.

JohnNewlands

- Elements were arranged in accending atomic mass.- Law of Octaves because similar chemical properties were repeated at every

eighth element.- This system was inaccurate because there were some elements with wrong mass

numbers.Lothar

Meyer

- The atomic volume = ( )

( )

- Plotted graph for the atomic volume against atomic mass.- Found that elements with similiar chemical properties were positioned at

equivalent places along the curve.Mendeleev - Elements were arranged in ascending order of increasing atomic mass.

- Elements with similar chemical properties were in the same group.- Empty spaces were allocated for elements yet to be discovered.- Contributor to the formation of the modern Periodic Table.

HenryMoseley

- Classified concepts of proton number and elements in accending order of increasing proton number.

- Contributor to the formation of the modern Periodic Table.



1. Write the electron arrangement for each atom of element in the Periodic Table below.

2. Elements in the Periodic Table are arranged horizontally in increasing order of protonnumber .

3. Two main components of the Periodic Table:

i. Groupii. Period

Period

a. The vertical column of elements in the Periodic Table arranged according to thenumber of valance electron in the outermost shell of atoms is called groups.

b. There are 18 vertical columns, called Group 1, Group 2, and Group 3 until Group 18.

Number of Valence Electrons 1 2 3 4 5 6 7 8(except Helium)

Group 1 2 13 14 15 16 17 18

For atoms of elements with 3 to 8 valence electrons,the group number is: 10 + number of valence electrons.



c. Specific name of groups: Group 1 – Alkali metals # Group 2 – Alkali-earth metals. Group 3 to 12 – Transition elements #

Group 17 – Halogens # Group 18 – Noble gases #

# The important groups that will be studied with respect to chemical andphysical properties.

d. Types of substances according to the groups:- Elements of group 1, 2 and 13 – atoms of each element have 1, 2 and 3 valence

electrons respectively are metals.- The elements of group 3 to 12 – transition

elements are metals.- The elements of Group 14, 15, 16, 17 and 18

– atoms of each element have 4, 5, 6 7 and 8valence electrons respectively are non-metals.

Period

1. The horizontal row of elements in the Periodic Table, consists of the same number of shells occupied with electrons in an atom are called period.

2. There are seven horizontal rows of elements known as period 1, 2, ....., 7 [Refer to theperiodic table] a) Period 1 – has 2 elements b) Period 2 and 3 # – have 8 elements c) Period 4 and 5 – have 18 elements d) Period 6 – has 32 elements e) Period 7 – has 23 elements

Short periods, # Period 3 will be studied in detailwith respect to physical and chemical properties

Long periods



EXERCISE

1. Complete the table below.

Element ProtonNumber

ElectronArrangement in

atom

Number of Valence

Electrons inatom

Group Number of Shell in atom

Period

H 1 1 1 1 1 1He 2 2 2 18 1 1Li 3 2.1 1 1 2 2Be 4 2.2 2 2 2 2B 5 2.3 3 13 2 2C 6 2.4 5 15 2 2

N 7 2.5 6 16 2 2O 8 2.6 7 17 2 2F 9 2.7 8 18 2 2

Ne 10 2.8 1 1 3 3Na 11 2.8.1 2 2 3 3Mg 12 2.8.2 3 2 3 3A1 13 2.8.3 3 3 3 3

EXERCISE

1. The diagram below shows the chemical symbols which represent elements X, Y andZ.

a. The proton number of element X is 11 and the number of proton inatom X is 11 . The number of electrons in atom X is 11 . The electronarrangement of atom X is 2.8.1 . Element X is located in Group 1 becauseatom X has one valence electron . It is Period 3 because atom X has three shells occupied /filled with electrons .

b. i. State the position of element Y in the Periodic Table. Element Y is located in Group 14 and Period 2

2 66 9

9



ii. Explain how you determine the position of element Y in the PeriodicTable.- The proton number of element Y is 6 and the number of proton in

atom Y is 6.

- The electron arrangement of atom Y is 2.4.- Element Y is located in Group 14 because atom Y has 4 valanceelectron.

- It is in Period 2 because atom Y has 2 shells occupied/filled withelectrons.

c. Which of the above elements show the same chemical properties? Explainyour answer.

- Element X and element Z.- Electron arrangement of atom X is 2.8.1 and electron arrangement of

atom Z is 2.8.8.1- Atom X and atom Z have the same number of valence electron.

Group 18 (Noble Gases)

1. Consist of Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe) andRadon (Rn).

Elements Electron arrangement Helium 2 Neon 2.8 Argon 2.8.8

Krypton 2.8.18.8

2. They are chemically inert because the outermost shell of the atom has achieved dupletelectron arrangement for helium and octet electron arrangement for others.

3. It does not combine with other elements (does not lose, gain or share electrons).4. These gases exist as single uncombined atoms and are said to be monoatomic gases.5. Going down group 18:

a. The atomic size is increasing because the number of shells increases.b. The melting point/boiling point is very low because atoms of noble gases atoms

are attracted by weak Van der Waals forces, less energy is required to overcomethese forces. However, the melting / boiling point increases going down the groupbecause atomic size increases, causing the Van der Waal forces to increase andmore energy is required to overcome these forces.

c. The density is low and increases gradually because the mass increases greatlygoing down the group.

6. All noble gases are insoluble in water and cannot conduct electricity in all conditions.



7. Complete the uses of noble gases in the table below:

Noble gases UsesHelium To fill weather balloons and airship Neon To fill neon light (for advertisement board) Argon To fill electrical bulb

Krypton To fill photographic flash lamp Radon To treat cancer

Group 1 (Alkali Metals)

1. Consist of Lithium(Li), Sodium(Na), Potassium(K), Rubidium(Rb), Cesium(Cs) andFrancium(Fr).

Elements Symbol Proton Number Electron Arrangementin atom

Number of Shellsin atom

Lithium Li 3 2.1 2Sodium Na 11 2.8.1 3

Potassium K 19 2.8.8.1 4

2. Physical properties:a. Grey solid with shiny surface.b. Softer and the density is lower compared to other metals.c. Lower melting and boiling points compared to other metals.

3. Changes in physical properties going down the group:a. Atomic size increases because the number of shells increases.b. Density increases because mass increases faster than the increase in radius.c. Melting and boiling point decreases because when the atomic size increases, the

metal bonds are weaker.

4. Chemical Properties of Group 1 elements:

a. Each atom has one valence electron; the stable octet electron arrangement isachieved by releasing one valence electron.

b. All elements in Group 1 have similar chemical properties because all atoms inGroup 1 have one valence electron and achieve the stable electron arrangementby releasing its valence electron to form a positive charged ion.



c. The reactivity of alkali metals increases going down the group.Explanation:

i. Atoms of Group 1 metals achieve a stable electron arrangement of noblegases by releasing one valence electron to form +1 charged ion.

ii.

The reactivity of Group 1 metals depends on the ability for atoms to loseelectrons; the easier it is to lose an electron, the greater the reactivity of the metal.

iii. Going down Group 1, the number of shells increases, the atomic radiusincreases and the valence electron in the outer most shell gets further away from the nucleus. The nuclei attraction on the valence electron getsweaker , the valence electron is loosely held and it is easier for theelectron to be released.

5. Chemical Reactions of Group 1 elements:a. With water

2X + 2H 2O → 2XOH + H 2, X is a metal element of Group 1

Element Observation Chemical equation Li Lithium moves slowly on the water surface. The

colourless solution formed turns red litmus to blue.2Li + H 2O → 2LiOH + H 2

Na Sodium moves quickly on the water surface and produces yellow flame. The colourless solution formed turns red litmus to blue.

2Na + H 2O → 2NaOH + H 2

K Potasium moves very quickly on the water surfaceand produce yellow flame. The colourless solution

formed turns red litmus to blue.

2K + H 2O → 2KOH + H 2

b. With chlorine gas:

2X + Cl 2 → 2XCl, X is a metal element of Group 1



Element Observation Chemical equation Li Lithium burns slowly with a red flame.

A white solid is produced.2Li + Cl 2 → 2LiCl

Na Sodium burns brightly with a yellow flame. A white solid is produced.

2Na + Cl 2 → 2NaCl

K Potassium burns very brightly with a purple flame. A white solid is produced.

2K + Cl 2 → 2KCl

c. With oxygen gas: (**the set-up of apparatus is similar to the reaction withchlorine gas.)

Element Observation Chemical equationLi Lithium burns slowly with a red flame.

A white solid is produced.

4Li + O 2 → 2Li 2O

Li2O + H 2O → 2LiOH Na Sodium burns brightly with a yellow flame. A white solid is produced.

4Na + O 2 → 2Na 2ONa 2O + H 2O → 2NaOH

K Potassium burns very brightly with a purple flame. A white solid is produced.

4K + O 2 → 2K 2OK2O + H 2O → 2KOH

Conclusion: Going down Group 1: Li Na K Rb Increase in reactivity

EXERCISE

1. The diagram below shows the electron arrangement for atoms P and Q.

a. i. Element P and Q are placed in the same group in Periodic Table. State the

group.- Group 1

ii. How is element P and Q kept in the laboratory? Give reason for youranswer.

- In paraffin oil - To prevent them from reacting with oxygen or water vapour in the

atmosphere.



b. State one difference in physical properties between element X and element Y.

Melting point of element Q is lower than element P// Density of element Q ishigher than P// atomic size of Q is bigger than P

c. i. Write chemical equation for the reaction between elements P with water.

2P + 2H 2O → 2POH + H 2

ii. What is the expected change of colour when a few drops of phenolphthaleinare added into the aqueous solution of the product? Explain your answer.

- Colourless to purple/ pink - The solution formed is alkaline

iii. Between element P and element Q, which is more reactive in the reactionwith water. Explain your answer.

- Element Q is more reactive than P - The size of atom Q is greater than atom P - The valence electron of atom Q is further away from the nucleus

compared to atom P. - The attraction forces between nucleus and valence electron of atom Q

is weaker than atom P - Atom Q is easier to release the valence electron compared to atom P

d. Name one element that has the same chemical properties as P and QPotassium

Group 17 (Halogens)

1. Consist of Fluorine (F 2), Chlorine (Cl 2), Bromine (Br 2), Iodine (I 2) and Astatine (At 2)

Elements Symbol Proton Number Electron Arrangementin atom

Number of Shellsin atom

Fluorine F2 9 2.7 2Chlorine Cl 2 17 2.8.7 3Bromine Br 2 35 2.8.18.7 4

Iodine I 2 53 2.8.18.18.7 5

2. Physical Propertiesa. Does not conduct electricity in all state.b. Does not conduct heat.



3. Changes in physical properties going down the group :-a. Physical properties change from gas (Fluorine and Chlorine) to liquid

(Bromine) and to solid (Iodine) at room temperature.b. The atomic size increases going down the group because of increase in

number of shell . c. The density is low and increases going down the group.d. The melting and boiling points are low because the molecules are attracted by

weak Van der Waals forces, and small amount of energy is required toovercome these forces. However the melting/boiling point increases goingdown the group because the increase in atomic size causes a stronger molecular forces. More energy required to overcome this forces .

e. The colour of the elements becomes darker going down the group: Fluorine(light yellow), Chlorine (greenish yellow), Bromine (Brown) and Iodine(Purplish black).

4. Chemical properties of Group 17 elementsa. All atoms of elements in Group 17 have 7 valence electron and achive a stable

octet electron arrangement by accepting one electron to form negative chargedions:

b. Chemical properties of all elements are similar because the number of valenceelectrons in atoms are the same and achieve the stable octet electronarrangement in a similar way.

c. Reactivity of halogens decreases going down the group :Explanation:

i. All the atoms of Group 17 have seven valence electrons and achieve astable octet electron arrangement by accepting one electron to form – 1charged ion or by sharing a pair of electrons.

ii. The reactivity of a halogen atom depends on the tendency of the atomto accept electron.

iii. Going down Group 17, the number of shells increases, atomic size increases.

iv. Outer shell becomes further from the nucleus.v. The strength to attract one electron into the outer most occupied shell

by the nucleus becomes weaker .vi. The strength of a halogen atom to attract electron decreases from

fluorine to astatine (electronegativity decreases)



vii. Exist as diatomic molecules (2 atoms of elements sharing a pair of valence electrons) to achieve stable octet electron arrangement.(Complete the electron arrangement for the atom and molecule below)

The elements of the group exist as diatomic molecules: F 2, Cl 2,Br2, I2 and At 2

5. Chemical reactions of Group 17 elements:a. With water

i. Solubility (The reactivity of reaction decreases going down Group 17)

ii. Reaction with bromine - shake bromine with water, a brown solution isformed

Br2 + H 2O HBr + HOBriii. Reaction with iodine:

I2+ H 2O HI + HOI

b. With Sodium hydroxide, (NaOH):X2+ 2NaOH → NaX + NaOX + H 2O

I2+ 2NaOH → NaI + NaOI + H 2O

c. With iron (Fe):

2Fe + X 2 → 2FeX 3, X 2 represents any halogen (Cl 2, Br 2 or I 2)





c. i. Element X can react with sodium hydroxide solution. Write the chemicalequation for the reaction.

X2 + 2NaOH → NaX + NaOX + H 2O

ii. Between elements X and Y, which is more electronegative? X is more electronegative than element Y

iii. How does the reactivity of element X and element Y differ? Explain youranswer.- Element X is more reactive than element Y - The size of atom X is smaller than atom Y - The outermost occupied shell of atom X is nearer to the nucleus

compare to atom Y. - The strength of the nucleus of atom X to attract electron into the

outermost shell is stronger than atom Y

Period1. Horizontal rows in the periodic table2. There are seven periods known as period 1, 2, 3, 4, 5, 6, 7.3. The number of period of an element represents the number of shells occupy with

electrons in each atom of element.Elements Proton

NumberElectron Arrangement in

atomNumber of shells in

atomPeriod

Li 3 2.1 2 2 Na 11 2.8.1 3 3 K 19 2.8.8.1 4 4

4. Period 3 elementsElements Na Mg Al Si P S Cl Ar

Proton Number 11 12 13 14 15 16 17 18Electron 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 Positive charge in the nucleus +11 +12 +13 +14 +15 +16 +17 +18Radius 0.156 0.136 0.125 0.117 0.110 0.104 0.009 0.001

5. Physical changes across the period 3 (from left to right) a. Atomic radius decreases because:

i. All the atoms of elements have 3 shells occupied with electrons.ii. The proton number increases by one unit from one element to the next

element.iii. Increase in proton number causes the number of positive charge in the

nucleus to increase .iv. The strength of nuclei attraction on the electrons in the shells

increases .v. The atomic radius of elements decreases .



b. Electronegativity increases:i. Electronegativity: The strength of an atom in a molecule to attract

electron towards its nucleus.ii. The atomic radius decreases due to the increasing nuclei attraction on

the valence electron.iii. The strength of nucleus to attract electrons also increases .

c. Physical state:i. The physical state of elements in a period changes from solid to gas

from left to right.ii. Metals on the left are solid while non-metals on the right are usually

gases.

d. Changes in metallic properties and electrical conductivity:

Element Na Mg Al Si P S Cl ArMetallic

propertiesMetal Semi metal Non metal

Electricalconductivity

Good conductorsof electric.

Weak conductor of electricbut it increases with thepresence of boron orphosphorous.Uses: semi-conductor

Cannot conductelectricity

6. Properties of oxide of elements in Period 3:a. Elements in Period 3 can be classified as metals and non-metals based on

basic and acidic properties of their oxides.

Na Mg Al Si P S Cl

Basic oxide Amphoteric oxide Acidic oxide

Metal oxide + water → alkali

Example:Na 2O + H 2O → 2NaOH

Metal oxide + Acid → Salt +

WaterExample:MgO + 2HCl → MgCl 2 + H 2O

Amphoteric oxide react with both acid

and alkali to produce + salt and waterExample:Al2O3 + 6HNO 3 → 2Al(NO 3)3 +3H 2OAl2O3 + 2NaOH → 2NaAlO 2 + H 2O

Non metal oxide + water → acid

Example:SO 2 + H 2O → H 2SO 3

Non metal oxide+ alkali → Salt + WaterExample:SiO 2 + 2NaOH → N 2SiO 3 + H 2O



b. i. Basic oxide is metal oxide that can react with acid to form salt and water .ii. Acidic oxide is non-metal oxide that can react with alkali to form salt and

water iii. Amphoteric oxide is oxide that can react with both acid and alkali to form

salt and water .

c. Complete the following table:i. Reaction with water:

Oxide Solubility in Water pH of theSolution

Type of Oxide

Sodium oxide,Na 2O

White solid dissolve inwater

14 Basicoxide

Magnesium oxide,MgO

White solid slightlydissolve in water

9 Basicoxide

Aluminium oxide,Al 2O3

Insoluble - -

Silicon oxide, SiO 2 Insoluble - -Phosphorousoxide, P 4O10


3 Acidicoxide

Sulphur dioxide,SO 2


3 Acidicoxide

ii. Reaction between nitric acid and sodium hydroxide solution:

Oxide Observation

Type of Oxide

Reaction withDilute Nitric Acid

Reaction withSodium Hydroxide

SolutionMagnesiumoxide, MgO

The white soliddissolve to formcolourless solution

No change. Thewhite solid does notdissolve

Basic oxide

Aluminiumoxide, Al 2O3



Amphotericoxide

Silicon oxide,SiO 2

No change. Thewhite solid does notdissolve


Acidicoxide



Transition Element

1. Situated between Group 2 and 13. The example of transition element are Sc, Ti, V,Cr, Mn, Fe ,Co , Ni, Cu, and Zn.

2.

Show metal properties:- Shiny, conducts heat and electricity, malleable, high tensil strength, highmelting point and density.

3. Special characteristics:a. Form coloured compound

Example: Iron (III) chloride is brown, Iron (II) chloride is green and copper(II) sulphate is blue.

b. Form different oxidation numbers.c. Form complex ions: MnO 4, Cr 2O7

2-, CrO 42-, etc.

d. Useful as a catalyst in industries.e. Example:

Iron: Haber process in the manufacture of ammonia

N2 + 3H 2 Fe 2NH 3

Vanadium (V) Oxide: Contact process in the manufacture of sulphuric acid

2SO 2 + O 2 2SO 3

Platinum: Ostwald process in the manufacture of nitric acid

EXERCISE

1. The table below shows the number of neutron and relative atomic mass of eightelements represented as P, Q, R, S, T, U and W.

Element P Q R S T U V W

Number of neutron in an atom 12 12 14 14 16 16 18 22

Relative atomic mass 23 24 27 28 31 32 35 40

Number of proton in an atom 11 12 13 14 15 16 17 18

Electron arrangement of an atom 2.8.1 2.8.2 2.8.3 2.8.4 2.8.5 2.8.6 2.8.7 2.8.8

a. i. Complete the above table by writing the number of proton and electron

arrangement for the atom of each element.





2. Diagram 4 shows part of the Periodic Table of Elements. X, Y, A, B, D, E and F donot represent the actual symbol of the elements.

a. State the position of element B in the Periodic Table.Period 3, Group 13

b. Choose an element that

i. is monoatomic Y ii. forms acidicoxide

D/E iii. has atoms thathave no neutron

X

iv. is an alkali metal A/F v formsamphotericoxide

B vi. has a protonnumber 15

D

vii. is mostelectropositive

F viii. forms basicoxide

A/F ix. forms colouredcompound

G

c. Arrange Y, A, B, D and E according to the order of increasing atomic size.Y, E, D, B, A

d. Compare electronegativity of element D and element E. Explain your answer.- Element E is more electronegative than element D.- Atom E and atom D have same number of shells occupied with

electrons.- The number of proton in the nucleus of atom E is more than atom D.- The strength of nucleus in atom E to attract electron is stronger than

that in atom D

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Jadual Berkala Bi