IX Chemistry - Chapter 4 - Periodicity of Elements and Periodic Table

Definitions

Periodic Table

A table of elements obtained by arranging them in order of their increasing atomic number in which elements having similar properties are placed in the same group is called Periodic Table.

Group

The vertical column of elements in the periodic table are called Groups.

Period

The horizontal rows of elements in the periodic table are called Periods.

Periodicity

The repetition of physical and chemical properties of elements periodically is called Periodicity of Properties.

Periodic Law

Physical and chemical properties of elements are periodic function of their atomic masses.

Metal

Elements which are good conductors of heat and electricity are malleable and ductile and have a metallic luster are called Metals like Sodium, Potassium, Gold, Copper etc.

Non-Metals

Elements which are non or bad conductor of heat and electricity are neither malleable or ductile and have no metallic luster are called Non-Metals like Carbon, Nitrogen, Chlorine etc.

Metalloids

Metalloids are semi metals have the properties which are intermediate between a metal and non-metal like Boron, Silicon, Germanium, Arsenic, Antimony etc.

Law of Triads

A German Chemist, Dobereiner (1829), arranged chemically similar elements in groups of three on the basis of their atomic masses called Triads and it was found that atomic mass of the middle element was approximately equal to the average of atomic masses of other two elements. This is known as Law of Triads.

Drawback or Defect

As very few elements could be arranged in such groups, this classification did not get wide acceptance.

Law of Octaves

An English Chemist Newland (1864) stated that if the elements were arranged in the ascending order of their atomic masses, every eight element will have similar properties to the first. This is knows as Law of Octaves.

Drawback or Defects

1. Noble gases were not discovered at that time and no place was reserved for the undiscovered noble gases.

2. In the same way no blank spaces for the undiscovered elements were present in his table.

Mendeleyv's Period Table and Periodic Law

Russian Chemist, Mendeleyv's (186) who wa working separately from Lother Mayer published a table of elements.

According to Mendeleyv's when the element were arranged in order of their increasing atomic mases, the elements with similar properties were repeated after regular interval and were placed one above the other.A table obtained in this manner is called Periodic Table. Mendeleyv's stated this periodicity in the form of Periodic Law.

Important Features of Mendeleyv's Periodic Table

---

The important features of Mendeleyv's Periodic table are:

Periods and Groups

The horizontal rows which run from left to right in Periodic Table are called Periods and they are twelve in number.

The vertical rows which run from top to bottom in periodic table are called groups and they are eight in number.

Vacant Spaces

Mendeleyv's left many vacant spaces for the still unknown elements. For example, next to Calcium (40) should be Titanium (48) but it resembled silicon (28) instead of Aluminium (27). He left vacant space for element with atomic mass 44.

Discovery of New Element

Mendeleyv's discovered new elements and also guessed their atomic mass and properties.

Atomic Mass Correction

Mendeleyv's corrected the atomic masses of certain elements on basis of their properties and provided proper place to them in the periodic table.

Defects in Mendeleyv's Periodic Table

---

The Mendeleyv's Period Table has following defects:

Irregular Position of Some Elements

According to Mendeleyv's Periodic Law Potassium (39) should be placed before Argon (40) but he placed Argon (40) before Potassium (39) which goes against his law.

Position of Isotopes

Mendeleyv's periodic table gives no indication about the position of isotopes.

Structure of Atom

Mendeleyv's Periodic table gives no idea about structure of atoms.

Position of Lanthanides and Actinides

Lanthanides and Actinides have not been given proper place in Periodic Table.

Coinage and Alkali Metals

Alkali metals and coinage metals with different properties are placed in the same group. This defect has been replaced by placing them into two sub groups.

Modern Periodic Law and Modern Periodic Table

Modern Periodic Law

Physical and chemical properties of the elements are periodic function of their atomic number. Mosely (1913) says that atomic mas is not fundamental property. Due to some defects present in Mendeleyv's periodic law, Mosely introduced the concept of anomic number for the elements.

Example

When isotopes were discovered, it was thought advisable to arrange the elements on basis of their atomic number instead o increasing atomic mases. Isotopes were needed different position in the Mendeleyv's periodic table. Hence Mendeleyv's periodic law was modified.

Modern Periodic Table

When Mendeleyv's periodic law was modified and new elements were discovered. This forcd the scientists to change Mendeleyv's periodic law.

The electronic configuration of atoms also played an important role in he arrangement of the modern periodic law. This form of periodic table is called "Long form of Periodic Table" because it contains eighteen groups instead of eight but seven periods instead of twelve.

Group I - The Alkali Metals

The elements of group I are called "Alkali Metals". The word alkali is derived from an Arabic word meaning Ashes.

Elements of Group I

• Lithium

• Sodium

• Potassium

• Rubidium

• Cesium

• Francium

Properties of Group I

1. They are mono atomic.

2. They exist in solid metallic state.

3. Outer most shell of these elements is incomplete having one electron.

4. Elements of this group are highly reactive.

5. Elements of this group have large tendency to form compounds.

6. Elements of this group are strongly electro-positive.

Group II - The Alkaline Earth Metals

The elements of group II are called Alkaline Earth Metals. These elements occur in nature as silicate mineral and their oxides and hydroxides are strongly basic. Therefore these elements are called Alkaline Earth Metals.

Elements of Group II

• Beryllium

• Magnesium

• Calcium

• Strontium

• Barium

• Radium

Properties of Group II

1. They are mono atomic.

2. They exist in solid state.

3. Outer most shell of these elements is incomplete having two electrons.

4. Elements of this group are moderately reactive.

5. Elements of this group have moderate tendency to form compounds.

Group III - The Boron or Aluminium Family

The elements of group III exist in solid state.

Elements of Group III

• Boron Metalloid

• Aluminium Metal

• Gallium Metal

• Indium Metal

• Thallium Metal

Properties of Group III

1. They are mono atomic.

2. They exist in solid state.

3. Outer most shell of these elements is incomplete having three electrons.

4. Elements of this group are quite reactive.

5. Elements of this group have moderate tendency to form compounds.

Group IV - The Carbon and Silicon Family

Elements of Group IV

• Carbon

• Silicon

• Germanium

• Tin

• Lead

Properties of Group IV

1. They are mono atomic.

2. They exist in solid state.

3. Outermost shell of these elements is incomplete.

4. Elements of this group are quite reactive.

5. Elements of this group have moderate tendency to form compounds.

Group V - The Nitrogen Family

Elements of Group V

• Nitrogen

• Phosphorus

• Arsenic

• Antimony

• Bismuth

Properties of Group V

1. Some are mono atomic and some are di-atomic.

2. Some of them exist in gaseous and some are in solid state.

3. Outermost shell of these elements is incomplete having five electrons.

4. elements of this group are quite reactive.

5. Elements of this group have quite tendency to form compound.

Group VI - The Oxygen Family

Elements of Group VI

• Oxygen

• Sulphur

• Selenium

• Tellurium

• Polonium

Properties of Group VI

1. Some are mono atomic and some are di-atomic.

2. Some of them exist in gaseous and some are in solid state.

3. Elements of this group have quite tendency to form compounds.

4. The tendency of forming covalent bond decreases from oxygen to polonium.

5. There is a gradual decrease in the ionization potential down the group.

Group VII - The Halogen Family

Elements of Group VII

• Fluorine Gas

• Chlorine Gas

• Bromine Liquid

• Iodine Solid

• Astatine Radioactive

Properties of Group VII

1. They are diatomic except At.

2. Halogens are very active non-metals.

3. Outer most shell of these elements is incomplete having seven electrons.

4. Elements of this group are highly reactive.

5. There is a gradual decrease in the ionization potential down the group.

Transition Elements

Definition

Elements in Group IB, IIB, through VIIB are known as Transition Elements because they show their properties which are transitional between higly reactive and strong electro-positive elements of S-block which form ionic compounds and p-block elements which form largely covalent compounds.

Properties of Transition Elements

1. Transition Elements have incomplete inner electron shells.

2. They show variable valency.

3. They show similar behaviour.

4. They all are metals.

5. They have strong inner atomic bonds.

Group 0, The Noble Gases

The elements of Group VIII A are called "Noble Gases" or "Inert Gases" or "Zero Group Elements".

Elements of Group 0

• Helium

• Neon

• Argon

• Krypton

• Xenon

• Radon

Properties of Group 0

1. They are mono atomic.

2. They exist in gaseous state.

3. Outer most shell of these elements is either complete or contains eight electrons.

4. These elements are mostly chemically non-reactive.

5. These elements have no tendency to form compounds (only a few of these compounds are known).

Atomic Radius

Definition

One half of the distance between the nucleus of two identical atoms when these are in close contact with each other is called Atomic Radius.

Unit

It is measured in angstrom unit A.

Trend in Period

The atomic radii decreases from left to right within a period in the periodic table. This is because nuclear charge increases with the increase of atomic number. But the number of shells remains same within a period.

Trend in Group

Atomic radius increases from top to bottom in a group. This is because, although nuclear charge increases from top to bottom but at the same time on new shell is also added for each successive element down the group.

Ionization Energy (I.E) or Ionization Potential (I.P)

Definition

The minimum energy needed to remove an electron from an isolated, gaseous atom in its ground state is called Ionization Energy.

Unit

It is expressed in electron volts or kilo-joules permole.

1 ev = 96.49kj

Factors Affecting Ionization Energy

The ionization energy of elements depends upon the following factors:

1. Effect of Nuclear Charge on I.E

The greater the nuclear charge the higher is the ionization energy.

2. Effect of Atomic Size

The larger the size of atom the lower is the ionization energy.

Trend of I.E in Period

Ionization energy increases from left to right in a period due to increase in nuclear change and decrease in atomic size.

Trend of I.E in Group

I.E decreases from top to bottom in a group due to increase in atomic size.

Electronegativity

Definition

The tendency of each atom in a covalent molecule to attract a shared pair of electrons towards itself is known as its electronegativity.

Factors Affecting Electronegativity

Electronegativity depends upon the following factors:

• Atomic size

• Atomic Number

• Electron Affinity

• Ionization Energy

Trend or Variation in the Period

Electronegativity increases from left to right within a period due to increase in nuclear charge and decrease in atomic size.

Trend or Variation in the Group

Electronegativity values decreases from top to bottom within a group due to increase in atomic size.

Electron Affinity

Definition

The energy change that occurs when an electron is gained by an atom in the gaseous state is known as Electron Affinity.

Electron Affinity for the addition of first electron is negative i.e. energy is released but for further addition of electrons it is positive because energy has to be added to over come repulsion between negative ion and electron.

Unit

It is measured in KJ/mol or in e.v per atom.

Factors Affecting Electron Affinity

• Atomic Size

• Nuclear Charge

Tend or Variation of Electron Affinity in Group

Down the group in the periodic table, electron affinity decreases because the addition of a new shell to each atom decreases its force of attraction.

Trend or Variation of Electron Affinity in Period

In a period, the electron affinity increases from left to right because the incoming successive atoms have higher nuclear charge and attract electron more towards itself.

Chapter 4- The Cell

CELL

It is the basic structural and functional unit of life, which is able to carry out all the life processes.

CELL THEORY

The cell theory was collectively proposed by “Schleiden(1838), Schawnn(1839) and Virchow (1858).

IMPORTANT POSTULATES

The fundamental points of the cell theory are:

(a) The cell is the structural and functional unit of all living organism.

(b) All organisms are composed of one or more cells.

(c) New cells can arise only by division of pre-existing cells.

Thus cell theory established the concept that the function of an organism is the result of activities and interaction of the cell units.

MICROSCOPE

DEFINITION

An instrument with the help of which we see small, tiny and minute objects which can’t be observe by naked human eye.

TYPES OF MICROSCOPE

There are three main types of microscope.

1. LIGHT MICRO SCOPE

In this microscope visible light is used as source of illumination.

2. X-RAY MICROSCOPE

X-Rays are used as source of illumination.

3. ELECTRON MICROSCOPE

Electron beam is used as source of illumination.

There are further two sub-types of electron microscope which are:

(A)TRANSMISSION ELECTRON MICROSCOPE

In this type resultant image is obtained on a fluorescent screen or photographic film.

(B)SCANNING ELECTRON MICROSCOPE

In this type resultant image is obtained on a television screen.

MAGNIFICATION OF MICROSCOPE

Ability of microscope to increase the shape and size of the objects image. It can be calculated by multiplying the power of its eye pieces with its magnifying power of its objective.

RESOLUTION OF MICROSCOPE

The capacity of microscope to separate adjacent forms or object. Also known as “Minimum Resolved Distance”.

CONTRAST

It is important to distinguishing one part of cell from another.

• (Difference between light and electron microscope – From Text page #57)

• Prokaryotes and eukaryotes – From Text page #58)

CELL MEMBRANE

Each cell is covered by an asymmetrical, porous, thin, semi permeable sheet called cell membrane or plasmalemma.

CHARACTERISTICS OF CELL MEMBRANE

Living part of the cell, consist of lipid + protein.

• 1.5 micron in thickness.

• Consist of two layers of lipid.

• Lipid of plasma membrane are,

1. Phospho-lipids

2. Glycolipids

3. Sterol

4. Cholesterol.

STRUCTURE OF CELL MEMBRANE

Cell membrane made up of phospho-lipids bilayer and each layer consists of ,

1. Head (hydrophilic end)

2. Tail (hydrophobic end)

HEAD (HYDROPHILIC/POLAR END)

Present towards the surface and formed of phosphates.

TAIL (HYDROPHOBIC/NON-POLAR END)

Present towards the center and formed of fatty acids.

The non-polar ends of phospho lipids face each other, whereas their polar ends are in association with protein or carbohydrates between every two phospo lipids molecule lies a molecule of “Cholesterol”.

FLUID MOSAIC MODEL

INTRODUCTION

The fluid mosaic, bilayer model was proposed by “Singer and Nicolson (1972).

POSTULATES OF FLUID MOSAIC MODEL

Important postulates of this model are,

(a) The cell membrane consists of lipid bilayer, in which a variety of proteins are present.

(b) These proteins float in the fluid matrix of lipid (as ice bergs in the sea)

(FIGURE 4.4 Page #61)

ARRANGEMENT OF PROTEINS

According to the fluid mosaic model proteins are:

1. INTRINSIC/INTEGRAL PROTEINS

These proteins peneterate the membrane surface and enter the lipid layers (partially or wholly)

2. EXTRINSIC/PERIPHERAL PROTEINS

These are located adjacent to outer and inner surface of membrane and float like ice-berg in the sea.

ARRANGEMENT OF LIPIDS

The non-polar end face each other while their polar ends are towards the surface.

SIGNIFICANCE OF MODEL

• Cell membrane is flexible.

• Can change shape (because the protein and lipid of the membrane can move).

FUNCTION OF MEMBRANE PROTEIN

• Certain proteins themselves act as enzymes.

• Some protein act as carrier for active transport.

• Provide elasticity to membrane.

• Pores are lined by the proteins.

FUNCTION OF LIPIDS PRESENT IN MEMBRANE

• The lipids give rigidity to cell membrane.

• They lower the surface tension.

FUNCTIONS OF CELL MEMBRANE

• It performs the two main function.

• Protection of Protoplasm.

• Regulation of material (In and Out of cell) through its permeabality.

PERMEABILITY OF MEMBRANE

The permeability of membrane is regulated by two processes.

(1) Passive Transport (Osmosis and Diffusion)

(2) Active Transport (Endocytosis, Exocytosis)

1. PASSIVE TRANSPORT

Such type of molecules transport which does not require energy. It is further divided into,

DIFFUSION

Spreading and free movement of molecules (or ions) from the region of higher concentration to the region of lower concentration (till equilibrium state)

SIGNIFICANCE

• Movement of oxygen and digested food (glucose, amino acids, fatty acids) into the cell.

• Movement of excretory waste out of cell.

OSMOSIS

Diffusion of water by semipermeable membrane or the movement of solvent molecules from higher to lower concentration across semi permeable membrane.

SIGNIFICANCE

• Liquids, primarily water molecules enter and leave the cell by Osmosis.

• It helps to maintain a balance (osmotic pressure) in and out of cell.

2. ACTIVE TRANSPORT

Such type of molecule transport which require energy. Or Movement of molecules against the concentration by the expenditure of energy through a carrier (i.e. movement of molecules from the region of lower concentration to higher concentration by protein using ATP as energy.

SIGNIFICANCE

Absorption of excess food (glucose), ions (K+ and Na+) takes place by Active transport.

CONDITIONS

• It is unidirectional.

• ATP provides energy.

• Protein act as carrier.

Active transport is further subdivided into,

(1) Phagocytosis and Pinocytosis (Endocytosis).

(2) Exocytosis.

PHAGOCYTOSIS

Process of picking and ingestion of large solid particle by plasma membrane (which can not enter by diffusion, osmosis or active transport).

SIGNIFICANCE

• Ingestion of solid food particles.

• WBCs pick foreign particles (certain bacteria)

PINOCYTOSIS

Process of fluid intake, for absorbing fluid by forming pinocytic vesicle (the fluid which cannot be absorbed by osmosis, enters through it)

SIGNIFICANCE

Helps in absorption of harmones, lipids etc.

CELL WALL

The cell wall is the outer most covering of a plant cell. It is composed of cellulose (a carbohydrate) and some other chemical substances.

This hard covering gives form, firmness and strength to the plant cell.

In a young cell it is thin and delicate but in a mature cell it becomes thick due to the deposition of various chemical substances on its inner surface.

There are three layer of cell wall.

1. MIDDLE (LAMELLA)

• First formed cell plate.

• Cementing layer between two daughter cells.

• Composed of Ca++ and Mg++ pectate.

• Cells are separated when this layer is dissolved.

2. PRIMARY WALL

• First product of cell synthesized by protoplast.

• In young cells it is thin and elastic while it becomes thick and rigid on maturity.

• Made up of Hemicellulose (50%), cellulose (25%) and pectate substances.

3. SECONDARY WALL

• Composed of cellulose.

• Present inside the primary wall.

• Can be modified through the deposition of lignin and other substances.

NUCLEUS

It control all the activities of the cell and was discovered by Robert Brown in 1831.

It consist of the following parts,

(1) Nuclear Membrane.

(2) Nucleoplasm or Karyoplasm.

(3) Nucleolus.

(4) Chromatin Network.

1. NUCLEAR MEMBRANE

The nucleus is bounded by a double layered membrane which bears pores and is known as “Nuclear Membrane”

2. NUCLEOPLASM

Inside the nuclear membrane is a structure less fluid called “Nucleoplasm” and highly rich with proteins.

3. NUCLEOLUS

It is a patch work of granules rich in R.N.A formed in the nucleus. They may be more than one in a single nucleus. It contains mRNA formed from DNA, later mRNA comes out of nucleus to control protein formation.

4. CHROMATIN NETWORK

There is a network of threads dispersed in the karyoplasm called (Chromatin network)

Each individual thread is called (Chromosomes).

These are made up of DNA and are carrier of genes.

NOTE:(Types of Chromosomes from Book Page# 66)

MEMBRANE BOUND ORGANELLES

(1) ENDOPLASMIC RETUCULUM

It is a complex series of tubules in the cytoplasm. Endoplasmic reticulum are of two types,

(1) Agranular or Smooth EPR.

(2) Granular or Rough EPR.

SMOOTH EPR

• It has no attached ribosome’s.

• Function is to synthesis lipid.

ROUGH EPR

• It has ribosome’s attached to its outer surface.

• Synthesize protein and also transport material within the cell.

(2) MITOCHONDRIA

An oval body bounded by a double membrane. The inner membrane is folded to form shelves/incomplete partitions. Which are known as “Crista”, here oxidative enzyme are present. They are sites for aerobic cellular respiration and the energy is produced. Therefore also known as “Power house of cell”

(3) GOLGI APPARATUS(DICTYOSOMES)

These are thin, plate like structures and are usually located near the nucleus. These are the site of formation of lysosomes and also conjugate protein, modify structure of substances, synthesized by EPR to form lysosomes and secretary vesides. Golgi bodies of plants and lower animals (mostly invertebrates) are known as “Dictyosomes”.

(4) LYSOSOMES

They are large, some what irregular structure formed in the cytoplasm formed by golgi-bodies. They contain hydrolytic enzymes which destroys foreign particles. They are also known as “Suicide Sacs” because after secreting the enzymes they digese their own proteins (Autophagy).

NOTE:(Lysosomal Storage Diseases From Text Page # 71)

(5) PLASTIDS

They are specialized organelles of plant cell that contain pigment or they synthesize reserve substances.

They are of three kinds,

(A) LEUKOPLAST

leuco = white

Leukoplast are colourless and store nutrient material.

(B)CHLOROPLAST

Chloroplast are green having chlorophyll that performs photosynthesis.

(C) CHROMOPLAST

Chromo = Colour

Chromoplast contain different coloured (red, yellow, orange or other than green) pigments. They are found in the cells of different coloured flowers and fruits.

(6) MICRO BODIES

It includes peroxisome and glyoxysome.

(A) PEROXISOME

These are the single membrane bounded microbodies contain enzymes for transferring hydrogen atom to oxygen i.e. forming hydrogen peroxide.

• Hydrogen peroxide is very toxic to the cell therefore it is immediately break down to water by enzyme catalyst.

• These microbodies help in detoxyfication of alcohal and mostly present in liver cells.

(B) GLYOXYSOME

• It is a single layered membrane bound structure containing enzymes which metabolize some molecules in photosynthesis and respiration.

• They also cause oxidation of fatty acids.

CYTOSKELETON

Cytoskeleton means skeleton of the cell, which is mostly composed of microtubules, microfilaments and intermediate filaments.

(A) MICRO TUBULES

• Microtubules are hollow cylinders with an outerdiameter of 25nm.

• They are made up of a special type of globular protein tubulin.

• In single microtubule consist of hundredth of thousands of tubulin sub units, which are usually arranged in 13 columns called Protofilaments.

• Microtubules are arranged in assemble and disassemble manner.

• In animal cells and lower plants they also form centriole, cilia and flagella.

(B) MICROFILAMENTS

• Microfilaments are solid structures, thread like with a diameter of 7nm.

• They are also composed of globular proteins.

• Each microfilament consist of two actin (Protein) chains that inter wing in a helical fashion.

(C) INTERMEDIATE FILAMENTS

• They are intermediate in size having a diameter of 8nm to 11nm.

• They are rope like polymers of Fibrous protein.

• In skin and hair these filaments are made up of protein keratin.

• They provide mechanical strength to the cell and support the nuclear envelope.

NON MEMBRANE BOUND CYTOPLASMIC ORGENELLE

(1)RIBOSOMES

• These are small structures concerned with protein synthesis in all type of the cells i.e. Prokaryotic as well as Eukaryote.

• They are freely dispersed in cytoplasm of Prokaryotic cell but in Eukaryotic cells they may be free or attached with endoplasmic reticulum.

• More than 50 type of proteins are present in ribosome structure and they contain high quantity of RNA.

• Under the direction of Nucleus ribosome produce the protein made it by the cell.

• Each Ribosome consist of two unequal parts.

• These are the smallest and most vital cellular components, manufactured in the nucleolus.

(2) CENTRIOLE

• They are only present in animal cells and certain lower plants.

• Mostly near the nucleus.

• Each centriole consist of two cylinders lying perpendicular to one another.

• Each cylinder consist of nine parallel triplets of hollow cylindrical microtubules.

• During the cell division they replicate and move towards opposite poles of the cell.

• In mitosis and meiosis they form thread like fibers which rediate from each centriole are known as mitotic apparatus.

(3)VACUOLES

• These are non-protoplasmic fluid filled cavities in the cytoplasm.

• Their membrane is known as Tonoplast.

• They are more prominent in mature cells.

• In plant cells vacuoles are filled with cell sap and act as store, house.

• They also play an important role in plant defence.

• In animal cells vacuole contain hydrolytic enzymes (i.e. lysosomes)

(Note: Techniques to isolate components of the cell Text Page # 58).

IX English - Chapter 4 - Moen-Jo-Daro

Question and Answers

Q.1 What does Moen-Jo-Daro means? Where is it situated?

Ans. Moen-Jo-Daro means "Mound of the Dead". It is situated at a distance of 27km from Larkana on the right bank of river Indus.

Q.2 Who was Sir John Marshall?

Ans. Sir John Marshall was an English civil servant, whose work was to look after historical remains, like ancient building and other old things such as these pieces of pots and bricks. He was very interested in history and was anxious to find out about these remains.

Q.3 What did Sir John Marshall remark, when pieces of old pots and bricks were brought to him?

Ans. sir John Marshall was an English civil servant who was interested in old historical remains. So when some villagers brought pieces of old pots and bricks he at once know that they were pieces of historical remains.

He remarked that perhaps these was an ancient city lying under the mound of day and sand. He directed the villagers to dig there in the hope that they would uncover the remains of an ancient city.

Q.4 What was the occupations of the people of Moen-Jo-Daro?

Ans.

• The people of Moen-Jo-Daro were traders. They traded with other cities and traveled from place to place on business.

• They were skilled craft men who worked with gold and silver.

• They were farmers who grew wheat, rice and cotton and they also kept cattle.

Q.5 How was the city of Moen-Jo-Daro planned?

Ans. The city of Moen-Jo-Daro was a well planned and cleaned city. Each house was made of large baked bricks and a bathroom and servant-quarters close by covered drains beside the streets. The streets were made of baked bricks.

There was a great hall where grain were stored. There is a wide road in the middle of which was the shopping centre with shops on both sides.

Q.6 Name any four objects on exhibition in the Moen-Jo-Daro Museum? or Name any four findings of Moen-Jo-Daro?

Ans. The objects found in Moen-Jo-Daro are:

1. A metal statue of a dancing girl.

2. Seals, Gold, Silver and Ivory Jewelery.

3. Painted Pottery

4. Metal tools and weapons.

5. The head of a bull.

Q.7 How old is the civilization of Moen-Jo-Daro?

Ans. The civilization of Moen-Jo-Daro is 4500 years old.

Q.8 How did this civilization come to an end?

Ans. No body knows exactly how this ancient civilization came to an end. Either they were from the north or some great earthquake destroyed them.

Q.9 How do we know Moen-Jo-Daro's probable age? What can help us to know more about civilization?

Ans. We know Moen-Jo-Daro's probable ge from the metal objects found from the execution. We can learn more about this civilization if the language experts are able to determine the meanings of the words written on the seals and the pottery.