You have understood certain periodic trends in the periodic table?.Based on these tick the correct answer in the table given below. Trends Down the group Across the period Size of atom decreases/increases decreases/increases Metallic character decreases/increases decreases/increases Non-metallic character decreases/increases decreases/increases Ionisation energy decreases/increases decreases/increases Electronegativity decreases/increases decreases/increases

a. Size of atom: It increases down the group because the number of shells increases down the group. They remain the same across the period and nuclear charge increases. Hence, the size of the atom decreases across the period b. Metallic character: It increases down the group because the force of attraction between the nucleus and outermost election decreases due to the addition of shells. Across the period metallic character decreases because of an increase in nuclear charge. c. Non-metallic character: It decreases down the group because of less force of attraction between the nucleus and outermost electron. It increases across the period because of increasing nuclear charge. Hence, the electrons tightly bound to the atom. d. Ionisation energy: It decreases down the group as less force of attraction between the nucleus and outermost electron because of the addition of more shells. It increases across the period because of increasing nuclear charge. Hence, the electrons tightly bound to the atom. So more energy is required to remove the electron. Size of atom Down the group Across the period Size of atom increases decreases Metallic character increases decreases Non-metallic character decreases increases Ionisation energy decreases increases Electronegativity decreases increases e. Electronegativity: It decreases down the group because of less force of attraction between the nucleus and outermost electron because of the addition of more shells. So an atom can not attract electrons strongly. It increases across the period because of increase in the nuclear charge. Valence shells are more than half-filled towards the right side of the periodic table, so these atoms try to gain electrons. So electronegativity increases.

The table given below lists the contributions and names of scientists who made earlier attempts in the classification of elements. Fill in the blanks. Contribution/Findings Name of scientists Triads _____ _____ Newlands Classification of elements into metals and non-metals _____ Modern periodic law _____

Dobereiner formed small groups of three elements showing similar properties. These groups were called Triads. In 1864 when Newlands arranged all the known elements at that time in the increasing order of atomic mass, he found that the properties of the eight-element are the repetition of those of the first element. He compared this to the seven notes of music. This law is known as the Law of Octaves. It was Lavoisier who first made an attempt to classify elements. In 1789 , he classified the elements into metals and non-metals. After Lavoisier, it was Dobereiner who gave a notable contribution in the classification of elements. Moseley, through his X-ray diffraction experiments, gave serial numbers to the elements. It was called the atomic number. Based on this the periodic law was modified and it is known as the modern periodic law. Contribution/Findings Name of scientists Triads Dobereiner Law of Octaves Newlands Classification of elements into metals and non-metals Lavoisier Modern periodic law Moseley

Complete the table. Element Atomic No. Electronic configuration Group Number Period Number Lithium _____ 2 , 1 1 2 Oxygen 8 _____ _____ _____ Argon 18 _____ _____ _____ Calcium _____ 2 , 8 , 8 , 2 _____ _____

Element Atomic No. Electronic configuration Group Number Period Number Lithium 3 2 , 1 1 2 Oxygen 8 2 , 6 16 2 Argon 18 2 , 8 , 8 18 3 Calcium 20 2 , 8 , 8 , 2 2 4 The period number is equal to the number of electron occupied shells in the element. The group of an element is predicted from the number of electrons in the valence shell. If the element is in the p block, then the number of the group can be determined by the formula: (number of valence electrons + 10 ). For s block elements, the group number is equal to the number of valence electrons.

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What happens to the electronegativity when we move across a period?

Important Questions on Periodic Table

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Chemistry Standard IX Part 1>Chapter 4 - Periodic Table>Exercise 1

Where will be the position of the elements with high electronegativity in the periodic table?

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Chemistry Standard IX Part 1>Chapter 4 - Periodic Table>Exercise 1

Where will be the position of the elements with low electronegativity in the periodic table?

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Chemistry Standard IX Part 1>Chapter 4 - Periodic Table>Exercise 1

What is the relationship between electronegativity and the size of an atom?

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Chemistry Standard IX Part 1>Chapter 4 - Periodic Table>Exercise 1

Is there any relationship between electronegativity and metallic and non-metallic characters? Explain.

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Chemistry Standard IX Part 1>Chapter 4 - Periodic Table>Exercise 1

Is a highly electronegative element a metal or a non-metal. Then, what about those having low electronegativity? Find out?

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Chemistry Standard IX Part 1>Chapter 4 - Periodic Table>Exercise 1

You have understood certain periodic trends in the periodic table?.Based on these tick the correct answer in the table given below.

Trends	Down the group	Across the period
Size of atom	decreases/increases	decreases/increases
Metallic character	decreases/increases	decreases/increases
Non-metallic character	decreases/increases	decreases/increases
Ionisation energy	decreases/increases	decreases/increases
Electronegativity	decreases/increases	decreases/increases

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9th Kerala Board

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Chemistry Standard IX Part 1>Chapter 4 - Periodic Table>Let us assess>Q 1

The table given below lists the contributions and names of scientists who made earlier attempts in the classification of elements. Fill in the blanks.

Contribution/Findings	Name of scientists
Triads	_____
_____	Newlands
Classification of elements into metals and non-metals	_____
Modern periodic law	_____

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9th Kerala Board

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Chemistry Standard IX Part 1>Chapter 4 - Periodic Table>Let us assess>Q 2

Complete the table.

Element	Atomic No.	Electronic configuration	Group Number	Period Number
Lithium	_____	$2, 1$	$1$	$2$
Oxygen	$8$	_____	_____	_____
Argon	$18$	_____	_____	_____
Calcium	_____	$2, 8, 8, 2$	_____	_____

What happens to the electronegativity when we move across a period?

Important Questions on Periodic Table

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