The position of eight elements in the Modern Periodic Table is given below where atomic numbers of elements are given in parentheses. Period Number 2 Li ( 3 ) Be ( 4 ) 3 Na ( 11 ) Mg ( 12 ) 4 K ( 19 ) Ca ( 20 ) 5 Rb ( 37 ) Sr ( 38 ) Predict the number of valence electrons in Rb .

The number of valence electron in Rb is one. This is because Rubidium is present in the first group and is an alkali metal. The metals present in the group one has one electron in its outermost shell.

The position of eight elements in the Modern Periodic Table is given below where atomic numbers of elements are given in parentheses. Period Number 2 Li ( 3 ) Be ( 4 ) 3 Na ( 11 ) Mg ( 12 ) 4 K ( 19 ) Ca ( 20 ) 5 Rb ( 37 ) Sr ( 38 ) Predict whether K is a metal or non-metal

Its electronic configuration of potassium is 2 , 8 , 8 , 1 . It has one valence electron. So, it belongs to the first group. The first group of elements is called alkali metals. The metallic nature decreases from left to right in the periodic table. The element K is a metal.

The position of eight elements in the Modern Periodic Table is given below where atomic numbers of elements are given in parentheses. Period Number 2 undefined undefined 3 undefined undefined 4 undefined undefined 5 undefined undefined Which one of these elements has the largest atom in size?

The element Rubidium undefined has a larger atomic size because down the group atomic size increases. In general, the atomic radius decreases across a period and increases down a group. Down a group, the number of energy levels (shells) increases, so there is a greater distance between the nucleus and the outermost orbital. This results in an increase in atomic size.

The position of eight elements in the Modern Periodic Table is given below where atomic numbers of elements are given in parentheses. Period Number 2 Li ( 3 ) Be ( 4 ) 3 Na ( 11 ) Mg ( 12 ) 4 K ( 19 ) Ca ( 20 ) 5 Rb ( 37 ) Sr ( 38 ) Arrange Be , Ca , Mg and Rb in the increasing order of the size of their respective atoms.

The increasing order of the atomic size of the above elements is as follows: Be < Mg < Ca < Rb . In general, the atomic radius decreases across a period and increases down a group. Down a group, the number of shells increases, so there is a greater distance between the nucleus and the outermost orbital. This results in an increase in atomic size.

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The position of eight elements in the Modern Periodic Table is given below where atomic numbers of elements are given in parenthesis.

Period Number

2 Li(3) Be(4)

3 Na(11) Mg(12)

4 K(19) Ca(20)

5 Rb(37) Sr(38)

Write the electronic configuration of Ca.

Important Questions on Periodic Classification of Elements

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10th CBSE

IMPORTANT

New Millenium Science - Chemistry Class X>Chapter 5 - Periodic Classification of Elements>PRACTICE QUESTIONS SET>Q 11(b)

The position of eight elements in the Modern Periodic Table is given below where atomic numbers of elements are given in parentheses.

Period Number
$2$	$Li (3)$	$Be (4)$
$3$	$Na (11)$	$Mg (12)$
$4$	$K (19)$	$Ca (20)$
$5$	$Rb (37)$	$Sr (38)$

Predict the number of valence electrons in $Rb$ .

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10th CBSE

IMPORTANT

New Millenium Science - Chemistry Class X>Chapter 5 - Periodic Classification of Elements>PRACTICE QUESTIONS SET>Q 11(c)

The position of eight elements in the Modern Periodic Table is given below where atomic numbers of elements are given in parentheses.

Period Number
$2$	$Li (3)$	$Be (4)$
$3$	$Na (11)$	$Mg (12)$
$4$	$K (19)$	$Ca (20)$
$5$	$Rb (37)$	$Sr (38)$

What is the number of shells in $Sr$ ?

MEDIUM

10th CBSE

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New Millenium Science - Chemistry Class X>Chapter 5 - Periodic Classification of Elements>PRACTICE QUESTIONS SET>Q 11(d)

The position of eight elements in the Modern Periodic Table is given below where atomic numbers of elements are given in parentheses.

Period Number
$2$	$Li (3)$	$Be (4)$
$3$	$Na (11)$	$Mg (12)$
$4$	$K (19)$	$Ca (20)$
$5$	$Rb (37)$	$Sr (38)$

Predict whether $K$ is a metal or non-metal

HARD

10th CBSE

IMPORTANT

New Millenium Science - Chemistry Class X>Chapter 5 - Periodic Classification of Elements>PRACTICE QUESTIONS SET>Q 11(e)

The position of eight elements in the Modern Periodic Table is given below where atomic numbers of elements are given in parentheses.

Period Number
$2$	undefined	undefined
$3$	undefined	undefined
$4$	undefined	undefined
$5$	undefined	undefined

Which one of these elements has the largest atom in size?

MEDIUM

10th CBSE

IMPORTANT

New Millenium Science - Chemistry Class X>Chapter 5 - Periodic Classification of Elements>PRACTICE QUESTIONS SET>Q 11(f)

The position of eight elements in the Modern Periodic Table is given below where atomic numbers of elements are given in parentheses.

Period Number
$2$	$Li (3)$	$Be (4)$
$3$	$Na (11)$	$Mg (12)$
$4$	$K (19)$	$Ca (20)$
$5$	$Rb (37)$	$Sr (38)$

Arrange $Be, Ca, Mg and Rb$ in the increasing order of the size of their respective atoms.

HARD

10th CBSE

IMPORTANT

New Millenium Science - Chemistry Class X>Chapter 5 - Periodic Classification of Elements>PRACTICE QUESTIONS SET>Q 12

Write the electronic configuration of two elements

X

and

Y

whose atomic numbers are

20

and

17

respectively. Write the molecular formula of the compound formed when element

X

reacts with element

Y

. Draw the electron-dot structure of the product and also state the nature of the bond formed between both the elements.

HARD

10th CBSE

IMPORTANT

New Millenium Science - Chemistry Class X>Chapter 5 - Periodic Classification of Elements>PRACTICE QUESTIONS SET>Q 13

Write the number of periods and groups in the Modern Periodic Table. How does the metallic character of elements vary on moving
(a) from left to right in a period, and
(b) down a group?.
Give reason to justify your answer.

HARD

10th CBSE

IMPORTANT

New Millenium Science - Chemistry Class X>Chapter 5 - Periodic Classification of Elements>PRACTICE QUESTIONS SET>Q 14

What is periodicity in properties of elements with reference to the Modern Periodic Table? Why do all the elements of the same group have similar properties? How does the tendency of elements to gain electrons change as we move from left to right in a period? State the reason of this change.

Period Number
2	Li(3)	Be(4)
3	Na(11)	Mg(12)
4	K(19)	Ca(20)
5	Rb(37)	Sr(38)

The position of eight elements in the Modern Periodic Table is given below where atomic numbers of elements are given in parenthesis. Period Number 2 Li(3) Be(4) 3 Na(11) Mg(12) 4 K(19) Ca(20) 5 Rb(37) Sr(38) Write the electronic configuration of Ca.

Important Questions on Periodic Classification of Elements

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The position of eight elements in the Modern Periodic Table is given below where atomic numbers of elements are given in parenthesis.

Period Number

2 Li(3) Be(4)

3 Na(11) Mg(12)

4 K(19) Ca(20)

5 Rb(37) Sr(38)

Write the electronic configuration of Ca.