Some of the boxes in the given table have question marks. Fill in the correct information. Table: Distribution of electrons in different shells and electronic configuration Element Symbol No. of electrons Distribution of electrons in different orbits Electronic configuration Valence electron K L M N Hydrogen H 1 1 1 1 Lithium Li 3 2 1 2 , 1 1 Carbon C 6 2 ? ? ? Oxygen O 8 ? ? ? ? Sodium Na 11 2 ? 1 2 , 8 , 1 ? Aluminium Al 13 2 8 ? ? ? Phosphorous P 15 2 8 ? ? ? Chlorine Cl 17 ? ? ? ? ? Argon Ar 18 2 8 8 ? ? Potassium K 19 2 8 8 ? ? 1 Calcium Ca 20 ? ? ? 2 ? ?

Electronic configuration is the distribution of electrons in different orbits of an atom and valence electrons are the number of electrons present in the outermost shell of an atom. Therefore, the given table can be completed as, Element Symbol No. of electrons Distribution of electrons in different orbits Electronic configuration Valence electron K L M N Hydrogen H 1 1 1 1 Lithium Li 3 2 1 2 , 1 1 Carbon C 6 2 4 2 , 4 4 Oxygen O 8 2 6 2 , 6 6 Sodium Na 11 2 8 1 2 , 8 , 1 1 Aluminium Al 13 2 8 3 2 , 8 , 3 3 Phosphorous P 15 2 8 5 2 , 8 , 5 5 Chlorine Cl 17 2 8 7 2 , 8 , 7 7 Argon Ar 18 2 8 8 2 , 8 , 8 8 Potassium K 19 2 8 8 1 2 , 8 , 8 , 1 1 Calcium Ca 20 2 8 8 2 2 , 8 , 8 , 2 2

In the table given below, the number of protons in the atoms of some elements and their mass numbers are given. Can you write down the number of neutrons for each? Table: Atomic number and mass number Element Symbol Number of protons Mass number No. of neutrons Hydrogen H 1 1 Lithium Li 3 6 Carbon C 6 12 Oxygen O 8 16 Sodium Na 11 23 Aluminium Al 13 27 Phosphorous P 15 31 Chlorine Cl 17 35 Argon Ar 18 40 Potassium K 19 39 Calcium Ca 20 40

The atomic number of an element is equal to the number of protons found in the nucleus of an atom. Mass number is the sum of number of protons and neutrons. Therefore, the given table can be completed as, Element Symbol Number of protons Mass number No. of neutrons Hydrogen H 1 1 0 Lithium Li 3 6 3 Carbon C 6 12 6 Oxygen O 8 16 8 Sodium Na 11 23 12 Aluminium Al 13 27 14 Phosphorous P 15 31 16 Chlorine Cl 17 35 18 Argon Ar 18 40 22 Potassium K 19 39 20 Calcium Ca 20 40 20

Write the electronic configuration of the following: Na 23 11 , C 6 12 , Cl 17 35

Electronic configuration is the distribution of electrons in different orbits. The atomic number of sodium is 11 . Therefore, the electronic configuration of Na 23 11 is 2 , 8 , 1 . The atomic number of carbon is 6 . Therefore, it has 6 electrons in it. Its electronic configuration is 2 , 4 . It has four electrons in its outermost shell. The atomic number of chlorine is 17 . That is, it has 17 electrons in it. Therefore, its electronic configuration is 2 , 8 , 7 .

Exercise 1

Author:Chhattisgarh Board

Chhattisgarh Board Science Solutions for Exercise 1

Simple step-by-step solutions to Exercise 1 questions of Atomic Structure from Science (Theory & Practical) Class-9. Also get 3D topic explainers, cheat sheets, and unlimited doubts solving on EMBIBE.

Questions from Exercise 1 with Hints & Solutions

HARD

9th Chhattisgarh Board

IMPORTANT

Science (Theory & Practical) Class-9>Chapter 3 - Atomic Structure>Questions>Q 2

On what basis did Thomson challenge the theory of indivisibility of atom?

HARD

9th Chhattisgarh Board

IMPORTANT

Science (Theory & Practical) Class-9>Chapter 3 - Atomic Structure>Exercise 1>Q 1

Draw the atomic structures of the elements having $19$ and $20$ electrons.

HARD

9th Chhattisgarh Board

IMPORTANT

Science (Theory & Practical) Class-9>Chapter 3 - Atomic Structure>Exercise 1>Q 1

Some of the boxes in the given table have question marks. Fill in the correct information.

Table: Distribution of electrons in different shells and electronic configuration

Element	Symbol	No. of electrons	Distribution of electrons in different orbits				Electronic configuration	Valence electron
Element	Symbol	No. of electrons	$K$	$L$	$M$	$N$	Electronic configuration	Valence electron
Hydrogen	$H$	$1$	$1$				$1$	$1$
Lithium	$Li$	$3$	$2$	$1$			$2, 1$	$1$
Carbon	$C$	$6$	$2$	?			?	?
Oxygen	$O$	$8$	?	?			?	?
Sodium	$Na$	$11$	$2$	?	$1$		$2, 8, 1$	?
Aluminium	$Al$	$13$	$2$	$8$	?		?	?
Phosphorous	$P$	$15$	$2$	$8$	?		?	?
Chlorine	$Cl$	$17$	?	?	?		?	?
Argon	$Ar$	$18$	$2$	$8$	$8$		?	?
Potassium	$K$	$19$	$2$	$8$	$8$	?	?	$1$
Calcium	$Ca$	$20$	?	?	?	$2$	?	?

HARD

9th Chhattisgarh Board

IMPORTANT

Science (Theory & Practical) Class-9>Chapter 3 - Atomic Structure>Exercise 1>Q 1

In the table given below, the number of protons in the atoms of some elements and their mass numbers are given. Can you write down the number of neutrons for each?

Table: Atomic number and mass number

Element	Symbol	Number of protons	Mass number	No. of neutrons
Hydrogen	$H$	$1$	$1$
Lithium	$Li$	$3$	$6$
Carbon	$C$	$6$	$12$
Oxygen	$O$	$8$	$16$
Sodium	$Na$	$11$	$23$
Aluminium	$Al$	$13$	$27$
Phosphorous	$P$	$15$	$31$
Chlorine	$Cl$	$17$	$35$
Argon	$Ar$	$18$	$40$
Potassium	$K$	$19$	$39$
Calcium	$Ca$	$20$	$40$

HARD

9th Chhattisgarh Board

IMPORTANT

Science (Theory & Practical) Class-9>Chapter 3 - Atomic Structure>Exercise 1>Q 2

You may know that the nucleus is $10^{5}$ times smaller than an atom. We also know that both neutrons and protons are present in the nucleus. Now, the size of the sodium atom is $1.86 \times 10^{- 10} m$ . Can you answer the following questions about the sodium atom:

$1$ . What will be the size of its nucleus?

$2$ . Keeping in mind the ratio of the size of the nucleus to the atomic size, how will you show a sodium atom? Can you pictorially depict a sodium atom accurately?

MEDIUM

9th Chhattisgarh Board

IMPORTANT

Science (Theory & Practical) Class-9>Chapter 3 - Atomic Structure>Questions>Q 1

If the atomic number of an atom is $15$ and mass number is $31$ then what is the number of sub-atomic particles present in the atom?

MEDIUM

9th Chhattisgarh Board

IMPORTANT

Science (Theory & Practical) Class-9>Chapter 3 - Atomic Structure>Questions>Q 2

If the $K$ and $L$ shells of an atom are full and the $M$ shell has $2$ electrons then what is the atomic number of the atom?

HARD

9th Chhattisgarh Board

IMPORTANT

Science (Theory & Practical) Class-9>Chapter 3 - Atomic Structure>Questions>Q 3

Write the electronic configuration of the following:

${}_{23}^{11}{Na}, {}_{6}^{12}C, {}_{17}^{35}{Cl}$

Exercise 1

Chhattisgarh Board Science Solutions for Exercise 1

Questions from Exercise 1 with Hints & Solutions

Learn and Prepare for any exam you want !