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Chemistry Chapters

9th Class Chapter 2 Chemistry Short Questions

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Question: 1
When do electrons emit or absorb energy?
Answer: 1
1-39
As long as electron remains in a particular orbit it does not radiate or absorb energy. The energy is emitted or absorbed only when an electron jumps from one orbit to another.
Question: 2
Define atome according to Dalton?
Answer: 2
2-39
Atom is an indivisible, hard, dense and sphere.
Question: 3
A patient has goiter. How will it be detected?
Answer: 3
3-39
The radioactive isotopes are used as tracers in medicine to diagnose the present of a tumor in human body. Isotope of 1-131 is used for diagnosis of goiter in thyroid gland.
Question: 4
From which word atom derived?
Answer: 4
4-39
Atom is derived from the Latin word"Atomos' meaning indivisible
Question: 5
Do you know any element having no neutrons in its atom.
Answer: 5
5-39
Isotope of hydrogen, protium have one proton and no neutrons in it.
Question: 6
What are defects of Rutherford's atomic model?
Answer: 6
6-39
Following are the defect of Rutherford's atomic model. According to classical theory, electrons being charged particles should release or emit energy continuously and they should ultimately fall into nucleus. If electrons emit energy continuously, they should form a continuous spectrum but iin fact, Line spectrum was observed.
Question: 7
What will be the nature of charge on an atom when it loses an electron or when it gains an electron?
Answer: 7
7-39
When it lose an electron it became positive an when it gain and electron it became negative
Question: 8
Name the particles which determine the mass of an atom?
Answer: 8
8-39
Protons and neutrons determine the mass of an atom.
Question: 9
What is the nature of charge on cathode rays?
Answer: 9
9-39
Their deflection in electric and magnetic field proves that they have negative charge.
Question: 10
How was the shown that atomic muclei are positively charged?
Answer: 10
10-39
The deflection of a few particles proved that there is a center of positive charge in an atom which is called nucleus of an atom.
Question: 11
What is quantum?
Answer: 11
11-39
Quantum means fixed energy. It is the smallest amount of energy that can be emitted or absorbed as electromagnetic radiation.
Question: 12
Define nuclear fission reaction?
Answer: 12
12-39
A reation in which heavy nuclear splits up into two nuclei by absorbing show moving next ions.
Question: 13
A patient has goiter; how will it be detected?
Answer: 13
13-39
Isotopes of iodine = 131 are used for diagnosisof goiter in thyroid gland.
Question: 14
What was teh thickness of gold foil used in ruther ford's atomic model?
Answer: 14
14-39
0.00004 cm thick gold foil was used by Rutherford in his experiment
Question: 15
Which carbon isotope use in carbon dating?
Answer: 15
15-39
C-14 used in carbon dating.
Question: 16
How does electron differ from a neutron?
Answer: 16
16-39
Electrons
1- Electron is the negative charged particle.
2- Electron revolves around the nucleus.
3- Mass of electron is 5.486 x 10-4amu
Question: 17
Define Electronic configuration?
Answer: 17
17-39
"The distribution of electrons around the nucleus in various shells and sub shells according to increasing energy, is called electronic configuration".
Question: 18
Define Isotope?
Answer: 18
18-39
"Isotopes are defined as the atoms of elements that have same atomic number but different mass number.
Question: 19
Write down the isotopes of carbon
Answer: 19
19-39
There are two stable isotopes of carbon12C and13C and one radioactive isotope14C
Question: 20
How is the goiter in thyroid gland detected?
Answer: 20
20-39
Isotope of Iodine -131 is used for diagnosis of goiter in the thyroid gland.
Question: 21
Write two postulates of Bohar's atomic model.
Answer: 21
21-39
The Bohr's atomic model was based upon the followingpostulates
1- Each orbit has a fixed energy that is quantized .
2- The ;hydrogen atom consists of a tiny nucleus and electrons are revolving in one of circular orbits of radius r around the nucleus
Question: 22
Who discovered electron, proton and neutron
Answer: 22
22-39
In 1886, Goldstein discovered positively chrged particles called protons. In 1897, J.J. Thomson found in an atom, the negatively charged particles known as electrons. In 1932 James Chadwick discovered neutron.
Question: 23
State four uses of isotopes .
Answer: 23
23-39
Uses of Isotopes:
1- Radiotherapy
2- Tracer for diagnosis and medicine
3- Archaeological and geological uses.
4- Chemical reactionand structure determination
5- Applications in power generation
Question: 24
How many sub shells are there in second shells?
Answer: 24
24-39
Two shells s and p are present in second shell I.
Question: 25
What is the capacity of shells?
Answer: 25
25-39
The number of electrons accommodated by the shell called capacity of shell.
Question: 26
How the electrons of Na are distributed in different shells?
Answer: 26
26-39
The electronic configuration of sodium will be written in shell as
K L M
2 8 1
Further distribution of electrons in sub shells will be : 1s2, 2s2 , 2p6, 3s1
Question: 27
What is the classical theory of radiation? How does it differ from quantum theory?
Answer: 27
27-39
Classical Theory:
According to it , electrons being the charged particles should release or emit energy continuously and they should ultimately fall into the nucleus.
Question: 28
Explain"Plum pudding"theory.
Answer: 28
28-39
Thomson put forth his 'plum'pudding' theory. He postulated that atoms were colid structure of positively charge with tiny negative particles stuck inside. It is like plums in the pudding.
Question: 29
Define nuclear fission reaction
Answer: 29
29-39
Nuclear fission reaction
Nuclear fission is the type of nuclear reaction in which a radioactive element (23592U) is bombarded with slow moving neutrons thatisotopeof element emits three neutrons and split into some other isotopic elements.
23592 U + 10n _________>13956Ba +9436 Kr +310n +energy
Question: 30
Write down the electronic configuration of Cl ion.
Answer: 30
30-39
Chlorine has atomic number 17 , its electronic confiqurationis following
17Cl= 1s2, 2s2, 2p6, 3s2, 3p5
Question: 31
What are shells?
Answer: 31
31-39
Shells are specific energy levels around nucleus in which electrons revolve. e.g. K, L, M, N.
Question: 32
What is meant by Quantum?
Answer: 32
32-39
Quantum:
Quantum means fixed energy. It is the smallest amount of energy that can be emitted or absorbed as electromagnetic radiation, Quanta are plural of quantum
Question: 33
Give one example each of the use of radioactive isotope in medicine and radiotherapy.
Answer: 33
33-39
Radioactive isotopes used in medicine. Iodine 131 Radioactive isotopes used in Radiotherapy P -32 Sr -90 Co-60
Question: 34
State properties of positive rays ?
Answer: 34
34-39
Porperties of positive rays:
1- These rays travel in a straight line in a direction opposite to cathode rays
2-The nature of positive rays depends upon the nature of gas present discharge tube.
3- The positive rays produced by using hydrogen gas are known as protonss
Question: 35
How is the goiter is thyroid gland detected?
Answer: 35
35-39
Iodine-131 is used for the diagnosis of foiter in thyroid gland.
Question: 36
Write use of Co-6o.
Answer: 36
36-39
Cobalt-60 emits stronglypenetrating gamma rays and hence used for cancer affecting within the body.

Question: 37
What is Dalton's atomic theory?
Answer: 37
37-39
According to Dalton. 1. An atom is an indivisible, hard and ense sphere 2. Atoms of same element are alike. 3. Atom combine in different ways to form compounds.
Question: 38
Differentiate between shell and sub shell.
Answer: 38
38-39
Shell
1- The shells are sub divided into sub shell.
2- The fixed circular orbits which is associated with a definite amount of energy is called shell.
3- K,L,M,N etc. are considered as shell.
Question: 39
Why do isotopes of an element have similar chemical properties?
Answer: 39
39-39
Isotopes have similar chemical properties because these depend upon electronic configuration and isotopes have same electronic configuration, and number of protons

9th Class Chemistry Chapters Short Questions