Model Test Questions XI Chemistry
Test # 1 for Chapter # 2
(Atomic structure)
Short Questions-Answers
Q1.Write down short note on subatomic particles.
Q2. Give 5 points of differences between:
(i) Alpha, beta and gamma rays
(ii) Continuous spectrum and Line Spectrum
(iii) Monochromatic and Polychromatic Light
Q3. Complete and balance the following nuclear reactions:
Q4. What is quantum and photon? Write down main points of quantum theory.
Q5. What is radioactivity? How was this process discovered? Write down contribution of Marie Currie and Pierre Currie. Describe an experiment to separate 3 types of nuclear radiations.
Q6. What is spectrum and spectroscopy? Define atomic emission and absorption spectrum. What is the importance of line spectrum? Describe two types of line spectrum.
Q7. Write down 5 uses of nuclear radiations.
Q8. What is the Relationship between Wavelength of X-rays and Nuclear Charge of Atom & how did Atomic Number discover by Moseley?
Long Questions-Answers
Q9. What are X-rays? How are they produced? Give their properties, types and uses. Describe role of X-rays in Moseley’s contribution.
Solutions of Short Questions-Answers Test # 1
Q1. Write down short note on subatomic particles.
Answer
Subatomic Particles
More than 100 subatomic particles have been discovered such as electron, proton, neutron, positron, mesons, hyperons, neutrino, antineutrino, muon etc.
Fundamental particles
Out of 100 subatomic particles, only electron, proton and neutron are considered to be fundamental particles of an atom as they play an important role for the determination of physical and chemical properties of element.
Almost all of the mass of an atom exists in nucleus and nucleus was discovered by Rutherford (in 1911 A.D.). Except protium (lightest isotope of hydrogen), nuclei of all other atoms contain neutrons.
Properties of Subatomic Particles
Electrons
Discovery -------- J.J. Thomson in 1897 A.D (Crook’s discharge tube with perforated cathode)
Location -----------Orbits (100,000 times greater volume than nucleus but form less than one percent total)
Charge -----------negative equal to positive charge of protons
Mass ------------nearly 1836 times less than proton and 1839 times less than neutrons.
Attractive Force -------- electrostatic force keeps electrons constantly moving around nucleus
Protons
Discovery ----------Goldstein (1886 A.D) (cathode rays experiment, positive rays beam)
Location -----Nucleus
Charge ------ Positive equal to negative charge of electrons
Mass ------------ nearly 1836 times than electron.
Attractive Force ------Nuclear forces
Atomic Number -----No. of protons
Mass number ------ Sum of no. of protons and neutrons
Neutrons
Discovery ------------ James Chadwick (1932 A.D) (artificial radioactivity experiment, alpha-neutron reaction of Be)
Location -----------------Nucleus
Charge ------------------NONE OR NETURAL (not deflected by electric or magnetic fields)
Mass ------------------- nearly 1836 times than electron (slightly heavier than protons)
Attractive Force -------Nuclear forces (stability of nucleus depends upon the neutrons)
Atomic Number --------- No. of protons
Number of neutrons ---Mass number–Number of protons
Q2.Give 5 points of differences between:
(i) Alpha, beta and gamma rays
(ii) Continuous spectrum and Line Spectrum
(iii) Monochromatic and Polychromatic Light
Distinction between Alpha, beta and gamma rays
Distinction between Continuous and Line Spectrum
Distinction between Monochromatic and Polychromatic Light
Q3. Complete and balance the following nuclear reactions:
Q4. What is quantum and photon? Write down main points of quantum theory.
Quantum
The emission or absorption of energy (light) occurs in small packets of energy or specified amount called quanta which is defined as the smallest unit of radiation energy which can exist independently.
Photon
A quantum of radiant energy in the form of light is called Photon.
Basic Postulates of PQT
This theory explains the nature of light in terms of Quanta which is the smallest unit of radiation energy.
1.Atoms cannot absorb or emit energy continuously.
2. The emission or absorption of energy (light) occurs in small packets of energy called quanta.
3. The amount of energy of quantum is directly proportional to the frequency of the radiations emitted or absorbed by the body. i.e.
E 𝛂 u or E = hu (This is called as Planck’s equation)
Where,
E = Energy gained or lost by body.
h =Planck’s constant = 6.625 x 10–34 J.s (6.625 x 10–27 Ergs.sec).
u = Frequency of radiation
Q5. What is radioactivity? How was this process discovered? Write down contribution of Marie Currie and Pierre Currie. Describe an experiment to separate 3 types of nuclear radiations.
Definition
Radioactivity is the nuclear phenomenon in which there is a spontaneous and continuous emission of nuclear radiations from atom whose atomic number is greater than 83 due to the splitting of atomic nuclei.
Discovery and First Radioactive element discovered
The phenomenon of radioactivity was discovered by a French professor, Henry Becquerel in 1896 A.D. while working on uranium mineral called Pitch-blende (an oxide of uranium; U3O8). He observed that there was continuous emission of some invisible radiations which producing bright spots on (fogging) photographic plates, ionizing gases, penetrating through thin metal sheets and producing fluorescence on zinc sulphide screen. This process of emitting invisible radiations was termed as radioactivity.
Discovery Polonium and Radium By Marie Currie and Pierre Currie
Marie Currie and her husband, Pierre Currie isolated the radioactive component of the pitch blend mineral and separated two new radioactive elements polonium and radium.
Experiment for Separation and Detection of Radiation
To study the nature of radiations, Rutherford placed a small piece of radioactive material is in a Lead Block having a small hole in it. The radiations emitted by radioactive substance were passed through an electric field. (In fact, they are first subjected to pass through a vacuum chamber with a photographic plate in which a magnetic or electric field is applied).
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