KPK 11th Class Chemistry Chapter 2 Atomic Structure Short Questions Answers
KPK 11th Class Chemistry Chapter 2 Atomic Structure Short Questions with answers are combined for all 11th class(Intermediate/hssc) Level students.Here You can prepare all Chemistry Chapter 2 Atomic Structure short question in unique way and also attempt quiz related to this chapter. Just Click on Short Question and below Answer automatically shown. After each question you can give like/dislike to tell other students how its useful for each.
Class/Subject: 11th Class Chemistry
Chapter Name: Atomic Structure
Board: All KPK Boards
- Malakand Board 11th Class Chemistry Chapter 2 Atomic Structure short questions Answer
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KPK 11th Class Chemistry Chapter 2 Atomic Structure Short Questions Answers
How didj.j Thomson discover the e/m ratio of the cathode rays?
Characteristics of cathode rays.
- Cathode rays travel in straight lines perpendicular to the cathode surface, unless acted upon by an outside force.
- They produce sharp shadows, if any apaque object placed in their path.
Cathode rays are negatively charged as they bend towards the positive pole of the electric field. - These rays heat the object on which they fall.
- They can move a small light pinwheel placed inside the cathode ray tube indicating that they consist a beam of particles.
- The nature of cathode rays is the same irrespective of the gas used in the tube.
- They produce fluorescence on striking the walls the tube.
- They charge to mass ratio (e/m) of these particles was found to be equal to that of e/m = 1.76 x 108 coulomb per gram.
Name any four properties of the cathode rays.
Properties of cathode easy.
Various experiments ware performed to study the properties of cathode rays. In 1869 Hittorf observed that the object placed inside the tube in the path of these rays cast shadow.
2. In 1870 Crooks demonstrated that cathode rays ware streams of particles, which have kinetic energy & momentum because these rays roll a light pinwheel towards the anode. The wheel begins to rotate in the revers direction if cathode and anode are interchanged.
3. In 1895 J- Perrin showed that cathode rays bend towards the positive pole of electric field. There by showing their negative nature.
4. Cathode rays bend at right angle to the line joining the north & south poles showing their charged nature.
Calculate the distance A° between the nucleus and electron in the 5th orbit of an excited hydrogen atom.
Solution: Distance between nucleus and electron in the 5th orbit in A° =? We know that R = n2/Z×0.529A° Putting the values r = (5)2/2 ×0.529 A° = 13.22A °
What will be the wave number ( of the spectral line of an electron in the 5th orbit of an excited hydrogen atom?
Solution:
n1=2 n2=4
Waves number of the spectral line of an electron in the 5th orbit=?
We know that
V=R (1/n21–1/n22)
The value of R (Ryderbg constant) is 1.0974 107m-1 putting the values we get
v=1.0974 ×107 (1/22)-1/42)m-1
v=1.0974 ×107 (1/4–1/16)
3-1/16=2.056 ×106m-1
How will you differentiate between a continuous and a line spectrum?
Continuous spectrum:
It is that type of spectrum in which various colors are diffused into each other & no colored boundary line can be marked between different colors. E.g. the light emitted by sun gives a continuous spectrum.
Line spectrum:
In this type of spectrum, there is a clear cut boundary between the colour bands. It is also called atomic spectrum. When an element is vaporized on a flame or in an electric arc or in discharge tube. It emits light of characteristic colour by which it may be identified. Different colour represent different wave lengths.
Atomic (line) spectrum is obtained when a gaseous or vaporized element is heated. The electrons in atoms get energy and excited. These electrons on de-excitation, emit radiations of characteristic colour reflecting a particular length. For example sodium imparts golden yellow, to the Bunsen flame. Indicating that it absorbs and then emit radiations in the region of wave length ranging from 580 nm to 600nm. Simalrly barium gives grassy green and calcium gives brick red colour to the Bunsen flame.
How did Moseley discover that the atomic number (Z) is the fundamental property of an element?
In 1935 Moseley showed that the frequencyies of emitted X-rays increases with the number of positive charges on the nuclei of target element & that they increase from element to element by a single electron unit. This number of positive charge on the nucleus of an atom of an element is called atomic number denoted by Z. as each proton has a unit positive charge. Thus atomic number of an element is the number of protons contained in the nucleus of an atom.
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