Question

II.
C135
Give short answer for the following question:-
1. What led to modern periodic table?
2. From the Symbol 17
a) Write the mass number
b) Write the number of neutrons,
3. How cathode rays are produced?
4. What do you understand by the term "Energy level"?
5. In which screen anode rays produce fluorescence?​

Answer 1

Answer:

1 ) The modern periodic table lists the elements in order of increasing atomic number (the number of protons in the nucleus of an atom). ... This was mainly because the idea of atoms being made up of smaller sub-atomic particles (protons, neutrons and electrons) had not been developed

2 ) How do you write the mass number?

Another way to refer to a specific atom is to write the mass number of the atom after the name, separated by a hyphen. Symbol-mass format for the above atom would be written as Cr-52. In this notation, the atomic number is not included

ii) The neutron number, symbol N, is the number of neutrons in a nuclide. Atomic number (proton number) plus neutron number equals mass number: Z + N = A. The difference between the neutron number and the atomic number is known as the neutron excess: D = N - Z = A - 2Z.

3 ) Cathode rays come from the cathode, because the cathode is charged negatively. So those rays strike and ionize the gas sample inside the container. The electrons that were ejected from gas ionization travel to the anode. These rays are electrons that are actually produced from the gas ionization inside the tube.

4 ) : one of the stable states of constant energy that may be assumed by a physical system —used especially of the quantum states of electrons in atoms and of nuclei.

5 ) Are anode rays produced from anode?

These were also called anode rays because they move from the anode. It was found that the anode rays consist of positively charged particles. Therefore, these rays were also called positive rays

Answer 2

Answer:

1 • The development of various atomic models and advances in quantum theory revealed that the atomic number is the most basic property of a chemical element. This led to the modification of Mendeleev's periodic law, which is today called as modern periodic law.

2• a) 35.453

b)18

3• The stream of electrons in cathode ray tube constitutes the cathode rays. Electrons are emitted by hot filament by the process of thermionic emission. These electrons pass through controlling and focusing device . They are accelerated by applying appropriate voltage between cathode and anode and finally made incident on a flourascent screen after passing through cross electric and magnetic fields

4• Energy levels (also called electron shells) are fixed distances from the nucleus of an atom where electrons may be found.