Question:
Describe Bohr’s model of the atom.
Answer:
In 1913, Neil Bohr overcame the limitations of Rutherford model and proposed a model model of atomic structure. It has the following postulates:
- Electrons revolve around the nucleus in a limited number of orbits called permissible or discrete orbits.
- These discrete orbits have definite energy hence they are called energy levels or energy shells. These orbits or shells are represented by the letters K,L,M,N,… or the numbers, n=1,2,3,4,…
- The energy of an electron remains constant so long as it stays in the given energy level. It means electrons present in different orbits have different energies.
- When an electron jumps from lower energy level to higher energy level, some energy is absorbed. While some amount of energy is released when an electron jumps from higher energy level to lower one.
Structure of the Atom
Q 1.
Compare an electron, a proton and a neutron in respect of their relative masses and charges.
Q 2.
What do you think would be the observation if the ?-particle scattering experiment is carried out using a foil of a metal other than gold?
Q 3.
Fill in the blanks :
Anode rays are also called ___________.
Q 4.
Who discovered protons?
Q 5.
Fill in the blanks :
In the three fundamental sub-atomic particles, _________ are negatively charged, _________ are positively charged and ____________ have no charges.
Q 6.
What is the relationship between an atom containing 11 protons, 11 electrons and 11 neutrons, and another atom containing 11 protons, 11 electrons and 12 neutrons ?
Q 7.
Describe briefly Thomson's model of an atom.
Q 8.
What is the absolute mass and charge of a proton ?
Q 9.
How many times is a proton heavier than an electron ?
Q 10.
On the basis of Rutherford’s model of an atom, which subatomic particle is present in the nucleus of an atom?
Q 11.
What is the maximum number of electrons which can be accommodated in the L shell of an atom
Q 12.
What is mass number?
Q 13.
What is ionization energy?
Q 14.
Give one use each of the following radioactive isotopes :
(a)Uranium-235 (b) Cobalt-60
Q 15.
State the number of electrons present in the outermost shell of the atoms of the following elements :
(i) Neon(ii)Chlorine
Q 16.
If an atom contains one electron and one proton, will it carry any charge or not?
Q 17.
What is the maximum number of electrons an M shell of the atom can accommodate ?
Q 18.
What is a neutron ? State its relative mass and charge.
Q 19.
Fill in the blanks :
Atoms are made up of __________, ___________ and __________.
Q 20.
Write a short note on Nucleus.
Q 21.
Fill in the blanks :
______ are atoms of the same element, which have same number of protons but different mass numbers.
Q 22.
Name the radioactive isotope which is used in the treatment of cancer.
Q 23.
Fill in the blanks :
Atomic number is equal to _____________.
Q 24.
Fill in the blanks :
The maximum number of electrons that can be accommodated in L-shell are _______.
Q 25.
What is the maximum number of electrons that can go into the N shell of an atom ?
Q 26.
State one use of radioactive isotopes in medicine.
Q 27.
What name is given to those isotopes which have unstable nuclei and emit various types of radiations ?
Q 28.
Fill in the blanks :
The fundamental particle not present in hydrogen atom is __________.
Q 29.
Fill in the blanks :
Nucleons are __________ and ___________.
Q 30.
Which shell of an atom can accommodate a maximum of
(a) 8 electrons?
Q 31.
How does an electron differ from a neutron ?
Q 32.
(a) Describe Bohr's model of the atom. How did Neils Bohr explain the stability of atom ?
(b) An element has an atomic number of 11 and its mass number is 23. What is the arrangement of electrons in the shells ? State nuclear composition of an atom of the element.
Q 33.
State one use of radioactive isotopes in industry.
Q 34.
Fill in the blanks :
The _________ of an atom is dense, small in size and is positively charged.
Q 35.
Fill in the blanks :
The mass number of an atom is equal to the number of ________ in its nucleus.
Q 36.
What is the maximum number of electrons which can be accommodated in the K shell of an atom
Q 37.
Name the particles which actually determine the mass of an atom.
Q 38.
What do you understand by the term 'electronic configuration' of an element ? Write down the electron configuration of oxygen (At. No. = 8).
Q 39.
What is a proton ? How does it differ from a neutron ?
Q 40.
What name is given to those atoms which contain the same number of protons and electrons but different number of neutrons ?
Q 41.
(a)What are valence electrons ? Where are valence electrons situated in an atom ?
(b)What is the number of valence electrons in the atoms of an element having atomic number 13 ? Name the Valency shell of this atom.
Q 42.
Name the fundamental particle not present in the nucleus of hydrogen atom
Q 43.
What were the observations of Rutherford's ?-scattering experiment?
Q 44.
What were the important features of atomic model based on Rutherford's scattering experiment?
Q 45.
Fill in the blanks :
________ rays are negatively charged.
Q 46.
Fill in the blanks :
Rutherford's scattering experiment is related to to the size of ____________.
Q 47.
Fill in the blanks :
Co-60 a radio isotope is used in treatment of __________.
Q 48.
What is the electronic configuration of a hydrogen atom
Q 49.
State the location of electrons, protons and neutrons in an atom.
Q 50.
Fill in the following blanks
Atomic
number | Mass number | Protons | Neutrons | Electrons | Symbol |
|---|
| 10 | 22 | ....... | ........ | ....... | ........ |
