Important questions and Answer of Chapter Journey inside an atoms
- Charge of electron
Ans- (–1.602 × 10–19 C)
2. Who discovered electron
Ans- J.J ThomsonDefine subatomic particle
Ans- electrons, protons, and neutrons.
3. Define plum pudding model
Ans- Thomson proposed the atom to be a sphere of positive charge with electrons distributed throughout it. This model was compared to a pudding with plums embedded in it, called the plum pudding model.
watermelon , where the red pulp represents the positively charged matter, and the seeds represent electrons distributed throughout the atom.
4. Define gold foil experiment or α-ray scattering experiment.
Ans- According to Thomson’s model, the positive charge in the atom was spread out evenly. So they expected the alpha particles to pass straight through the gold foil or be deflected only slightly. But to their surprise, while most particles passed through undeflected, some were sharply deflected (Fig. 8.4), and a few even bounced back. This deflection from the straight path is called scattering. Hence, the gold foil experiment is also called an α-ray scattering experiment
5. Limitation of Thomson model
Ans- Thomson’s model failed to explain the results of the gold foil experiment, particularly the deflection of some α-particles through large angles and that most of the α-particles passed undeflected
6. Define Rutherford’s model of an atom
Ans- Most of an atom is empty space, as most α-particles passed through the gold foil without any deflection.
The nucleus is dense, contains all the positive charge and most of the mass of an atom.
The electrons revolve around the nucleus, somewhat like planets orbiting the Sun. Hence, this model is called the planetary model of the atom
7. Limitation of Rutherford’s model
Ans- a particle moving in a circular path is constantly changing direction, which means it is accelerating. If a negatively charged electron keeps accelerating around the nucleus, it should lose energy. Losing energy would make it spiral inward and eventually fall into the positively charged nucleus (Fig. 8.6). If that really happened, atoms would collapse and would not exist! But in reality, atoms are stable , This meant that Rutherford’s model was not completely correct
8. Who discovered proton
Ans- Rutherford
9. Define Bohr’s model of the atom
Ans- Electrons do not move randomly around the nucleus but follow fixed circular paths called stationary states, orbits, or shells. In each shell, an electron has a definite amount of energy, so these shells are also called energy levels.
These shells are represented by the letters K, L, M, N, … or by the numbers n = 1, 2, 3, 4, …
The energy of these levels increases as we move away from the nucleus. That is, the energy of an electron in the L-shell (n = 2) is more than that of an electron in the K-shell (n = 1). The farther away a shell is from the nucleus, the higher is its energy.
An electron can move to another shell by absorbing or releasing a fixed amount of energy equal to the difference between the energies of the two levels. y Each shell can hold only a certain number of electrons.
In a stationary state, the energy of an electron remains constant, even though it is in motion around the nucleus.
10. Who discovered Neutron
Ans- James Chadwick
11. Define Atomic Number
Ans- The number of protons in the nucleus of an atom of an element is known as its atomic number. It is designated by the symbol Z, For example, hydrogen has one proton and one electron, so its atomic number is 1. Helium, with atomic number 2, has 2 protons and 2 electrons.
12. Define Mass Number
Ans- The total number of protons and neutrons present in the nucleus of an atom is called its mass number, and is denoted by A.
13. Define electronic configuration of the atom
Ans- The distribution of electrons among various shells is known as the electronic configuration of the atom
14. Define Combining capacity
Ans- The number of atoms of hydrogen or chlorine with which one atom of an element can combine to form a compound is called its combining capacity. It is expressed in terms of hydrogen and chlorine because both possess a combining capacity of one. For example, in H2 O (water)
15. Define valence shell.
Ans- The outermost shell containing electrons of an atom is known as its valence shell.
16. Define valence electrons.
Ans- The electrons present in outermost shell are known as valence electrons.
17. Define valency of the element
Ans- The number of electrons gained, lost, or shared to complete the octet is called the valency of the element
18. Define isotopes.
Ans- atoms of the same element that could have the same number of protons (atomic number, Z) yet could have different numbers of neutrons, and thus, different mass numbers are called isotopes
19. Define isobars.
Ans- When atoms of different elements have the same mass number, but different atomic numbers, they are called isobars.
20. Define Average atomic mass
Ans- The average atomic mass of an element is calculated based on the relative abundance of its isotopes in nature.