EASY
9th CBSE
IMPORTANT
Earn 100
Neutron is present in all atoms
(i) Protium (ii) Deuterium (iii) Tritium (iv) Helium
50% studentsanswered this correctly
Important Questions on Structure of Atom
EASY
9th CBSE
IMPORTANT
Isobars differ in number of
(i) Protons (ii) Electrons (iii) Neutrons (iv) Nucleons
EASY
9th CBSE
IMPORTANT
Which of the following isotopes are not used in the treatment of cancer?
(i) P - 32 (ii) I - 131 (iii) Co - 60 (iv) U - 235
EASY
9th CBSE
IMPORTANT
The valency of which of the following elements is not zero?
(i) Hydrogen (ii) Helium (iii) Gold (iv) Silver
MEDIUM
9th CBSE
IMPORTANT
Which of the following are true for an element?
(i) Atomic number = number of protons + number of electrons
(ii) Mass number = number of protons + number of neutrons
(iii) Atomic mass = number of protons + number of neutrons
(iv) Atomic number = number of protons + number of electrons
MEDIUM
9th CBSE
IMPORTANT
| Column I | Column II |
|---|---|
| A. Ernest Rutherford | (i) Indivisibility of Atoms |
| B. J J Thomson | (ii) Stationary orbits |
| C. Dalton | (iii) Concept of nucleus |
| D. Neil Bohr | (iv) Discovery of electrons |
MEDIUM
9th CBSE
IMPORTANT
| Column I | Column II |
|---|---|
| A. Nucleus | (i) Particle carries one unit positively charge |
| B. Electron | (ii) Small heavy positively charged body |
| C. Proton | (iii) Particle carries one unit negative charge |
| D. Neutron | (iv) Particles which are neutral |
MEDIUM
9th CBSE
IMPORTANT
| Column I | Column II |
|---|---|
| A. Cations | (i) Atoms formed by gain of electrons |
| B. Anions | (ii) Treatment for thyroid disorder |
| C. Iodine - 131 | (iii) Used as a nuclear fuel |
| D. Uranium - 235 | (iv) Formed from atoms by loss of electrons |
EASY
9th CBSE
IMPORTANT
As per Thomson's model of the atom, an atom has both negative and positive charges which are equal in number and magnitude. So, they balance each other as a result of which atom as a whole is electrically neutral. On the basis of Rutherford's model of an atom, protons are present in the nucleus of an atom. If α - particle scattering experiment is carried out using a foil of any metal as thin as gold foil used by Rutherford, there would be no change in observations. But since other metals are not so malleable so, such a thin foil is difficult to obtain. If we use a thick foil, then more α - particles would bounce back and no idea about the location of positive mass in the atom would be available with such a certainty. The three sub - atomic particles of an atom are protons, electrons and neutrons. An electron is a negatively charged particle, whereas a proton is a positively charged particle. The magnitude of their charges is equal. Therefore, an atom containing one electron and one proton will not carry any charge. Thus, it will be a neutral atom. If the number of electrons in the outermost shell of the atom of an element is less than or equal to 4, then the valency of the element is equal to the number of electrons in the outer most shell. On the other hand, if the number of electrons in the outermost shell of the atom of an element is greater than4, then the valency of that element is determined by subtracting the number of electrons in the outermost shell from 8. The distribution of electrons in chlorine, sulphur, and magnesium atoms are 2, 8, 7; 2, 8, 6 and 2, 8, 2 respectively. The valency of an element is the combining capacity of that element. The valency of an element is determined by the number of valence electrons present in the atom of that element
What will be the valency of the element in the outermost shell of the atom of an element is less than or equal to 4?
