Thomson's model: An atom consists of a positively charged sphere with electrons embedded in it. Rutherford's model: • An atom consists of a positively charged particles concentrated at the center known as the nucleus. • The size of the nucleus is very small as compared to the size of the atom. • TheRead more
Thomson’s model: An atom consists of a positively charged sphere with electrons embedded in it.
Rutherford’s model:
• An atom consists of a positively charged particles concentrated at the center known as the nucleus.
• The size of the nucleus is very small as compared to the size of the atom.
• The electron revolve around the nucleus in well – defined orbits.
Bohr’s model:
• There are only certain orbits know as discrete orbits inside the atom in which electrons revolve around the nucleus. Electrons do not radiate energy while revolving.
Bohr’s model of the atom Niels Bohr proposed the following postulates regarding the model of the atom. (i) Only certain orbits known as discrete orbits of electrons are allowed inside the atom. (ii) While revolving in these discrete orbits, the electrons do not radiate energy. The first orbit (i.e.,Read more
Bohr’s model of the atom Niels Bohr proposed the following postulates regarding the model of the atom.
(i) Only certain orbits known as discrete orbits of electrons are allowed inside the atom.
(ii) While revolving in these discrete orbits, the electrons do not radiate energy.
The first orbit (i.e., for n = 1) is represented by letter K. Similarly, for n = 2, it is L − shell, for n = 3, it is M − shell and for n = 4, it is N − shell. These orbits or shells are also called energy levels.
According to Rutherford’s model of an atom, electrons revolve around the nucleus in fixed orbits. But, an electron revolving in circular orbits will not be stable because during revolution, it will experience acceleration. Due to acceleration, the electrons will lose energy in the form of radiationRead more
According to Rutherford’s model of an atom, electrons revolve around the nucleus in fixed orbits. But, an electron revolving in circular orbits will not be stable because during revolution, it will experience acceleration. Due to acceleration, the electrons will lose energy in the form of radiation and fall into the nucleus. In such a case, the atom would be highly unstable and collapse.
According to J.J. Thomson’s model of an atom, an atom consists of a positively charged sphere with electrons embedded in it. However, it was later found that the positively charged particles reside at the center of the atom called the nucleus, and the electrons revolve around the nucleus. For more aRead more
According to J.J. Thomson’s model of an atom, an atom consists of a positively charged sphere with electrons embedded in it. However, it was later found that the positively charged particles reside at the center of the atom called the nucleus, and the electrons revolve around the nucleus.
Electron: (i) Electron are present outside the nucleus of an atom. (ii) Electron are negatively charged. (iii) The mass of an electron is considered to negligible. Proton: (i) Proton are present in the nucleus of an atom. (ii) Proton are positively charged. (iii) The mass of a proton is approximatelRead more
Electron:
(i) Electron are present outside the nucleus of an atom.
(ii) Electron are negatively charged.
(iii) The mass of an electron is considered to negligible.
Proton:
(i) Proton are present in the nucleus of an atom.
(ii) Proton are positively charged.
(iii) The mass of a proton is approximately 2000 times as the mass of an electron.
Neutron:
(i) Neutron are present in the nucleus of an atom.
(ii) Neutron are neutral.
(iii) The mass of neutron is nearly equal to the mass of a proton.
Atomic mass of Na = 23u (Given) Then, gram atomic mass of Na = 23g Now, 23g of Na contains = 6.022×10²³ number of atoms Thus, 100g of Na contains = 6.022×10²³ ×100/23 number of atoms = 2.6182 × 10²⁴ number of atoms Again, atomic mass of Fe = 56u (Given) Then, gram atomic mass of Fe = 56g Now, 56 g oRead more
Atomic mass of Na = 23u (Given)
Then, gram atomic mass of Na = 23g
Now, 23g of Na contains = 6.022×10²³ number of atoms
Thus, 100g of Na contains = 6.022×10²³ ×100/23 number of atoms
= 2.6182 × 10²⁴ number of atoms
Again, atomic mass of Fe = 56u (Given)
Then, gram atomic mass of Fe = 56g
Now, 56 g of Fe contains = 6.022×10²³ number of atoms
Thus, 100 g of Fe
6.022×10²³ ×100/56 number of atoms
= 1.0753 × 10²⁴number of atoms
Therefore, 100 grams of sodium contain more number of atoms than 100 grams of iron.
One mole of carbon atoms weighs 12g (Given) i.e., mass of 1 mole of carbon atoms = 12g Then, mass of 6.022× 10²³ number of carbon atoms = 12g Therefore, mass of 1 atom of carbon = 12/6.022×10²³ g = 1.9926 × 10⁻²³ g For more answers visit to website: https://www.tiwariacademy.com/ncert-solutions/clasRead more
One mole of carbon atoms weighs 12g (Given)
i.e., mass of 1 mole of carbon atoms = 12g
Then, mass of 6.022× 10²³ number of carbon atoms = 12g
Therefore, mass of 1 atom of carbon = 12/6.022×10²³ g
= 1.9926 × 10⁻²³ g
Formula unit mass of ZnO = Atomic mass of Zn + Atomic mass of O = 65 + 16 = 81u Formula unit mass of Na₂O = 2 × Atomic mass of Na + Atomic mass of O = 2 × 23 + 16 = 62u Formula unit mass of K₂CO₃ = 2 × Atomic mass of K + Atomic mass of C + 3 × Atomic mass of O = 2 × 39 + 12 + 3 × 16 = 138u For moreRead more
Formula unit mass of ZnO = Atomic mass of Zn + Atomic mass of O
= 65 + 16 = 81u
Formula unit mass of Na₂O = 2 × Atomic mass of Na + Atomic mass of O
= 2 × 23 + 16 = 62u
Formula unit mass of K₂CO₃
= 2 × Atomic mass of K + Atomic mass of C + 3 × Atomic mass of O
= 2 × 39 + 12 + 3 × 16 = 138u
Molecular mass of H₂ = 2 × Atomic mass of H = 2 × 1 = 2u Molecular mass of O₂ = 2 × Atomic mass of O = 2 × 16 = 32u Molecular mass of Cl₂ = 2 × Atomic mass of Cl = 2 × 35.5 = 71u Molecular mass of CO₂ = Atomic mass of C + 2 × Atomic mass of O = 12 + 2 × 16 = 44u Molecular mass of CH₄ = Atomic mass oRead more
Molecular mass of H₂ = 2 × Atomic mass of H
= 2 × 1 = 2u
Molecular mass of O₂ = 2 × Atomic mass of O
= 2 × 16 = 32u
Molecular mass of Cl₂ = 2 × Atomic mass of Cl
= 2 × 35.5 = 71u
Molecular mass of CO₂ = Atomic mass of C + 2 × Atomic mass of O
= 12 + 2 × 16 = 44u
Molecular mass of CH₄ = Atomic mass of C + 4 × Atomic mass of H
= 12 + 4 × 1 = 16u
Molecular mass of C₂H₆ = 2 × Atomic mass of C + 6 × Atomic mass of H
= 2 × 12 + 6 × 1 = 30u
Molecular mass of C₂H₄ = 2 × Atomic mass of C + 4 × Atomic mass of H
= 2 × 12 + 4 × 1 = 28u
Molecular mass of NH₃ = Atomic mass of N + 3 × Atomic mass of H
= 14 + 3 × 1 =17u
Molecular mass of CH₃OH Atomic mass of C+4 ×Atomic mass of H+Atomic mass of O
= 12 + 4 × 1 + 16 = 32u
(i) In an H₂S molecule, three atoms are present; two of hydrogen and one of sulphur. (ii) In a PO₄₃- ion, five atoms are present; one of phosphorus and four of oxygen. For more answers visit to website: https://www.tiwariacademy.com/ncert-solutions/class-9/science/chapter-3/
(i) In an H₂S molecule, three atoms are present; two of hydrogen and one of sulphur.
(ii) In a PO₄₃- ion, five atoms are present; one of phosphorus and four of oxygen.
Compare all the proposed models of an atom given in this chapter.
Thomson's model: An atom consists of a positively charged sphere with electrons embedded in it. Rutherford's model: • An atom consists of a positively charged particles concentrated at the center known as the nucleus. • The size of the nucleus is very small as compared to the size of the atom. • TheRead more
Thomson’s model: An atom consists of a positively charged sphere with electrons embedded in it.
Rutherford’s model:
• An atom consists of a positively charged particles concentrated at the center known as the nucleus.
• The size of the nucleus is very small as compared to the size of the atom.
• The electron revolve around the nucleus in well – defined orbits.
Bohr’s model:
• There are only certain orbits know as discrete orbits inside the atom in which electrons revolve around the nucleus. Electrons do not radiate energy while revolving.
For more answers visit to website:
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Describe Bohr’s model of the atom.
Bohr’s model of the atom Niels Bohr proposed the following postulates regarding the model of the atom. (i) Only certain orbits known as discrete orbits of electrons are allowed inside the atom. (ii) While revolving in these discrete orbits, the electrons do not radiate energy. The first orbit (i.e.,Read more
Bohr’s model of the atom Niels Bohr proposed the following postulates regarding the model of the atom.
(i) Only certain orbits known as discrete orbits of electrons are allowed inside the atom.
(ii) While revolving in these discrete orbits, the electrons do not radiate energy.
The first orbit (i.e., for n = 1) is represented by letter K. Similarly, for n = 2, it is L − shell, for n = 3, it is M − shell and for n = 4, it is N − shell. These orbits or shells are also called energy levels.
For more answers visit to website:
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What are the limitations of Rutherford’s model of the atom?
According to Rutherford’s model of an atom, electrons revolve around the nucleus in fixed orbits. But, an electron revolving in circular orbits will not be stable because during revolution, it will experience acceleration. Due to acceleration, the electrons will lose energy in the form of radiationRead more
According to Rutherford’s model of an atom, electrons revolve around the nucleus in fixed orbits. But, an electron revolving in circular orbits will not be stable because during revolution, it will experience acceleration. Due to acceleration, the electrons will lose energy in the form of radiation and fall into the nucleus. In such a case, the atom would be highly unstable and collapse.
For more answers visit to website:
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What are the limitations of J.J. Thomson’s model of the atom?
According to J.J. Thomson’s model of an atom, an atom consists of a positively charged sphere with electrons embedded in it. However, it was later found that the positively charged particles reside at the center of the atom called the nucleus, and the electrons revolve around the nucleus. For more aRead more
According to J.J. Thomson’s model of an atom, an atom consists of a positively charged sphere with electrons embedded in it. However, it was later found that the positively charged particles reside at the center of the atom called the nucleus, and the electrons revolve around the nucleus.
For more answers visit to website:
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Compare the properties of electrons, protons and neutrons.
Electron: (i) Electron are present outside the nucleus of an atom. (ii) Electron are negatively charged. (iii) The mass of an electron is considered to negligible. Proton: (i) Proton are present in the nucleus of an atom. (ii) Proton are positively charged. (iii) The mass of a proton is approximatelRead more
Electron:
(i) Electron are present outside the nucleus of an atom.
(ii) Electron are negatively charged.
(iii) The mass of an electron is considered to negligible.
Proton:
(i) Proton are present in the nucleus of an atom.
(ii) Proton are positively charged.
(iii) The mass of a proton is approximately 2000 times as the mass of an electron.
Neutron:
(i) Neutron are present in the nucleus of an atom.
(ii) Neutron are neutral.
(iii) The mass of neutron is nearly equal to the mass of a proton.
For more answers visit to website:
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Which has more number of atoms, 100 grams of sodium or 100 grams of iron (given, atomic mass of Na = 23 u, Fe = 56 u)?
Atomic mass of Na = 23u (Given) Then, gram atomic mass of Na = 23g Now, 23g of Na contains = 6.022×10²³ number of atoms Thus, 100g of Na contains = 6.022×10²³ ×100/23 number of atoms = 2.6182 × 10²⁴ number of atoms Again, atomic mass of Fe = 56u (Given) Then, gram atomic mass of Fe = 56g Now, 56 g oRead more
Atomic mass of Na = 23u (Given)
Then, gram atomic mass of Na = 23g
Now, 23g of Na contains = 6.022×10²³ number of atoms
Thus, 100g of Na contains = 6.022×10²³ ×100/23 number of atoms
= 2.6182 × 10²⁴ number of atoms
Again, atomic mass of Fe = 56u (Given)
Then, gram atomic mass of Fe = 56g
Now, 56 g of Fe contains = 6.022×10²³ number of atoms
Thus, 100 g of Fe
6.022×10²³ ×100/56 number of atoms
= 1.0753 × 10²⁴number of atoms
Therefore, 100 grams of sodium contain more number of atoms than 100 grams of iron.
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If one mole of carbon atoms weighs 12 grams, what is the mass (in gram) of 1 atom of carbon?
One mole of carbon atoms weighs 12g (Given) i.e., mass of 1 mole of carbon atoms = 12g Then, mass of 6.022× 10²³ number of carbon atoms = 12g Therefore, mass of 1 atom of carbon = 12/6.022×10²³ g = 1.9926 × 10⁻²³ g For more answers visit to website: https://www.tiwariacademy.com/ncert-solutions/clasRead more
One mole of carbon atoms weighs 12g (Given)
i.e., mass of 1 mole of carbon atoms = 12g
Then, mass of 6.022× 10²³ number of carbon atoms = 12g
Therefore, mass of 1 atom of carbon = 12/6.022×10²³ g
= 1.9926 × 10⁻²³ g
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Calculate the formula unit masses of ZnO, Na₂O, K₂CO₃, given atomic masses of Zn = 65 u, Na = 23 u, K = 39 u, C = 12 u, and O = 16 u.
Formula unit mass of ZnO = Atomic mass of Zn + Atomic mass of O = 65 + 16 = 81u Formula unit mass of Na₂O = 2 × Atomic mass of Na + Atomic mass of O = 2 × 23 + 16 = 62u Formula unit mass of K₂CO₃ = 2 × Atomic mass of K + Atomic mass of C + 3 × Atomic mass of O = 2 × 39 + 12 + 3 × 16 = 138u For moreRead more
Formula unit mass of ZnO = Atomic mass of Zn + Atomic mass of O
= 65 + 16 = 81u
Formula unit mass of Na₂O = 2 × Atomic mass of Na + Atomic mass of O
= 2 × 23 + 16 = 62u
Formula unit mass of K₂CO₃
= 2 × Atomic mass of K + Atomic mass of C + 3 × Atomic mass of O
= 2 × 39 + 12 + 3 × 16 = 138u
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Calculate the molecular masses of : H₂, O₂, Cl₂, CO₂, CH₄, C₂H₆, C₂H₄, NH₃, CH₃OH.
Molecular mass of H₂ = 2 × Atomic mass of H = 2 × 1 = 2u Molecular mass of O₂ = 2 × Atomic mass of O = 2 × 16 = 32u Molecular mass of Cl₂ = 2 × Atomic mass of Cl = 2 × 35.5 = 71u Molecular mass of CO₂ = Atomic mass of C + 2 × Atomic mass of O = 12 + 2 × 16 = 44u Molecular mass of CH₄ = Atomic mass oRead more
Molecular mass of H₂ = 2 × Atomic mass of H
= 2 × 1 = 2u
Molecular mass of O₂ = 2 × Atomic mass of O
= 2 × 16 = 32u
Molecular mass of Cl₂ = 2 × Atomic mass of Cl
= 2 × 35.5 = 71u
Molecular mass of CO₂ = Atomic mass of C + 2 × Atomic mass of O
= 12 + 2 × 16 = 44u
Molecular mass of CH₄ = Atomic mass of C + 4 × Atomic mass of H
= 12 + 4 × 1 = 16u
Molecular mass of C₂H₆ = 2 × Atomic mass of C + 6 × Atomic mass of H
= 2 × 12 + 6 × 1 = 30u
Molecular mass of C₂H₄ = 2 × Atomic mass of C + 4 × Atomic mass of H
= 2 × 12 + 4 × 1 = 28u
Molecular mass of NH₃ = Atomic mass of N + 3 × Atomic mass of H
= 14 + 3 × 1 =17u
Molecular mass of CH₃OH Atomic mass of C+4 ×Atomic mass of H+Atomic mass of O
= 12 + 4 × 1 + 16 = 32u
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How many atoms are present in a (i) H₂S molecule and (ii) PO₄³⁻ ion?
(i) In an H₂S molecule, three atoms are present; two of hydrogen and one of sulphur. (ii) In a PO₄₃- ion, five atoms are present; one of phosphorus and four of oxygen. For more answers visit to website: https://www.tiwariacademy.com/ncert-solutions/class-9/science/chapter-3/
(i) In an H₂S molecule, three atoms are present; two of hydrogen and one of sulphur.
(ii) In a PO₄₃- ion, five atoms are present; one of phosphorus and four of oxygen.
For more answers visit to website:
See lesshttps://www.tiwariacademy.com/ncert-solutions/class-9/science/chapter-3/