What are the characteristics of the particles of matter?
Mass and Volume,, Continuous motion, State variability, Energy levels
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A diver is able to cut through water in a swimming pool. Which property of matter does this observation show?
Fluidity refers to the ability of a substance to flow and change shape when subjected to an external force. Liquids, such as water in this case, exhibit fluidity because their particles can move past each other relatively easily while still maintaining some cohesive forces.
Give reasons: hot sizzling food reaches several metres away, but for cold food you have to go close.
The smell of hot sizzling food travels several meters due to the high kinetic energy and rate of diffusion of its volatile particles (शीघ्र वाष्प रूप हो जाने वाला).
Which of the following are matter? Chair, air, love, smell, hate, almonds, thought, cold, lemon water, smell of perfume.
Matter is anything that has mass and takes up space. Based on this definition, the items that are matter in the given list are: Chair, air, almonds, cold, lemon water, and smell of perfume. The rest (love, smell, hate, thought) are abstract concepts and do not have mass or occupy space in the same way that physical objects do.
If Z = 3, what would be the valency of the element? Also, name the element.
The atomic number (Z) represents the number of protons in the nucleus, which equals the number of electrons in a neutral atom. In Lithium’s case, with Z = 3, it has 3 protons and 3 electrons.
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The average atomic mass of a sample of an element X is 16.2 u. What are the percentages of isotopes 168X and 188X in the sample?
The sample of element X is composed of 90% 168X and 10% 188X isotopes.
If bromine atom is available in the form of, say, two isotopes 7935Br (49.7%) and 8135Br (50.3%), calculate the average atomic mass of bromine atom.
If bromine atom is available in the form of two isotopes 79 35Br (49.7%) and 81 35Br (50.3%), calculate the average atomic mass of bromine atom. Thus, the average atomic mass of bromine is 80u.
Summarise the rules for writing of distribution of electrons in various shells for the first eighteen elements.
Electrons fill the lowest energy levels or shells first before occupying higher energy levels.
The maximum number of electrons in a shell is given by the formula 2n², where ‘n’ is the principal quantum number of that shell.
The electron distribution for the first eighteen elements follows the pattern: 2, 8, 8 for the first, second, and third energy levels (or shells) respectively.
Compare all the proposed models of an atom given in this chapter.
Dalton’s model proposed that atoms were indivisible and identical spheres.
Thomson’s model, also known as the “plum pudding” model or the “raisin bun” model, proposed that atoms consist of a positively charged sphere with negatively charged electrons embedded within it, much like raisins in a pudding or plums in a bun.
Rutherford’s model arose from the famous gold foil experiment.
Bohr’s model built upon Rutherford’s nuclear model but introduced the concept of quantized electron orbits.
Compare all the proposed models of an atom given in this chapter. Read More »
What are the limitations of Rutherford’s model of the atom?
Electron orbits: It didn’t specify how electrons moved around the nucleus. Classical physics predicted they would lose energy and spiral into the nucleus.
Light emission: It couldn’t explain how atoms emit specific frequencies of light.
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What are the limitations of J.J. Thomson’s model of the atom?
► It couldn’t explain how negatively charged electrons were held within a positively charged sphere. According to electrostatics, they should repel each other.
► It didn’t explain about the positively charged nucleus in the center of the atom.
► The model couldn’t explain the results of Ernest Rutherford’s gold foil experiment, where some alpha particles deflected significantly, indicating a very small, dense core
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Compare the properties of electrons, protons and neutrons.
Property Electron Proton Neutron Charge Negative (-1) Positive (+1) No charge (neutral) Mass Very small (9.1 x 10^-31 kg) Relatively heavy (1.67 x 10^-27 kg) Similar to proton (1.67 x 10^-27 kg) Location in Atom Outside the nucleus, in orbitals Inside the nucleus Inside the nucleus More Exercises Questions 2. What are the limitations of J.J. Thomson’s model
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