{"id":28879,"date":"2023-03-08T12:59:42","date_gmt":"2023-03-08T07:29:42","guid":{"rendered":"https:\/\/icsesolutions.com\/?p=28879"},"modified":"2023-03-09T10:20:15","modified_gmt":"2023-03-09T04:50:15","slug":"new-simplified-chemistry-class-9-icse-solutions-atomic-structure","status":"publish","type":"post","link":"https:\/\/icsesolutions.com\/new-simplified-chemistry-class-9-icse-solutions-atomic-structure\/","title":{"rendered":"New Simplified Chemistry Class 9 ICSE Solutions Atomic Structure"},"content":{"rendered":"
ICSE Solutions<\/a>Selina ICSE Solutions<\/a>ML Aggarwal Solutions<\/a><\/p>\n Viraf J Dalal Chemistry Class 9 Solutions and Answers<\/strong><\/p>\n Simplified Chemistry<\/a>Physics<\/a>Chemistry<\/a>Biology<\/a>Maths<\/a>Geography<\/a>HistoryCivics<\/a><\/p>\n Exercise Question 1.(1984)<\/strong><\/span> Question 1.(1985)<\/strong><\/span> <\/p>\n Question 1.(1986)<\/strong><\/span> Question 2.(1986)<\/strong><\/span> Question 1.(1987)<\/strong><\/span> Answer: Question 2.(1987)<\/strong><\/span> Answer:<\/strong><\/span><\/p>\n Question 1.(1988) <\/p>\n Answer:<\/strong><\/span> Question 1.(1989)<\/strong><\/span> Answer:<\/strong><\/span> Question 2.(1989)<\/strong><\/span> Question 1.(1990)<\/strong><\/span> (a)<\/strong> electrons in the different orbits or shells in one atom of aluminium. Question 2.(1990)<\/strong><\/span> Question 3.(1990)<\/strong><\/span> Answer: Question 4.(1990)<\/strong><\/span> Question 1.(1991)<\/strong><\/span> Question 1.(1992)<\/strong><\/span> Question 1.(1993)<\/strong><\/span> Question 2.(1993)<\/strong><\/span> Answer:<\/strong><\/span><\/p>\n Question 1.(1994)<\/strong><\/span> Question 2.(1994)<\/strong><\/span> Question 3.(1994)<\/strong><\/span> Question 4.(1994)<\/strong><\/span> Question 5.(1994)<\/strong><\/span> Answer:<\/strong><\/span> Additional Questions<\/strong><\/span><\/p>\n Question 1.<\/strong><\/span> Contradiction by Modern Theory :<\/strong><\/p>\n Question 2.<\/strong><\/span> Answer:<\/strong><\/span> He found that when an electric discharge is passed through a tube containing a gas at low pressure (0.01 mm of Hg).
\n<\/strong><\/span><\/p>\n
\nDefine the terms : atomic number, mass number and electron.
\nAnswer:<\/strong><\/span>
\nAtomic number [Z] : \u201cIs the number of protons in the nucleus of an atom.\u201d
\nOR \u201cIs the number of positive charges in the nucleus of its atom.\u201d
\nOR \u201cIs the number of electrons in the complete atom.\u201d
\nZ = P = e
\nMass number [A] : \u201cIs the total number of protons and neutrons in the atom of an element.\u201d
\nA = P + n
\nElectron [e] : \u201cA sub-atomic particle having a unit negative charge and mass equal to 1\/1837 of that of hydrogen atom, revolve round the nucleus.\u201d [-1<\/sub>e0<\/sup>]<\/p>\n
\nFrom the symbol He for the element helium, write down the mass number and the atomic number of the element.
\nAnswer:<\/strong><\/span><\/p>\n\n
\nSulphur has an atomic number of 16 and a mass number of 32. State the number of protons and neutrons present in the nucleus of sulphur.
\nAnswer:<\/strong><\/span>
\nProtons \u2192 Atomic number = 16 = P
\nNumber of Neutrons = A \u2013 P = 32 \u2013 16 = 16<\/p>\n
\nGive a simple diagram to show the arrangement of the electrons in an atom of sulphur.
\nAnswer:<\/strong><\/span>
\nIn sulphur atom.
\nNumber of electrons = P = e = 16
\n
\n<\/p>\n
\n2412<\/sub>Mg and 2612<\/sub>Mg are symbols of two isotopes of magnesium. Compare the \u2018 atoms of these isotopes with respect to :<\/p>\n\n
\n
\n<\/strong><\/span><\/p>\n
\nChlorine is an element of atomic number 17. It is a mixture of two isotopes having mass number of 35 and 37.<\/p>\n\n
\n
\nAtom :<\/strong> The basic unit of matter is the smallest particle of an element which can take part in a chemical reaction.<\/li>\n
\n35<\/sup>17<\/sub>Cl number of protons = 17 and number neutrons = 35 \u2013 17 = 18
\nNumber of electrons = 17
\n37<\/sup>17<\/sub> Cl number of protons = 17
\nelectrons = 17
\nneutrons = 20 (37 \u2013 17)<\/li>\n
\n<\/strong><\/span>Five atoms are labelled V to Z<\/p>\n\n
\n(i)
\n1. <\/strong>Contains 7 protons
\nZ \u2013 has atomic number of Z = 7
\n2.<\/strong> Has atomic configuration (2, 7)
\nW \u2013 atomic number = of electrons = 9 (2, 7)
\n(ii)<\/strong> X-atomic number 3
\n= number of electron = (2, 1)
\n\u2234 X has valency [1+]
\nY-atomic number = 8
\n= number of electrons = (2, 6)
\n<\/p>\n
\nElements X, Y, Z have atomic numbers 6, 9 and 12 respectively. Which one :<\/p>\n\n
\nAtomic number of
\nX = 6 = number of electrons (2, 4)
\n\u2234 X has 4 electrons in outermost orbit.
\nY = 9 = number of electrons (2, 7)
\n\u2234 Y form anion = negative ion
\nZ = 12 = [2, 8, 2]
\n\u2234 Z forms cation \u2013 positive ion.<\/p>\n
\nOrdinary chlorine gas has two isotopes : 35<\/sup>17<\/sub>Cl and 37<\/sup>17<\/sub>Cl in the ratio of 3 : 1. Calculate the relative atomic mass [atomic weight] of chlorine.
\nAnswer:
\n
\n<\/strong><\/span><\/p>\n
\nThe atom of aluminium is represented by 27<\/sup>Al13<\/sub>. Write down the number of<\/p>\n
\n(b)<\/strong> protons
\n(c)<\/strong> neutrons
\n(d)<\/strong> the arrangement of electrons<\/p>\n
\nAnswer:
\n
\n<\/strong><\/span><\/p>\n
\nName the clement which does not contain any neutrons in its nucleus.
\nAnswer:<\/strong><\/span>
\nElement is [H] Hydrogen.<\/p>\n
\nElements A, B and C have atomic numbers 9, 20 and 10 respectively.<\/p>\n\n
\n
\n<\/strong><\/span><\/p>\n
\nDefine :<\/strong> Proton, Electron, Neutron.
\nAnswer:<\/strong><\/span>
\nProton<\/strong> is subatomic particle found in nucleus of atom having unit positive charge, mass = 1 hydrogen atom.
\nFound in nucleus of atom and number of protons in an atom = number of electrons.
\nElectron =<\/strong> e = is sub atomic particle revolving around the nucleus of atom having
\nunit \u2013 ve charge, mass = 1\/1840 of 1 hydrogen atom and number of electrons = number of protons.
\nNeutrons = n = is sub-atomic particle found in nucleus of atom, having no charge, mass = mass of 1 proton.<\/p>\n
\nWrite down the electronic configuration of the following (i) <\/strong> 27<\/sup>13<\/sub>X, (ii) <\/strong> 35<\/sup>17<\/sub>Y.
\nWrite down the number of electrons in X and neutrons in Y and the formula of the compound formed by X and Y.[XY3]
\n<\/sub>Answer:
\n
\n
\n<\/strong><\/span><\/p>\n
\nAccording to the Dalton\u2019s Atomic Theory, atoms of the same element are identical in all respects. But according to the Modern Atomic Theory, this postulate is proved wrong. Explain.
\nAnswer:<\/strong><\/span>
\nAccording to modern atomic theory atoms of the same element may not be alike in all respect.
\ne.g. isotopes of chlorine 35<\/sup>17<\/sub>Cl and 37<\/sup>17<\/sub> Cl have different atomic masses 35 and 37. This proves Dalton\u2019s Atomic Theory wrong.<\/p>\n
\nWhat are isotopes.
\nAnswer:<\/strong><\/span>
\nIsotopes :<\/strong> \u201cAtoms of the same element having same atomic number, different mass number and similar chemical properties.\u201d
\n<\/p>\n
\nWrite down :<\/strong><\/p>\n\n
\n
\nMass number = 20 + 15 = 35<\/li>\n
\n37 = n + 17
\nNumber of neutrons = n = 37 \u2013 17 = 20<\/li>\n<\/ol>\n
\nWhat is a proton ? What is the significance of the number of protons found in the atoms of each of the different elements.
\nAnswer:<\/strong><\/span>
\nProton :<\/strong> \u201cIs positively charged sub-particle of atom present in nucleus.\u201d
\nProton helps in determining and understanding the structure and behaviour of an atom. Elements are arranged on the bases of number of protons in their respective atoms.<\/p>\n
\nWhat is the relation between the number of protons and the number of electrons in an atom.
\nAnswer:<\/strong><\/span>
\nThe number of protons in an atom is equal to the number of electrons.<\/p>\n
\nWhat would be the reason for an element to have atoms with differing mass numbers.
\nAnswer:<\/strong><\/span>
\nAtoms of same element have different mass number as these isotopes have different physical constants i.e. different physical properties. OR \u201cAtoms have different number of neutrons.\u201d<\/p>\n
\nCopy and complete the following table relating to the atomic structure of some elements :
\n
\nAnswer:
\n
\n<\/strong><\/span><\/p>\n
\nThe electronic structure [configuration] of fluorine can be written as 2, 7. In a similar way give the electronic configuration of :<\/p>\n\n
\nElectronic configuration of :<\/strong><\/p>\n\n
\nState the main postulates of Dalton\u2019s atomic theory. How does the modern atomic theory contradict and correlate with Dalton\u2019s atomic theory.
\nAnswer:<\/strong><\/span>
\nPostulates of Dalton\u2019s Atomic Theory :<\/strong><\/p>\n\n
\n
\nExplain in brief the experimental proofs which led to the discovery of \u2013<\/p>\n\n
\n(i) Electrons :<\/strong> English physicist William Crookes in 1878 discovered the cathode rays
\n<\/p>\n
\nBlue rays were emitted from the negative plate [i.e. cathode]. These rays were called cathode rays and consist of negatively charged particles now called electrons. Electrons are essential part of each and every atom.
\n(ii) Protons :<\/strong> Since atoms are electrically neutral there must be equal positively charged particles in atom. This led to discovery of the protons.<\/p>\n
\nGoldstein discovered protons. He used a perforated disc as cathode and found positively charged rays travelling in opposite direction to cathode rays.
\nThese were protons i.e. positively charged particles, 1837 times heavier than an electron.
\n(iii) Discovery of Atomic Nucleus :<\/strong> Lord Rutherford in 1911 directed alpha particles (4<\/sup>2<\/sub>He) towards gold foil. The deflection of the alpha particles was observed and concluded that there was nucleus at the centre of atom which was positively charged dense very small space (solid) called nucleus.<\/p>\n
\n(iv) Discovery of Neutrons :<\/strong> As atom contains protons and electrons. Atomic mass of electron in negligible.
\n\u2234 An atom of helium which contains 2 protons should have a mass = (2 \u00d7 1) + 0 = 2 a.m.u. But the atomic mass of a helium atom was found to be approximately 4.0 a.m.u. It was therefore proved that, in the nucleus of an atom, there is an other particle called a neutron which has no electrical charge but is almost of an equal mass as the protons.<\/p>\n