{"id":21289,"date":"2022-05-11T20:00:32","date_gmt":"2022-05-11T14:30:32","guid":{"rendered":"https:\/\/cbselibrary.com\/?p=21289"},"modified":"2023-11-10T15:41:23","modified_gmt":"2023-11-10T10:11:23","slug":"selina-concise-chemistry-class-8-icse-solutions-atomic-structure","status":"publish","type":"post","link":"https:\/\/cbselibrary.com\/selina-concise-chemistry-class-8-icse-solutions-atomic-structure\/","title":{"rendered":"Selina Concise Chemistry Class 8 ICSE Solutions – Atomic Structure"},"content":{"rendered":"
ICSE Solutions<\/a>Selina ICSE Solutions<\/a>ML Aggarwal Solutions<\/a><\/p>\n APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 8 Chemistry Chapter 4 Atomic Structure. You can download the Selina Concise Chemistry ICSE Solutions for Class 8 with Free PDF download option. Selina Publishers Concise Chemistry for Class 8 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.<\/p>\n Selina Class 8 Chemistry ICSE Solutions<\/a>Physics<\/a>Biology<\/a>Maths<\/a>Geography<\/a>History & Civics<\/a><\/p>\n Exercise<\/strong><\/span><\/p>\n 1. Fill in the blanks.<\/strong><\/p>\n (a) Dalton said<\/strong> that atoms could not be divided 2. Write \u2018true’ or ‘false’ for the following statements:<\/strong><\/p>\n (a) An atom on the whole has a positive charge. 3. Give the following a suitable word\/phrase.<\/strong><\/p>\n (a) The sub-atomic particle with negative charge and negligible mass. Answer:<\/strong><\/span><\/p>\n (a) Neutron 4. Multiple Choice Questions<\/strong><\/p>\n (a) The outermost shell of an atom is known as<\/strong><\/p>\n (b) The number of valence electrons present in magnesium is<\/strong><\/p>\n (c) The sub atomic particle with negative charge is<\/strong><\/p>\n (d) If the atomic number of an atom is 17 and mass number is 35 then number of neutron will be<\/strong><\/p>\n (e) The number of electrons in an atom is equal to number of<\/strong><\/p>\n (f) The sum of number of protons and number of neutrons present in the nucleus of an atom is called its<\/strong><\/p>\n Question 5.<\/strong><\/span> Question 6.<\/strong><\/span> Question 7.<\/strong><\/span> Question 8.<\/strong><\/span> (b)<\/strong> Rutherford\u2019s atomic model could not explain the stability of the atom as it is like a solar system, the sun is at the centre and the planets revolve around it, in an atom the electrons revolve around the centrally located nucleus containing protons.<\/p>\n Question 9.<\/strong><\/span> Question 10.<\/strong><\/span> Question 11.<\/strong><\/span> Question 12.<\/strong><\/span> Question 13.<\/strong><\/span> Question 14.<\/strong><\/span> Question 15.<\/strong><\/span> Question 16.<\/strong><\/span> (b)<\/strong> The nucleus is a centrally located positively charged mass. Question 17.<\/strong><\/span> Question 18.<\/strong><\/span> Selina Concise Chemistry Class 8 ICSE Solutions – Atomic Structure ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 8 Chemistry Chapter 4 Atomic Structure. You can download the Selina Concise Chemistry ICSE Solutions for Class 8 with Free PDF download option. Selina Publishers Concise … Read more<\/a><\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"spay_email":""},"categories":[3034],"tags":[8434,8118,8117,8120,8122,8121,8119,7320,8116,8433,8124,8123,6283],"yoast_head":"\n
\n(b) An ion which has a positive charge is called a cation.<\/strong>
\n(c) The outermost shell of an atom is known as valence shell.<\/strong>
\n(d) The nucleus<\/strong> of an atom is very hard and dense.
\n(e) Neutrons are neutral<\/strong> particles having mass equal to that of protons.
\n(f) Isotopes are the atoms of an<\/strong> element having the same atomic number but a different mass number.<\/p>\n
\nfalse<\/strong>
\n(b) The maximum number of electrons in the first shell can be 8.
\nfalse<\/strong>
\n(c) The central pad of the atom is called nucleus.
\nTrue.<\/strong><\/p>\n
\n(b) Protons and neutrons present in the nucleus.
\n(c) The electrons present in the outermost shell.
\n(d) Arrangement of electrons in the shells of an atom.
\n(e) The number of protons present in the nucleus of an atom.
\n(f) The sum of the number of protons and neutrons of an atom.
\n(g) Atoms of same element with same atomic number but a different mass number.
\n(h) The smallest unit of an element which takes part in a chemical reaction.<\/p>\n
\n(b) Mass number
\n(c) Valency
\n(d) Orbits or Valence shells
\n(e) Atomic number
\n(f) Mass number
\n(g) Isotopes
\n(h) Atom<\/p>\n\n
\n
\n
\n
\n
\n
\nName three fundamental particles of the atom. Give the symbol with charge, on each particle.
\nAnswer:<\/strong><\/span>
\nThe fundamental particles of the atom are: electrons, protons and neutrons.<\/p>\n\n\n
\n Particle<\/strong><\/td>\n Symbol<\/strong><\/td>\n Charge<\/strong><\/td>\n<\/tr>\n \n electron<\/td>\n e–<\/sup><\/td>\n -1 or 1.602 x 10-19 <\/sup>C. Where -1 represent its one unit negative electrical charge<\/td>\n<\/tr>\n \n proton<\/td>\n p+<\/sup><\/td>\n + 1 or 1.602 x 10-19<\/sup> C. Where +1 represents one unit +ve electrical charge.<\/td>\n<\/tr>\n \n neutron<\/td>\n no<\/sup><\/td>\n 0<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\nDefine the following terms:
\n(a) Atomic number
\n(b) Mass number
\n(c) Nucleons
\n(d) Valence shell
\nAnswer:<\/strong><\/span>
\n(a) Atomic number:<\/strong> Atomic number refers to the number of protons present in an atom. It is denoted by Z. Example: An atom of oxygen contains 8 proton Therefore its atomic number is 8.
\n(b) Mass number:<\/strong> Mass number refers to the sum of the number of protons and neutrons present in the nucleus of an atom and denoted by A Mass number = Number of protons + Number of neutrons.
\n(c) Nucleons:<\/strong> The protons and neutrons collectively are known as nucleons.
\n(d) Valence Shell:<\/strong> The outermost shell of an atom is known as its valence shell.<\/p>\n
\nMention briefly the salient features of Dalton\u2019s atomic theory (five points).
\nAnswer:<\/strong><\/span>
\nSalient features of Dalton’s atomic theory:<\/strong><\/p>\n\n
\n(a) What are the two main features of Rutherford\u2019s atomic model?
\n(b) State its one drawback.
\nAnswer:<\/strong><\/span>
\n(a)<\/strong> According to Rutherford’s model an atom consists of:<\/p>\n\n
\nWhat are the observations of the experiment done by Rutherford in order to determine the structure of an atom?
\nAnswer:<\/strong><\/span>
\nFollowing were the observations made by Rutherford:<\/p>\n\n
\nState the mass number, the atomic number, number of neutrons and electronic configuration of the following atoms.
\n
\nAlso, draw atomic diagrams for them.
\nAnswer:
\n
\n
\n<\/strong><\/span><\/p>\n
\nWhat is variable valency? Name two elements having variable valency and state their valencies.
\nAnswer:<\/strong><\/span>
\nVariable valency: Some elements exhibit more than one valency. They are said to have variable valency, e.g. Iron, copper, tin, lead.
\nIron\u00a0 \u00a0 \u00a0 \u00a0 \u00a0Fe\u00a0 \u00a0 \u00a0 \u00a0Fe2+<\/span><\/sup><\/span> or Fe3+<\/span><\/sup><\/span>
\nCopper\u00a0 \u00a0cu\u00a0 \u00a0 \u00a0 \u00a0 cu+<\/span><\/sup><\/span> or cu2+<\/span><\/sup><\/span><\/p>\n
\nThe atomic number and the mass number of sodium are 11 and 23 respectively. What information is conveyed by this statement.
\nAnswer:<\/strong><\/span>
\nAtomic number = 11; No of protons = 11
\nMass number = 23 = Number of protons + Number of neutrons.
\nNo of neutrons = 23-11 = 12.<\/p>\n
\nDraw the diagrams representing the atomic structures of the following:
\n(a) Nitrogen (b) Neon
\nAnswer:
\n
\n<\/strong><\/span><\/p>\n
\nExplain the rule with example according to which electrons are filled in various energy levels,
\nAnswer:<\/strong><\/span>
\nThe maximum number of electrons that can be present in any shell or orbit of an atom is given by the formula 2n2<\/span><\/sup><\/span>, where n is the serial number of the shell.
\nTherefore:
\nK shell, n = 1, no. of electrons = 2 x 12<\/span><\/sup><\/span> = 2
\nL shell, n = 2, no. of electrons = 2 x 22<\/span><\/sup><\/span> = 8
\nM shell, n = 3, no. of electrons = 2 x 32<\/span><\/sup><\/span> = 18
\nN shell, n = 4, no. of electrons = 2 x 42<\/span><\/sup><\/span>= 32
\nElectrons are not accommodated in a given shell, unless the inner shells are filled.
\nThat is, the shells are filled in a stepwise manner.
\nExample:
\n
\n<\/strong><\/p>\n
\nThe atom of an element is made up of 4 protons, 5 neutrons and 4 electrons. What is its atomic number and mass number?
\nAnswer:<\/strong><\/span>
\nProtons = 4, neutrons = 5, electrons = 4
\nAtomic number = 4,
\nMass number = 4 + 5 = 9<\/p>\n
\n(a) What are the two main parts of which an atom is made of?
\n(b) Where is the nucleus of an atom situated ?
\n(c) What are orbits or shells of an atom ?
\nAnswer:<\/strong><\/span>
\n(a)<\/strong><\/p>\n\n
\n(c)<\/strong> The circular orbits (shell present) in the space available around the nucleus on which electrons revolve are called orbits or shells of an atom.<\/p>\n
\nWhat are isotopes? How does the existence of isotopes contradict Dalton\u2019s atomic theory?
\nAnswer:<\/strong><\/span>
\nAtoms of an element must have the same atomic number, but their mass number can be different due to the presence of different number of neutrons. These atoms of an element having different number of neutrons are called groups.
\nAccording to Dalton’s theory, all atoms of an element are similar to all respects, for example, they have the same shape, size etc. and have similar physical and chemical properties like mass, density and reactivity. Whereas isotopes of an element have atoms that are similar as they have same number of protons and electrons but differ in the number of neutrons. So, the isotopes have atoms that are not similar in all aspects.<\/p>\n
\nComplete the table below by identifying A, B, C, D, E andF.
\nAnswer:
\n<\/strong><\/span><\/p>\n","protected":false},"excerpt":{"rendered":"