Title कक्षा -९, विज्ञान, तत्वहरूको वर्गीकरण, नेपाली+अङ्ग्रेजी माध्यम.pdf ✅

1 1. tŒjsf]pbfx/0f;lxt kl/efiff lbg'xf];\. Define element with examples. pQ/M To:tf] ;/n / z'4 kbfy{ h;nfO{ Tof] eGbf ;/n kbfy{df kl/jt{g ug{ ;lsb}+g, To;nfO{ tŒj elgG5 . h:t}M kmnfd, tfdf, ;'g, xfO8«f]hg, clS;hg, kf/f], cflb . Pure and the simplest substance which cannot be broken down into simpler substances than itself is called element. 2. of}lussf] pbfx/0f;lxt kl/efiff lbg'xf];\. Define compound with examples. pQ/M b'O{ jf ;f] eGbf al9 k|sf/sf tŒjx?lar /f;folgs k|ltlqmof eO{ ag]sf] z'4 kbfy{ h;nfO{ cem ;/n kbfy{df kl/jt{g ug{ ;lsG5, To;nfO{ of}lus elgG5 . h:t}M kfgL, g'g, t]n, sfa{g 8fOcS;fO8, cflb The pure substance formed by the chemical reaction between two or more elements which can be further broken down into simpler substances is called compound. gf]6M xfn;Dd 92 cf]6f k|fs[lts / 26 cf]6f s[lqd u/L hDdf 118 cf]6f tŒjx? kQf nflu;s]sf 5g\. Till now, 118 elements have been discovered as 92 natural and 26 artificial. 3. k/df0f'sf] kl/efiff lbg'xf];\. Define atom. pQ/M /f;folgs k|ltlqmofdf efu lng ;Sg] tŒjsf] ;a}eGbf ;fgf] s0fnfO{ k/df0f' elgG5 . The smallest particle of an element which takes part in chemical reaction is called atom. 4. c0f'sf] kl/efiff lbg'xf];\. Define molecule. pQ/M /f;folgs k|ltlqmofdf efu glng] tŒj jf of}lussf ;a} u'0fx? oyfjt\/x]sf] ;a}eGbf ;fgf] s0fnfO{ c0f' elgG5 . The smallest particle of an element or compound that keeps its property constant and cannot take part in chemical reaction is called molecule. gf]6 1M Pp6} tŒjsf k/df0f'x? ;dfg lsl;dsf x'G5g\eg] km/s km/s tTjsf k/df0f'x? km/s km/s x'G5g\ . h:t} xfO8«f]hg tŒjsf] k/df0f' lxlnodsf] eGbf km/s x'G5 . o;/L 118 cf]6f tŒjsf 118 k|sf/s} k/df0f' x'G5g\ . Atoms of same element are similar while atoms of different elements are different. So, 118 elements have 118 types of atmos. gf]6 2M tŒjsf c0f'x? ;dfg lsl;dsf k/df0f' ldn]/ ag]sf x'G5g\eg] of}lussf c0f'x? km/s–km/s k/df0f' ldn]/ ag]sf x'G5g\. Molecule of element is made up of similar types of atoms whereas molecule of compound is made up of different types of atoms. h:t}(For example): xfO8f«]hgsf] c0f'sf] (Molecule of hydrogen) Ö H2 -b'O cf]6f xfO8«f]hgsf] k/df0f'x? ldn]/ ag]sf]÷made up of two hydrogen atoms_ kfgLsf] c0f' Ö H2O -b'O cf]6f xfO8«f]hgsf] k/df0f' / Pp6f clS;hgsf] k/df0f' ldn]/ ag]sf]÷made up of two hydrogen atoms and one oxygen atom_ 5. k/df0f'sf] ;+/rgf ;lrq j0f{g ug'{xf];\. Describe structure of atom with diagram. pQ/M k/df0f' cToGt ;fgf] x'G5 . o;nfO{ gfa\uf] cfFvfn] b]Vg ;lsb}+g . k/df0f' c? ;–;fgf tLg cf]6f s0fx? ldnL ag]sf] x'G5 h;nfO{ pkkf/df0fljs s0f elgG5 . ltgLx? k|f]6f]g, Go'6«f]g / On]S6«f]g x'g\. k|f]6f]g / Go'6«f]g k/df0f'sf] s]Gb|df vfFlbP/ /x]sf x'G5g\h;nfO{ Go'lSno; elgG5 . On]S6f«]gx? Go'lSno;sf] j/Lk/L lglZrt af6fdf 3'ld/x]sf x'G5g\. On]S6«f]g 3'Dg] af6fnfO{ sIf jf cla{6 jf ;]n jf OghL{ n]en elgG5 . ljleGg cfsf/sf ;a;]nx? ldn]/ ;]n ag]sf] x'G5 . To:tf ;a;]n s'g} uf]nfsf/ / s'g} 8d? cfsf/sf x'G5g\. Atom is extremely small which can not be seen through naked eyes. It is further made up three smaller particles called sub-atomic particles. They are proton, neutron and electron. Proton and neutron lie together at the centre of atom called nucleus. Electrons revolve round the
2 nucleus in a fixed path called orbit/ shell/ energy level. Sub shells of different shapes combine together to form a shell. Some of that sub shells are spherical and some are dumb bell shaped. 6. k/df0f'sf ;]ndf x'g] ;a;]nx? / ltgdf c6\g ;Sg] clwstd On]S6«f]gx?sf] ;a\VofM The sub shells present in the shell of atom and the maximum number of electrons that can fit in them: 7. On]S6«f]lgs ljGof;sf] kl/efiff lbg'xf];\. On]S6«f]lgs ljGof; slt t/Lsfn] ug{ ;lsG5 < Define electronic configuration. In how many ways, can electronic configuration be done ? pQ/M k/df0f'df ePsf On]S6«f]gx? Go'lSno;sf] jl/kl/ lglZrt lgodsf] cfwf/df ljleGg ;]n tyf ;a;]nx?df ldn]/ a:g] t/LsfnfO{ On]S6«f]lgs ljGof; elgG5 . The systematic distribution of electrons in an atom around the nucleus in various shells and sub shells according to certain rule is called electronic configuration. k/df0f'sf] On]S6«f]lgs ljGof; b'O{ t/Lsfaf6 ug{ ;lsG5M Electronic configuration of atom can be done by two ways: i) ;]nsf] cfwf/df (On the basis of shell): o;df 2n2 ;"q / af]/–a'/L lgodsf] cfwf/df ljGof; ul/G5 . t/ 2n2 lgod kf/df0fljs ;a\Vof 1 b]lv 18 ;Ddsf tŒjx?df dfq nfu" x'G5 lsgeg] af]/–a'/L lgod cg';f/ ;a}eGbf aflx/L sIfdf 8 cf]6f eGbf al9 On]S6«f]g /xg ;Sb}g ..In this method, 2n2 formula and Bohr-Burry rule is used for electronic configuration. But 2n2 rule is only applicable for the elements upto atomic number 18 because according to Bohr-Burry rule, the outermost shell (valence shell) must not contain more than 8 electrons. ii) ;a;]nsf] cfwf/df (On the basis of sub shell): o;df cˆaf]sf] l;¢fGt (Aufbau's principle) k|of]u u/L On]S6«f]lgs ljGof; ul/G5 . In this method, Aufbau's principle is used for electronic configuration. 8. 2n 2 n] s] hgfpF5 < pbfx/0f;lxt n]Vg'xf];\. What is 2n2 rule ? Write with examples. pQ/M 2n2 n] k/df0f'df s'g sIfdf slt cf]6f On]S6«f]g c6fpg ;S5g\eGg] hgfpF5 h;df n eg]sf] sIfsf] ;a\Vof xf] . The rule to find the number of electrons that each shell can hold is called 2n2 rule where n stands for no. of shell. h:t}(For example):
3 9. ;a;]nsf] cfwf/df On]S6«f]g ljGof; ubf{ k|To]s ;a ;]ndf clwstd ;a\Vofdf /xg] On]S6«f]gsf] ;a\Vof n]Vg'xf];\. Write the maximum number of electrons that a sub shell can hold during electronic configuration on the basis of sub shell. pQ/M ;a;]nsf] cfwf/df On]S6«f]g ljGof; ubf{ k|To]s ;a ;]ndf clwstd ;a\Vofdf /xg] On]S6«f]gsf] ;a\Vof o;k|sf/ 5g\M The maximum number of electrons that a sub shell can hold during electronic configuration on the basis of sub shell are: ;a;]n s p d f On]S6«f]gsf] ;a\Vof 2 6 10 14 10. ;a;]nsf] cfwf/df On]S6«f]g ljGof; ubf{ ;a;]ndf On]S6«f]g /fVg] qmd n]Vg'xf];\. Write the order of electrons in the sub shell during electronic configuration on the basis of sub shell. pQ/M ;a;]nsf] cfwf/df On]S6«f]g ljGof; ubf{ cˆaf]sf] l;¢fGt cg';f/ ;a;]ndf On]S6«f]g /fVg] qmd o;k|sf/ 5g\M The order of electrons in the sub shell during electronic configuration on the basis of sub shell are: 1s → 2s → 2p → 3s → 3p → 4s → 3d → 4p → 5s .................... 11. ;+o'Hotf ;"rs On]S6«f]g eg]sf] s] xf] < What is valence electron ? pQ/M k/df0f'sf] ;a}eGbf aflx/L ;]n jf sIfdf /x]sf On]S6«f]gx?nfO{ ;+o'Hotf ;"rs On]S6«f]g elgG5 . The electrons present in the outermost shell of an atom is called valence electron. 12. ;+o'Hotf ;"rs ;]n / sf]/ eGgfn] s] a'lemG5 < What is meant by valence shell and core ? pQ/M k/df0f'sf] ;a}eGbf aflx/L ;]nnfO{ ;+o'Hotf ;"rs ;]n elgG5 . To;}u/L k/df0f'sf] ;+o'Hotf ;"rs ;]n eGbf leqsf] c+znfO{ sf]/ elgG5 . The outermost shell of an atom is called valence shell. The inner part except the valence shell of an atom is called core.
4 13. ;+o'Hotf eg]sf] s] xf] < What is valency ? pQ/M s'g} tŒjsf] k/df0f'n] csf]{ tŒjsf] k/df0f';Fu /f;folgs k|ltlqmof u/L of}lus agfpFbf lng] jf lbg] jf ;fem]bf/L ug]{ On]S6«f]gsf] ;a\VofnfO{ g} ;+o'Hotf elgG5 . The number of electrons lost, gained or shared by an atom during chemical reaction with another atom to form compound is called valency. 14. km/s ;+o'Hotf eGgfn] s] a'lemG5 < What is variable valency ? pQ/M s'g} s'g} tŒjx?sf] ;+o'Hotf Ps eGbf al9 x'g'nfO{ km/s ;+o'Hotf elgG5 . The valency of some elements is more than one which is called variable valency. 15. s'g} s'g} tŒjsf] ;+o'Hotf Ps eGbf al9 x'g'sf] sf/0f s] xf] < Why do some elements have more than one valency ? pQ/M /f;folgs k|ltlqmofsf qmddf sltko tŒjsf k/df0f'x?df ;+o'Hotf ;"rs ;]nsf On]S6«f]gn] dfq geP/ Tof] eGbf leqsf] ;]ndf /x]sf On]S6«f]gn] ;d]t k|ltlqmofdf efu lng] ePsfn] Ps eGbf al9 ;+o'Hotf x'G5 . Not only the electrons of valence shell but electrons of penultimate shell also take part in chemical reaction in the atoms of some elements. That is why some elements possess variable valency. pbfx/0fsf] nflu, For example, tŒjsf] gfd (Name of element) tŒjsf] ;+s]t (Symbol of element) km/s ;+o'Hotf (Variable valency) kmnfd (Iron) Fe (Ferrum) 2,3 tfdf (Copper) Cu (Cuprum) 1,2 rfFbL (Silver) Ag (Argentum) 1,2 ;'g (Gold) Au (Aurum) 1,3 l;;f (Lead) Pb (Plumbum) 2,4 kf/f] (Mercury) Hg (Hydragyrum) 1,2 16. ;]n / ;a;]nsf] cfwf/df ul/Psf] s]xL tŒjx?sf On]S6«f]g ljGof; / ;+o'HotfM The electronic configuration and valency of some elements on the basis of shell and sub shell kf=;+= (A.N.) tŒj (Element) On]S6«f]g ljGof; (Electronic configuration) ;+o'Hotf ;]nsf] cfwf/df (Valency) (On the basis of shell) ;a;]nsf] cfwf/df (On the basis of sub shell) K L M N 1 Hydrogen 1 1s1 1 2 Helium 2 1s2 0 3 Lithium 2 1 1s2 , 2s1 1 4 Beryllium 2 2 1s2, 2s2 2 5 Boron 2 3 1s2 , 2s2 , 2p1 3 6 Carbon 2 4 1s2 , 2s2 , 2p2 4 7 Nitrogen 2 5 1s2 , 2s2 , 2p3 3 8 Oxygen 2 6 1s2 , 2s2 , 2p4 2 9 Fluorine 2 7 1s2 , 2s2 , 2p5 1 10 Neon 2 8 1s2 , 2s2 , 2p6 0 11 Sodium 2 8 1 1s2 , 2s2 , 2p6 , 3s1 1 12 Magnesium 2 8 2 1s2 , 2s2 , 2p6 , 3s2 2 13 Aluminium 2 8 3 1s2 , 2s2 , 2p6 , 3s2 , 3p1 3 14 Silicon 2 8 4 1s2 , 2s2 , 2p6 , 3s2 , 3p2 4 15 Phosphorous 2 8 5 1s2 , 2s2 , 2p6 , 3s2 , 3p3 3