importance of classification of elements

The result is that a large number of establishments have grown up both in the public and private sectors for mass production for which use of improved and costlier and special type of machines has become absolutely necessary. Element ‘X’ has seven electrons in its outermost shell therefore it belongs to 17, Element ‘X’ has 3 shells (energy) thus it belongs to 3, Element ‘Y’ has 2 electrons in its outermost shell therefore it belongs to 2, Element ‘Y’ has 4 energy shells thus it belongs to 4.

He proposed a law known as Dobereiner’s law of triads. These days we find that overhead expenses are increasing in every organisation.

Answer: the tendaency of an atom to lose electrons on moving down in a group increases as valance electrons move more and more away from the nucleus and neuclear charge on electrons decreases. A concern may adopt one or more of the above classifications. (iv) On going down in a group, the size of the atoms increases as a new shell of electrons is added to the atoms at every step. The eight element starting from sodium is potassium. (a) Which two criteria did Mendeleev use to classify the elements in his periodic table? Metallic and non-metallic properties: In a period from left to right metallic nature decreases while non-metallic character increases. Explain the trends in the Modern Periodic Table of various properties like valency, atomic size, metallic and non-metallic properties of the atoms of elements. ‘X’ has 7 valence electrons since the group number of an element having more than 2 valence electrons is equal to the valence electrons plus 10. Electronic configuration of X = Ionic bond is formed between B and A. All the elements present in a particular group are chemically similar in nature. Fixed overhead cost (also called period cost and policy cost) is the cost which accrues in relation to the passage of time and which, within certain limits tends to be unaffected by fluctuations in the level of activity. Element ‘M’, atomic number = 11 (a) They all belong to 2nd group of the periodic table as all the elements have two valance electrons in their valance shell. (ii) Classify these elements as metals and non-metals. Question 2. All the elements of a period of the periodic table have same number of shells. Explain with one example. What similarity do you observe in their electronic configurations? The behaviour of the cost will also be forcefully brought out. This method is very simple but sometimes, it does not give accurate results. Following data has been extracted from the records of a manufacturing company whose operations are varying from month to month. (b) Atom of element C has a larger size than atom of element A. (iv) Atomic size down a group.

There fore, Lavoisier’s classification was found to be inadequate. This table was created with the purpose of organizing in a more structured and coherent way the existing elements, according to the chemical properties they possess. (2013 D, 2014 D) Atomic number of given element = 17 Similar results can be obtained if we arrange the data in the ascending and descending order and any set of two consecutive figures are compared. There are 18 vertical columns in the modern periodic table and they are called groups. As properties of an element depend on its valence electrons. The elements with valence electrons 5 to 8: Their valencies correspond to (8 – V.E.). (2014 OD) Question 8. Write the number of periods the modem periodic table has. Question 13. Examples of fixed expenses are rent of building, storage space etc., depreciation of plant and machinery, depreciation of buildings, pay and allowances of space etc., depreciation of plant and machinery, depreciation of buildings, pay and allowances of directors, managers, secretaries, accountants etc., office expenses, like stationery and postage etc., bank charges, legal expenses, salaries of the works manager, interest on capital, if included in costs. Fixed overhead cost per unit decreases as production increases and increases as production declines.

non-metallic character) increases on moving than left to right in a period. (it) On moving down in a group the number of occupied (filled) shells increases gradually. (c) This element is the 2nd member of this group. Element: ‘X’,

(b) It belongs to 2nd group because it has 2 valence electrons and the group number of an element having upto two valence electrons is equal to the number of valence electrons. The atomic numbers of three elements A, B and C are 11,17 and 19 respectively. (2011 OD) Variable cost at any level may be obtained by measuring the difference between fixed cost line and total Cost line. Write the name and formula of a molecule made up of three atoms of oxygen. (f) The formula of their chlorides   (2015 OD) The table can be used to predict the properties of elements, even those that have not yet been discovered. Na = 2,8,1 Electronic configuration = 2, 8, 8, 1 Write atomic number and electronic configuration of ‘XAlso write group number, period number and valency of ‘X’. (∵ Group no. High overhead costs do not indicate inefficiency if it is accompanied by: (i) Large scale production or mass production; (ii) Increase in efficiency and productivity of labour; (iii) Less human efforts will be required because of automatic machines but more machine expenses will have to be incurred; (iv) More depreciation, maintenance expenditure and similar other items because of more use of machinery; (v) Improved methods of managerial control like work study, production control, cost and management accountancy techniques may reduce the direct cost but will increase the overhead costs. In all the above methods discussed it is assumed that prices are at a constant level and movements in costs have been caused by changes in volume only. Classify the following items of expenses by functions and variability: (h) Commission on sales paid to salesmen; (I) Experimental expenses to develop a product; (m) Compensation (fixed salary plus commission on sales). As you move from top to bottom down a column of elements, the atomic radius increases, ionization energy decreases, electron affinity usually decreases, and electronegativity decreases. (b) All the members of the same period have different properties because the elements of a period have different valence electrons. Answer: Elements A and C will show similar properties as both have same number of valence electrons. The atomic size of an atom is the distance between the centre of the nucleus and outermost electron shell of an isolated atom. It was observed that it was difficult to organise all the information or properties of these elements. Because all have same number of energy shells (two). (iii) S forms -2 charged ion. Answer:

(a) Why do we classify elements?

Why? Based on this behaviour, the expenses may be classified into: (c) Semi-variable or Semi­-fixed overhead. depreciation, salary, repairs and maintenance etc. The definition that fixed overheads remain constant in spite of increase or decrease in the level of activity will hold true only in short period during which no appreciable change in capacity occurs.

So as the number of shells increases so does the size of the atom. The cost accountant is required to pay so much attention to the accounting of overhead cost as prudence choice of various bases used for apportionment and absorbing the overheads in the cost of products has to be made by him. However, it is desirable to have most effective utilisation of plant capacity in order to reduce the fixed cost per unit to the minimum. Question 3. (a) Write its electronic configuration. The position of three elements A, B and C in the Periodic Table are shown below: Giving reasons, explain the following: How many horizontal rows are there in the modern periodic table and what are they called? Answer: (a) As different elements were being discovered, scientists gathered more information about the properties of these elements. (d) Noble gases like helium, neon, argon etc. (iv) Metallic character of elements

(b) X is a metal as it loses electrons to acquire inert gas configuration and an element which loses (b) The second type shows semi-variable costs where variable element comes into operation after a certain level of activity level as shown in the graph given above: Variable element comes into operation after a certain range. (i) Elements that should be in the same period. Answer: The properties of lithium, sodium and potassium are similar. (i) Valency (iii) Draw the electron dot structure of the compound and state the nature of the bond formed between the two elements. Fixed overhead falls under the category of non-controllable cost from the management control point of view as there is practically no scope of reduction of the amount of expenditure by the action of any executive once certain facilities are installed. (e) The two isotopes of chlorine Cl-35 and Cl-37 would be placed in different slots of Mendeleev’s Periodic Table as both have different atomic masses. Its size is greater than the 1st member (2, 7) and smaller than the rest of the other members of that group because size of the atom increases on going down in a group as one energy shell is added at every step.

(iv) forms ion with +2 charge? Examples are canteen staff wages, supervisor’s salary etc.

The number of compounds discovering by Scientist was enormous. Modem periodic law states “that the properties of elements are a periodic function of their atomic numbers”. The fixed overhead rate serves as a measure of utilisation of the facilities while the extent of idle capacity is indicated by under absorption. (iii) Compounds formed when an element of group 2 combines with an element of group 16. (e) Would you place the two isotopes of Chlorine, Cl-35 and Cl-37 in different slots because of their different atomic masses or in the same slot because their chemical properties are the same? (b) The sizes of their atoms Chhand in Hindi (छन्द) | छंद की परिभाषा, प्रकार, भेद और उदाहरण – हिन्दी व्याकरण, Average of the atomic masses of calcium and barium, Average of the atomic masses of lithium and potassium, Average of the atomic masses of chlorine and iodine. (i) Elements of same period 6C, 8O, 10Ne (i.e.

Answer the following questions, giving justification in each case:

Question 10. Three elements ‘X’, ‘Y’ and ‘Z’ have atomic numbers 7, 8 and 9 respectively.

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