(e) Is ‘M’ a metal or a non-metal? (2011 D) Answer: (i) The ‘period number’ of an element is equal to the number of electron shells in its atom. Electronic configuration: (i) E This is due to an increase in nuclear charge which tends to pull the electrons closer to the nucleus and reduces the size of the atom. In the table you can see rows and columns, which represent the periods and groups or families. O3 → Ozone. (iii) Which of these elements will form the most basic oxide? (iii) X is more metallic than Y because metallic character decreases on moving from left to right in a period.
(iii) 19K and 20Ca belong to the same period as both have same number of energy shells (K, L, M, N). Content Guidelines 2.
Following data has been extracted from the records of a manufacturing company whose operations are varying from month to month. (iii) B Answer: No ambiguity should be there as the schedule or manual for which suitable remarks against the standing order numbers to assist in properly classifying each item of expenses is necessary. Thus, Newland’s classification was not accepted. Element ‘X’ that has atomic number = 13 (2015 OD) (2012 D, 2013 OD) Answer: So, element P belongs to 4th period and group 2, as it has four shells and 2 valence electrons. (2016 OD), (i) Write the electronic configuration of Ca. (a) Write its electron configuration. (a) Electronic configuration = Sometimes, they are also termed as shutdown or stand-by costs. Electronic configuration = 2, 8, 7 Based on the group valency of elements state the formula for the following giving justification for each: 4. (iii) The expenses per unit of production are more at lower ranges of output but gradually decrease with the increase in production. Electronic configuration = 2, 7 Moseley proposed this modern periodic table and according to which “the physical and chemical properties of elements are periodic function of their atomic number and not the horizontal rows called “periods”. (d) Noble gases like helium, neon, argon etc. of valence shells. non-metallic character) increases on moving than left to right in a period. Be < Mg < Ca < Rb, Question 42.
By solving the equation, the values of m and c are obtained which help in determining the relationship between fixed and variable costs. How do the valency and metallic character of elements vary on moving from left to right in a period? (a) Determine the valence electrons and the valency of ‘X’. Electronic configuration of X (2, 8, 7) (b) (i) Most metallic element is Na. atomic number = 12 (electronic configuration = 2, 8, 2) (b) E belongs to 3rd period as it has 3 energy shells. (a) Write its electron configuration. Explain the variation of the following properties of the element in the periodic table. Elements in the same row as one other are known as periods and they share the same highest unexcited electron energy level. (2015 D) (v) Noble gases. 20Ca, 3Li, 11Na, 10Ne These costs are partly fixed and partly variable. Similarity between Na and K: Both have one electron in their outermost shell. Because all have same number of energy shells (two). Answer: (a) D has 1 electron in the outermost shell. On the other hand, due to increased nuclear charge, it becomes easier for the atoms to gain electrons. Question 3. (i) How do you calculate the possible valency of an element from the electronic configuration of its atoms? (2016 D) Plagiarism Prevention 4. Answer: Let us make in-depth study of the definition, importance and classification of overheads. Because both have same valance electrons (4). Electronic configuration: 2, 8, 8, 2, (ii) Li(3) Newlands called it the Law of Octaves. (2012 D) (2011 OD) Question 7. The electronic configuration (2, 8, 2) of the element ‘M’ suggests that it belongs to group 2 and period 3 of the Modern Periodic Table and its valency is 2. All the elements in a group have same valency because the number of valence electrons in a group is same. Answer: (c) Mendeleev left some gaps in his Periodic Table as he predicted the existence of some elements that had not been discovered at that time. Period number = 3rd (d) Which has higher atomic mass, A1 or Cl? (ii) D (c) Semi-variable Cost (also called mixed cost or semi fixed cost) is a cost, containing both fixed and variable elements and which is thus partly affected by fluctuation in the level of activity. Atomic number of the element = 16 Li has 1+ valency, then Be2+, Be3+, C4+ covalency, N3- valency, then O2- and F(–) valency. Valency: 1, Element D: Question 6. Answer: Question 31. There are six periods in the periodic table. Atomic no. Taking the example of an element of atomic number 16, explain how the electronic configuration of the atom of an element relates to its position in the modern periodic table and how valency of an element is calculated on the basis of its atomic number. (ii) 4Be and 20Ca belong to the same group as both have same number of valence electrons (2). This is a statistical method and is based on finding out a line of best fit for a number of observations. Fixed expenses are incurred by management decisions and as such can be controlled by the top management while the variable expenses can be controlled by the lower levels of management. The atomic numbers of three elements A, B and C are 11,17 and 19 respectively. Compare them with respect to: (2011 D) Electronic configuration: Thus variable costs fluctuate in total amount in direct proportion to the volume of output but tend to remain constant per unit as production activity changes.
Answer: Semi-variable overheads are of two types: (a) The first type shows semi-variable costs where variable element operates at all the levels as shown in the graphs given below: Variable element operates at all the levels.
(b) Write the formula of the compound formed. (a) Which atom is bigger, Na or Mg?
State modem periodic law of classification of elements.
(i) Write the group to which these elements belong. For all production the variable expenditure per unit of production is constant. (iii) Valency in a group. (ii) Valency = 2 (ii) On moving from left to right in a period, the metallic character of elements decreases and non- metallic character increases. Following figures have been extracted from the books of a manufacturing company: Plot the above information on the graph to enable you to ascertain the fixed overhead of the company assuming that the cost-volume-profit relationship has been maintained throughout these months. How do the following change on moving from top to bottom in a group? An element P (atomic number 20) reacts with an element Q (atomic number 17) to form a compound. State, giving reason, which two elements will show similar properties.
In a group all the elements contain the same number of valence electrons. Fixed overhead expenses are thus period costs representing a constant amount of expenditure during a particular period. Question 25. (2013 OD) The atomic numbers of three elements, X, Y and Z are 9,11 and 17 respectively. 4Be, 9Fe, 44Si, 19K, 20Ga (vi) Let this element be represented by the symbol ‘X’. an expenditure which varies directly with variation in the volume of output. Answer: ADVERTISEMENTS: Let us make an in-depth study of Human Wants:- 1. (b) Which one of them is least reactive? It is a cost which tends to follow (in the short-term) the level of activity. Variable overheads by xy/x2 and thus fixed overhead will be calculated. Question 23. Question 14. The classification of elements into triads was very successful in predicting the atomic mass and properties of the middle element. (ii) Name the element which is a metal with valency three.
Atomic number = 20 Answer: How many groups and periods are there in the modern periodic table? The 5 main reasons for the importance of the periodic table 1- Order . (a) As different elements were being discovered, scientists gathered more information about the properties of these elements. Given: Element ‘M’, atomic number = 12 Answer: Two elements of group 1 If we take the highest and lowest points from the data, the variable and fixed cost can be calculated. Answer: (i) All these elements belong to the 2nd group as all have two electrons in their outermost shell. (v) Oxide of X = X2O, Oxide of Y = YO Answer: For example, if out of a semi-variable expense of Rs 6,000, 60% is variable then Rs 3,600 will be variable and rest Rs 2,400 will be fixed. Question 44. It also assists as a way of remembering and differentiating the types of organisms, making predictions about organisms of the same type, classifying the relationship between different organisms, and providing precise names for organisms. The number of valence electrons increases from 1 to 8 on going from left to right in a period. Periodic Classification of Elements Chapter Wise Important Questions Class 10 Science. Therefore the tendency of atoms to gain electrons decreases, due to which their reactivity decreases. (ii) its valencies; 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. Periodic Classification of Elements Important Questions “Atomic number of an element is considered to be a more appropriate parameter than its atomic mass for a chemist.” Take the example of element X (atomic number 13) to justify this statement. (d) Write the formula of its bromide.
This is an easy method though it creates a problem to estimate the extent of variability of an expense. (iii) Compounds formed when an element of group 2 combines with an element of group 16. Question 8. Under this method, the output at two different levels i.e. (2014 OD) Alexander Newlands arranged the elements in the increasing order of their atomic masses. Write the formula of and mention the nature of the compound formed by the union of 19K and element X (2, 8, 7).
(ii) Sodium is very reactive, Mg is less reactive whereas Al is still less reactive because on moving from left to right in a period, the chemical reactivity of metals decreases. Question 10. The electronic configuration of an element ‘X’ is 2, 8, 8, 2. (iv) D is bigger in size because as we move from left to right in a period, the size of the atom decreases as positive charge increases but the number of shells remains the same. Cost pertaining to a cost centre or cost unit may be divided into two portions direct and indirect. (vi) the formulae of their chlorides. (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. Grouping together of elements having similar properties, of making oxides and hydrides. The horizontal rows are called periods. As we move from left to right in a period, the atomic number of elements increases and the extra electrons are added to the same shell. Atomic size decreases along a period due to increase in the nuclear charge which tends to pull the electrons closer to the nucleus and reduces the size of the atom. K = 2,8,8,1 (a) Mendeleev was guided by two factors: (b) (i) Cl is the most reactive non-metal. (ii) Will its atomic radius be larger or smaller than that of potassium with atomic number 19? State its valency. These days we find that overhead expenses are increasing in every organisation. Rather than memorizing facts and figures for each element, students and scientists need only glance at the table to learn much about the reactivity of an element, whether it is likely to conduct electricity, whether it is hard or soft, and many other characteristics.
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