Answer the following questions giving reasons: Answer: Period number = Number of shells The atom of the element has three shells. The combining capacity of an element is called its valency. (b) An element with variable (more than one) valency stored underwater. Atomic size and metallic character of elements decreases from left to right in a period. The chemical properties of an atom are largely determined by its valence electrons. A and B have 2 shells thus belong to 2nd period of the periodic table. So, it has 1 valence electrons and it forms unipositive ion by losing its valence electron. Question 10. (a) (i) F and Cl, (ii) Na and K, ∴ Valence electrons = 6 The modern periodic table has been evolved through the early attempts of Dobereiner, Newland and Mendeleev. Why does atomic radius decrease across a period? (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? So the removal of electrons from its valence shell will be difficult. Group I elements contain 1 electron in their outermost shells. (ii) C and Si should be in the same group as these elements have same number of valence electrons. Question 34. Question 48. (iii) 19K and 20Ca belong to the same period as both have same number of energy shells (K, L, M, N). For example, each element of group I has one electron in its outermost shell. (a) Element A is a non-metal. (i) C, O, Ne should be in the same period as these elements contain same number of shells. Write the formula of oxide of any of the aforesaid element. Answer: Because all have same number of energy shells (two). Question 3. As properties of an element depend on its valence electrons. (i) Atomic size and metallic character of the elements increases down a group. 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. (v) What would be the ratio of numbr of combining atoms in a compound formed by the combination of element A with carbon? Answer: Give reason to justify your answer in each case. Non-metallic character increases from left to right in a period due to increase in the electro-negativity and this character decreases from top to bottom in a group due to decrease in the electro-negativity of atoms while going down in a group. (b) Cl < Br < I < At as the atomic radii increases down a group. (a) Write its electronic configuration. (b) Identify the most (i) metallic and (ii) non-metallic element in Period 3. (a) Noble gas —G The position of three elements A, B and C in the Periodic Table is shown below: Answer: (c) Why did Mendeleev leave some gaps in his Periodic Table? The elements of the third period of the Periodic Table are given below: An element ‘M’ has atomic number 11:  (2012 D) (c). Answer: atomic number = 12  (electronic configuration = 2, 8, 2) Question 2. (b) How do the valency and the atomic size of the elements vary while going from left to right along a period in the modem periodic table? (a) E Name any two elements of group one and write their electronic configurations. The electronic configuration of an element ‘X’ is 2, 8, 8, 2. (b) Most active metal—B (∵ Group no. (ii) VII group and 2nd period. (a) ‘X’ belongs to 4th period because ‘X’ has four energy shells and energy shell number corresponds to the period number. How doesd the size of ayomic radius vary on moving left to right in a horizontal row? Answer: List any two properties of the elements belonging to the first group of the modern periodic table. Answer: Valency in a particular period from left to right first increases as positive valency and then decreases as negative valency. Question 8. Periodic Classification of Elements Class 10 Important Questions Long Answer Type. The atomic number of nitrogen, oxygen and fluorine are 7, 8 and 9 respectively. (c) Is ‘X’ a metal or a non-metal? (iii) Select two elements that belong to the same period. But valancy of oxygen is 2 Answer: (a) All these elements belong to 1st group because all elements have one electron in their respective outermost shell. (b) ‘X’ belongs to 2nd group because ‘X’ has 2 electrons in its outermost shell and valence electrons (1, 2) corresponds to the group number of the element. Thus the bond between Y and X is ionic and formula is given by. (iii) Atomic radius in moving from left to right along a period. (ii) D Write the name and formula of a molecule made up of three atoms of oxygen. MCQ Questions for Class 10 Science with Answers were prepared based on the latest exam pattern. The atomic number of an element ‘X’ is 19. 10 + V.E. (i) is the most reactive non-metal? This is because new sells are being added as we go down the group. (c) Ca has the largest atomic size as Ca has the maximum number of shells and atomic size increases down the group. Na = 2,8,1 Question 13. (b) Newland’s Law of Octaves. (b) ‘X’ belongs to 13th group. (ii) Li and Na belong to the same group as both have same number of valence electrons (1). Step by Step Solutions of Eercise-1 , Eercise-2 and Objective Type Questions .Solved Questions of Goyal Brothers Prakashan Chemistry Chapter-1 Periodic Table Properties for ICSE Class 10. Answer: Give reason in support of your answer in the above two cases. Answer: of valence electrons = 6 Mass number = 35 (ii) The elements of group I are called alkali metals because they react with water to liberate H, gas and form alkalis. (i) Valency This is because nuclear charge increases from the right in a period which tends to pull the electrons closer to the nucleus. As on moving from left to right in a period, the atomic number of the elements increases which means that the number of protons and electrons in the atoms increases (the extra electrons being added to the same shell). (b) State the group to which ‘X’ belongs? Answer: (b) The sizes of their atoms (i) Elements that should be in the same period. (i) To which group or period of the periodic table do the listed elements belong? Their electronic configurations : Na = 2, 8, 1; K = 2, 8, 8, 1 (a) Identify the element X. Electronic configuration : 2, 8, 8, 2 This is an important topic, and questions usually get repeated. Properties of the elements are given below. Who classified the elements on the basis of fundamental properties of elements like atomic mass. The formulae of the hydrides and oxides formed by an element were treated as one of the basic propeties of an element for its classification. (2013 D, 2015 D) (a), (b) Valency of element ‘X’ is 1 and it is a non-metal whereas the valency of element ‘Y’ is 2 and it is a metal. (c) 2, 8, 7 Atomic size increases down a group due to increase in the number of shells. Group number = 17th ∴ Chemical Formula: (iii) Compounds of element of group 2 combines with an element of group 16 (Y): List one advantage and one … Question 26. (b) Which one of them is least reactive? Question 1. (c) Their tendencies to lose electrons (2015 OD) What is meant by ‘group’ in the modem periodic table? (c) Which two elements amongst these belong to the same period? (ii) K(19) is placed before Ca(20) in the same period (fourth period). Feb 19, 2021 - Chemistry Test Paper - Periodic Tables, Class 10 (ICSE) Class 10 Notes | EduRev is made by best teachers of Class 10. Therefore the first element in every period has 1 valence electron and the last element in every period has 8 valence electrons (except in the first period where last element helium has only 2 valence electrons). (d) State the valency of the element E. (i) Atomic radius in a period. Answer: There are 18 vertical columns in the modern periodic table and they are called groups. Question 2. (iii) What is the number of shells in Sr? (i) What is the valency of Q? Electronic configuration = 2, 8, 8, 1 Non-metals are found on the right side of the Modern Periodic Table. In the modern periodic table, the element Calcium (atomic number = 20) is surrounded by elements with atomic numbers 12,19, 21 and 38. (d) Write the formula of its chloride (i) Arrange these elements in the increasing order of their atomic radii. This is known as periodicity. Question 21. The basic property of elements used in the Modern Periodic Table is the atomic number of the elements. Answer the following questions giving the reason. So the tendency to gain electrons (i.e. Answer: (a) In which group should they be? Question 17. State its valency. But becauseof their similar chemical properties which is a more reliable property as it is based on the number of valence electrons, they would be placed in the same slot. The oxides of metals are basic in nature. But, it was difficult to study all the information or properties of these elements. Question 6. (iii) metallic character; (b) On moving from left to right in a period the size of the atom decreases because number of energy shells remains same in a period but nuclear charge increases from left to right and thus the force of attraction between the nucleus and the electrons increases which reduces the size of the atoms on moving from left to right in a period. State the fundamental property on which the modern periodic table or long form of periodic table is based. (i) Element ‘A’: O3 → Ozone. Explain why sodium is more reactive than lithium. Valency down a group remains the same. If an element X is placed in group 14, what will be the formula and the nature of bonding of its chloride? Answer: Choose from the following: 6C, 8O, 10Ne, 11Na, 14Si. This resamblance is called diagonal relationship. Explain the diagonal relationship by taking exmaple of lithium (Li) and magnesium (Mg). Question 51. Justify your answer in each case. Na, Mg and Al are the elements of the same period of Modern Table having one, two and three valence electrons respectively. (ii) The atomic number of sulphur = 16. (2014 OD) Compare their following characteristics in tabular form: On going down in a group of the periodic table, the size of atoms increases because a new shell of electrons is added to the atoms at every step on moving down in a group. Answer: Question 10. ∴ Valancy = 8 – 7 = 1. (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. Valency of R : 8 – 5 = 3. (a) Since X belongs to 13th group, therefore its valence electrons = 3. (v) Noble gases. (ii), Question 29. The electronic configuration of an element M is 2, 8, 4. Answer: Answer: Question 36. (f) Write the formula of its oxide. (2012 OD) Answer: (i) Is calcium a metal or non-metal? Period number = 3rd (ii) Number of valence electrons of elements on moving from left to right in a period. Which one of the two has bigger atomic radius? State the period in which these elements can be placed in the modern periodic table. (c) Basic oxide (X2O) ∴ Compound formed is Aluminium chloride and molecular formula of compound is AlCl3. Electronic configuration = Answer: (b) X > Y > Z From the following elements: (2015 D) The oxide of D is almost neutral. (b) The three compounds are X (NO3)2, XSO4, and X3(PO4)2. Atomic number of the element is given in the parentheses: A(4), B(9), C(14), D(19), E(20) Answer: Atomic number = 17 Question 6. Formula is PQ2 because valency of P is 2 and that of Q is 1. (iv) whether it is a metal or a non-metal; Question 28. Given below are some elements of the Modern Periodic Table. Valence electrons = 7 Mendeleev’s periodic table is based on _____ (a) Atomic number (b) Atomic weight (c) Equivalent weight (d) None of these. (d) Which has higher atomic mass, A1 or Cl? Thus, the valency of sulphur = 2. (2015 OD) Answer: Question 14. (ii) Atomic size (ii), Example: If the electronic configuration of an element is 2, 8, 7 ∴ Chemical Formula: (ii) Halides of the elements of group 13 (Let it be M): Answer the following questions associted with these elements, giving reason in each case: Compare their following characteristics in tabular form: Write the electronic configuration of these two elements in terms of K, L, M, N shell Predict whether these are metallic or non-metallic. Give reason for your answer. Mendeleev’s Periodic Law states that, “The properties of the elements are periodic function their atomic masses.”, Question 3. Element ‘M’, atomic number = 11 Simultaneously, atomic mass increases. 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 number of given element = 17 (c) On going from left to right along a period (short period), the valency of elements increase from 1 to 4 and then decreases to 0 (zero). Hence, the electrons are pulled in closer to the nucleus which leads to contraction of the atom and thus atomic radius decreases. Electronic configuration = 2, 8, 7 Write electronic configuration of calcium. (d) Write a common name for the family of elements Cand E. (v) the nature of oxide formed by it; The atomic numbers of three elements, X, Y and Z are 9,11 and 17 respectively. Question 50. Justify your answer stating reason for each. 10th std Science Periodic Classification of elements Exercise Questions and answers class 10 Lesson2 10th std Science Periodic Classification of elements Exercise Questions and answers class 10 Lesson2 von Suhani S. Suryawanshi vor 6 Monaten 31 Minuten 55.911 Aufrufe SuhaniSuryawanshi Name the basic property of elements used in the development of Modern Periodic Table. The electronic configuration of calcium is- 2,8,8,2. (iii) Sr (38) belongs to 5th period. (vii) A 4Be; 9F ; 19K; 20Ca Two elements ‘P’ and ‘Q’ belong to the same period of the modem periodic table and are in Group-1 and Group-2 respectively. Atoms of seven elements A, B, C, D, E, F and G have a different number of electronic shells but have the same number of electrons in their outermost shells. Question 12. Valence electrons: 7 Would you place the two isotopes of chlorine, Cl-35 and Cl-37 in different slots because their different atomic masses or in the same because their chemical properties are the same? So, it shares its 4 electrons and forms covalent bond with 4 chlorine atoms. Answer: Calcium (Ca) There are 18 groups and 7 periods in the Modern Periodic Table. State giving reason which two elements will show similar chemical properties. Feb 17, 2021 - Practice Questions - Periodic Table, Class 10, Science Class 10 Notes | EduRev is made by best teachers of Class 10. (a) (i) Valency. atomic number = 38  (electronic configuration = 2, 8, 18, 8, 2). The electronic configuration of an element ‘X’ is 2, 8, 8, 2. Question 7. The atomic radius decreases in moving from left to right along a period. This is because ability to lose electrons increases on moving down the group due to increase in distance between the nucleus and the valence electrons. 20Ca, 3Li, 11Na, 10Ne ‘B’ belongs to 1st group as it has one electron in its outermost shell. Where would you locate the following elements of the Periodic Table? Li has 1+ valency, then Be2+, Be3+, C4+ covalency, N3- valency, then O2- and F(–) valency. An element ‘X’ belongs to 3rd period and group 16 of the Modern Periodic Table. Answer: (a) In which group of the periodic table should they be? (f) The formula of their chlorides Elements belonging to same group have same number of valence electrons and thus same valency. (iv) Atomic size down a group. 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.
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