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Working on NCERT Solutions for class 10 science chapter 5 notes will help candidates to build a strong foundation over the subject Science. Going through this periodic classification of elements class 10 NCERT activity solutions will help candidates to understand the theory behind every concept which in turn helps candidates to solve the questions at the end of every topics and subtopic.
Read on to find everything about the periodic classification of elements class 10 question and answers. Compare and find out. For example, Li, Na, K. If we consider lithium Li as the first element, then sodium Na is eighth element.
If we consider sodium as the first element, then potassium is the eighth element. Answer: It failed to arrange all the then known elements in the form of triads of elements having similar chemical properties. Dobereiner could identify only three triads from the elements known that time. Answer: i Newlands law of octaves was applicable to the classification of elements upto calcium only.
After calcium every eighth element did not possess the properties similar to that of the first element. For example, the two elements cobalt Co and nickel Ni were put together in just one slot and that too in the column of elements like fluorine, chlorine and bromine which have very different properties from these elements.
Question 2 Besides gallium, which other elements have since been discovered that were left by Mendeleev in his periodic table? Question 3 What were the criteria used by Mendeleev in creating his Periodic Table? Answer: Mendeleev used the relationship between the atomic masses of the elements and their physical and chemical properties.
He used similarity in physical properties, similarity in the formation of hydrides and oxides of element. Question 4 Why do you think the noble gases are placed in a separate group?
Answer: Noble gases are chemically inert and are present in atmosphere in extremely low concentrations. Therefore, owing to their similar inert behaviour and similar electronic configuration, they are justified to be placed in a separate group.
So they are alloted the same position in modern periodic table. Question 2 Name two elements you would expect to show chemical reactions similar to magnesium. What is the basis for your choice? Answer: Beryllium Be and Calcium Ca. Both Be atomic number 4 and Ca atomic number 20 have similar electronic configuration, i. Question 3 Name : a three elements that have a single electron in their outermost shells.
Answer: a Lithium : Atomic number � 3 2, 1 ; Sodium : Atomic number � 11 2, 8, 1 ; Potassium : Atomic number � 19 2, 8, 8, 1. Question 4 a Lithium, sodium, potassium are all metals that react with water to liberate hydrogen gas. Is there any similarity in the atoms of these elements? What, if anything, do their atoms have in common? Answer: a Lithium, sodium and potassium all belong to the same group. The atoms of lithium, sodium and potassium all have only one electron in their outermost shells and all of these are metals.
All of these react with water to form alkalies. Helium has its first shell completely filled, while neon has its first and second shells K and L completely filled. Question 5 In the modern periodic table, which are the metals among the first ten elements? Answer: The first ten elements in modern periodic table are hydrogen, helium, lithium, beryllium, boron, carbon, nitrogen, oxygen, fluorine and neon.
Out of these, lithium, beryllium and boron are metals, because they have 1, 2 and 3 electrons respectively in their outermost shells. Question 6 By considering their position in the Periodic Table, which one of the following elements would you expect to have maximum metallic characteristics? In the periodic table, the elements placed on the left show maximum metallic characteristics. Since beryllium occupies the most left position in comparison to other elements, hence it shows maximum metallic characteristics.
Question 1 Which of the following statements is not a correct statement about the trends wlien going from left to right across the periods of Periodic Table. Answer: c The atoms lose their. Question 2 Element X forms a chloride with the formula XCl 2 , which is solid with a high melting point. Question 3 Which element has a two shells, both of which are completely filled with electrons? Question 4 a What property do all elements in the same column of the Periodic Table as boron have in common?
Answer: a Elements in the same column or group as boron have valency of three and have three valence electrons. Question 5 An atom has electronic configuration 2, 8, 7. Atomic numbers are given in parentheses. Question 6 The positions of three elements A, B and C in the periodic table are shown below : a State whether A is a metal or non-metal.
Answer: a Since the valency of group 17 elements is 1 and all these elements accept electrons, thus A is a non-metal. Question 7 Nitrogen atomic number 7 and phosphorus atomic number 15 belong to group 15 of the periodic table.
Write the electronic configuration of these two elements. Which of these will be more electronegative? In a group of the periodic table, electron attracting tendency decreases as we move from top to bottom. Question 8 How does the electronic configuration of an atom relate to its position in the Modern Periodic Table? Answer: Modern periodic table is based on the atomic number and atomic number is directly related to the electronic configuration.
One can find the group number and period number of an element on the basis of electronic configuration. For example, if an element has 1 or 2 electrons in its outermost shell, then it would belong to group 1 or group 2. And if it has 3 or more electrons in its outermost shell, then it would belong to group 10 4- the number of electrons in the outermost shell. All the alkali metals have one electron in their outermost shell, so they are placed in group 1. Thus, all the group 2 elements have 2 electrons in their outermost shell.
In group 15 elements, there are 5 electrons in their outermost shell. Similarly, the number of shells in an element indicates its period number. For example, the atomic number of magnesium is 12 and its electronic configuration is 2, 8, 2. Thus it is an element of 3rd period. Question 9 In the Modern Periodic Table, calcium atomic number 20 is surrounded by elements with atomic number 12, 19, 21 and Which of these have physical and chemical properties resembling calcium?
Periodic classification of elements: Needs for classification, Modern Periodic table, gradation in properties, valency, atomic number, metallic and non-metallic properties. Formulae Handbook for Class 10 Maths and Science. Solution: All the known elements could not be arranged in the form of triads. Take the example of F, Cl and Br. Atomic mass of Cl is not an arithmetic mean of atomic masses of F and Br. Solution: It was not valid for elements that had atomic masses higher than Ca.
When more elements were discovered, such as elements from the noble gases such as He, Ne, Ar, they could not be accommodated in his table. Question 5 Besides gallium, which other elements have been left by Mendeleev in his periodic table, since the time they were discovered? Any two Solution: Scandium and Germanium. Question 6 What were the criteria used by Mendeleev in creating his periodic table?
Solution: He observed the relationship between the atomic masses of the elements and their physical properties. Among chemical properties, he concentrated on the compounds formed by elements with oxygen and hydrogen. Question 7 Why do you think, the noble gases are placed in a separate group? Solution: Due to its inert and low concentration in our atmosphere, they could be placed in a new group without disturbing the existing order.
For example, Position of isotopes: All the isotopes of an element have the same number of protons, so their atomic number is also the same. Since all the isotopes of an element have the same atomic number, they can be put at one place in the same group of the periodic table. Question 9 Name two elements, which you would expect to show chemical reactions similar to magnesium. Solution: Calcium and Beryllium are the elements that will show chemical reactions similar to magnesium.
This is because beryllium and calcium belong to the same group of periodic table as magnesium. All of them have similar electronic configurations with 2 valence electrons each. Question 10 Name: a. Three elements that have a single electron in their outermost shell. Two elements that have two electrons in their outermost shell.
Three elements with filled outermost shell. Solution: a. Three elements that have a single electron in their outermost shell are: 1. Lithium 2. Sodium 3. Potassium b. Two elements that have two electrons in their outermost shell are: 1. Magnesium 2. Calcium c. Three elements with filled outermost shell are: 1.
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