Periodic classification of elements: Class 10 Chemistry Q&A · Page 2
96 free answers on Periodic classification of elements (Chemistry) for Class 10 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- ChemistryClass 10ICSE
What is a group in the periodic table? In which part of a group would you separately expect the elements to have (i) the greatest metallic character (ii) the largest atomic size ? (b) In what respects do the properties of group 1 elements differ from those of group 17 elements? Explain with examples by taking one element from each group. (c) From the standpoint of atomic structure, what determines which element will be the first and which the last in a period of the periodic table? (d) Explain why, the properties of elements are repeated after 2, 8, 18 and 32 elements in the periodic table. What are the advantages of the periodic table?
Sodium has smaller size than chlorine and chlorine have larger atomic size Sodium is a metal and chlorine is non-metal. Sodium is electropositive and chlorine is electronegative. The number of valence electrons in atom determines which element will be first and which is last in the periodic table. The electronic configuration are repeated because 2,8,18 and 32 are the maximum number of electrons than can be occupied by shells K, L, M and N. The properties are
- ChemistryClass 10ICSE
Explain why, the first period of the modern periodic table has only two elements whereas second period has eight elements (b) Why do elements in the same group show similar properties but the elements in different groups show different properties? (c) For each of the following triads, name the element with the characteristics specified below: Element Least atomic radius Chemically least reactive (i) F, Cl, Br (ii) Li, Na, K ……………………… ………………………. …………………………………. …………………………………. (d) State one reason for keeping fluorine and chlorine in the same group of the periodic table. What are the merits of the modern periodic table of elements?
The first period of the modern periodic table has only two elements whereas second period has eight elements because the first electron can take maximum of 2 electrons only and in 2nd period the maximum number of electron which can be put in the 2nd shell is 8. Elements in the same group show similar properties but the elements in different groups show different properties because of the difference in electronic configuration. (c)(c) (i)
- ChemistryClass 10ICSE
What are the periods and groups in a periodic table? Give two characteristics of each. (b) In terms of electronic configurations, explain the variation in the size of the atoms of the elements belonging to the same period and same group. (c) Given alongside is a part of the periodic table. As we move vertically downward from Li to Fr: Li Be Na K Rb Cs Fr Ra (i) What happens to the size of atoms? (ii) What happens to their metallic character? (d) Name two properties of elements whose magnitudes change when going from top to bottom in a group of the periodic table. In what manner do they change? (e) Rewrite the following statement after correction, if necessary: Groups have elements with consecutive atomic numbers.
The horizontal rows of elements in a periodic table are called Characteristics: The elements in a period have consecutive atomic The of elements in period is fixed by the maximum no. of electrons which can be accommodated in various shells. The vertical columns in a periodic table are called groups. Characteristics: The elements in a group do not have consecutive atomic All the elements in a group have similar
- ChemistryClass 10ICSE
In the modern Periodic Table, why does cobalt with higher atomic mass of 58.93 appear before nickel having lower atomic mass of 58.71 ? (b) Why could no fixed position be given to hydrogen in Mendeleev's periodic table?
(a) In modern periodic table, elements are arranged according to the increasing atomic number. The atomic number of cobalt and nickel is 27 and 28 respectively. Therefore cobalt has higher atomic mass and appears before nickel in the periodic table. (b) Mendeleev’s period law failed to explain the position of hydrogen as it resembles both the properties of group 1 alkali metals and group 17 halogens. Hydrogen reacts metal to form ionic compounds called hydrides and also with non
- ChemistryClass 10ICSE
Why does the size of the atoms progressively become smaller when we move from sodium (Na) to chlorine (Cl) in the third period of the periodic table? (b) Helium and neon are unreactive gases. What, if anything, do their atoms have in common?
(a) On moving from sodium to chlorine in the third period, the size of the atoms decreases because of the increase in the atomic number of the elements. The number of electrons and protons in the atoms also increases. As the positive charge increases on the nucleus, the outermost electrons are held even tighter and therefore size of the atom decreases. (b) The atoms of helium and neon have their valence shell completely filled with electrons. The number of valence electron is 8. So th
- ChemistryClass 10ICSE
How does the tendency to lose electrons change as we go down in group 1 of the periodic table? Why does it change this way? (b) How does the tendency to gain electrons change as we go down in group 17 of the periodic table? Why does it change this way?
(a) In group 1, from moving top to bottom the tendency to lose electrons increases due to the addition of shell at each step and atomic radius increases. As the size of atom increases, the distance between the nucleus and valence electrons increases. (b) ) In group 17, from moving top to bottom the tendency to gain electrons decreases due to the addition of shell at each step and atomic radius increases. As the size of the atom goes on increasing, it becomes difficult for the nucleus
- ChemistryClass 10ICSE
How does the atomic size vary on going down from top to bottom in a group of the periodic table? Why does it vary this way? (b) Lithium, sodium and potassium are all metals that react with water to liberate hydrogen gas. Is there any similarity in the atoms of these elements? Explain your answer.
(a) Atomic size increases on going down in a group of the periodic table and when moving top to bottom shell is added at each step due to the size of the atom increases. (b) Yes, the atoms of all the three elements lithium, sodium and potassium have one electron in their outermost shells.
- ChemistryClass 10ICSE
What is the main characteristic of the last elements in the periods of the periodic table ? What is the general name of such elements? (b) What is the number of elements in: (a) 1st period, and (b) 3rd period, of the modern periodic table?
(a) The main characteristic of last elements in a period is that they all have 8 valence electrons in their atoms except helium. Such elements are generally called noble elements which have stable electronic configuration. (b) (i)On first period = 2 (ii) On 3rd period= 8.
- ChemistryClass 10ICSE
What is the usual number of valence electrons and valency of group 18 elements of the periodic table? (a) What happens to the number of valence electrons in the atoms of elements as we go down in a group of the periodic table?
Usual number of valence electrons is 8 of group 18 in periodic table; Valency is The number of valence electrons remains the same in the atom of elements as we go down in a group of the periodic table.
- ChemistryClass 10ICSE
What is the fundamental difference in the electronic configurations between the group 1 and group 2 elements ? (b) On the basis of electronic configuration, how will you identify? (i) Chemically similar elements? The first element of a period?
Group 1 elements have 1 valence electron in their atoms whereas group 2 elements have 2 valence electrons in their atoms. Eg: Lithium, sodium on group 1 have valency 1, Beryllium and magnesium have valency 2 belongs to group 2. (b)(b) (i) All the chemically similar elements will have same valence electrons. (ii) The 1st element of every period has 1 valence electron. Thus it is determined by the number of valence electrons in its atom.
- ChemistryClass 10ICSE
How does the electropositive character of elements change on going down in a group of the periodic table? (b) State how the valency of elements varies (i) in a group, and (ii) in a period, of the periodic table.
(a) The electropositive character of elements increases on going down the group of the periodic table (b) (i) Valency of the elements remains same along the group (ii) The valency of element first increases from 1 to 4 and then decreases to zero on moving from left to right across the period.
- ChemistryClass 10ICSE
How does the size of atoms (atomic size) generally vary in going from left to right in a period of the periodic table? Why does it vary this way? (b) What happens to the metallic character of the elements as we move from left to right in a period of the periodic table?
As we go from left to right across the period atomic size decreases gradually atomic number increases. The proton and electron number increases and due to the large positive charges on nucleus electron has been pulled inside more closer and thus size of the atom decreases. The metallic character of the element decreases as we move from left to right in a
- ChemistryClass 10ICSE
What is a period in a periodic table? How do atomic structures (electron arrangements) change in a period with increase in atomic numbers from left to right? (b) How do the following change on going from left to right in a period of the periodic table? (i) Chemical reactivity of elements (ii) Nature of oxides of elements Give examples in support of your answer.
(a) A period is a horizontal row of elements in aperiodic table. As the atomic number increases from left to right, the size of the atom increases. (b)(i) On moving from left to right in a period of the periodic table the chemical reactivity first decreases and then increases. For example:In the 3rd period of elements, sodium is a very reactive element, magnesium is less reactive whereas aluminium is still less reactive. Silicon is the least reactive in the third period. Now,
- ChemistryClass 10ICSE
An element X belongs to group 2 and another element Y belongs to group 15 of the periodic table: (a) What is the number of valence electrons in X? (b) What is the valency of X? (c) What the number of valence electrons in Y? (d) What is the valency of Y? Explain how you have arrived at your answers.
For groups 1 and 2, the number of valence electrons is equal to the group number. Valency is determined by the number of valence electrons present in the atom of the element. For groups 13 to 18, the number of valence electrons is equal to (group no. - 10). The number of electrons lost or gained by one atom of an element to achieve the nearest inert gas configuration, gives us the valency.
- ChemistryClass 10ICSE
Nitrogen (atomic number 7) and phosphorus (atomic number 15) belong to group 15 of the periodic table. Write the electronic configurations of these two elements. Which of these will be more electronegative? Why?
Electronic configuration:N (2,5) ; P (2, 8, 5) Nitrogen will be more electronegative because its atom has small size due to which the attraction of its nucleus for the incoming electron is more.
- ChemistryClass 10ICSE
Fill in the blanks in the following statements: (a) The horizontal rows in a periodic table are called . (b) In going across a period (right to left) in periodic table, the atomic size of the atom . (c) On moving from right to left in the second period, the number of valence electrons . (d) On going down in a group in the periodic table, the metallic character of elements . The tendency to gain an electron on moving down in a group of the periodic table.
Solution: Periods Increases Decreases Increases Decreases
- ChemistryClass 10ICSE
Rewrite the following statements after correction, if necessary: (i) Elements in the same period have equal valency The metallic character of elements in a period increases gradually on moving from left to right.
Elements in the same group have equal The metallic character of elements in a period decreases gradually on moving from left to
- ChemistryClass 10ICSE
Arrange the following elements in the increasing order of their metallic character: Mg, Ca, K, Ga
Metallic character increases according to this order Ga< Mg <Ca< K.
- ChemistryClass 10ICSE
Arrange the following elements in increasing order of their atomic radii : Li, Be, F, N
Atomic radii increases according to the order F < N < Be < Li.
- ChemistryClass 10ICSE
How do electronic configurations of elements change in second period of periodic table with increase in atomic numbers?
Elements Li(3) Be(4) B(5) C(6) N(7) O(8) F(9) Ne(10) Electronic configuration 2,1 2,2