Lakhmir singh solutions chemistry class 10 Solutions for Chapter 5 chapter 5 periodic classification of elements

(b) How were the positions of cobalt and nickel resolved in the modern periodic table?

(a) How were the positions of isotopes of an element decided in the modern periodic table?

(b) What is the significance of atomic number in the modern classification of elements? Explain with the help of an example.

(a) In the modem periodic table, which are the metals among the first ten elements?

(c) Give two examples each of (i) group 1 elements (ii) group 17 elements (iii) group 18 elements.

(b) How many periods and groups are there in the long form of periodic table?

(a) What is meant by (i) a group, and (it) a period, in a periodic table?

Fill in the following blanks with suitable words:

(a) The basis for modern periodic table is ______.

(b) The horizontal rows in a periodic table are called ______.

(c) Group 1 elements are called ______.

(d) Group 17 elements are known as ______.

(e) Group 18 elements are called ______.

(f) According to Newlands’ classification of elements, the properties of sulphur are similar to those of oxygen because sulphur is the ______ element starting from oxygen

Which group of elements could be placed in Mendeleev’s periodic table later on, without disturbing the original order? Give reason.

State one example of a Dobereiner’s triad, showing in it that the atomic mass of middle element is half-way between those of the other two.

Name two elements whose properties were predicted on the basis of their positions in Mendeleev’s periodic table.

Name two elements whose properties were predicted on the basis of their positions in Mendeleev’s periodic table.

In the classification of the then known elements, Mendeleev was guided by two factors. What are those two factors?

What was the Mendeleev’s basis for the classification of elements?

X and Y are the two elements having similar properties which obey Newlands’ law of octaves. How many elements are there in-between X and Y?

A, B and C are the elements of a Dobereiner’s triad. If the atomic mass of A is 7 and that of C is 39, what should be the atomic mass of B?

Name the scientists who gave the following laws in the early classification of elements:

(a) Law of octaves (b) Law of triads

The three elements predicted by Mendeleev from the gaps in his periodic table were known as eka-boron, eka – aluminium and eka-silicon. What names were given to these elements when they were discovered later on?

Name the Russian chemist who said that the properties of elements are a periodic function of their atomic masses.

State whether the following statement are true or false:

(a) Newlands divided the elements into horizontal rows of eight element each.

(b) According to Mendeleev’s periodic law, the properties of elements are a periodic function of their atomic numbers.

(c) The elements in a group have consecutive atomic numbers.

(a) On what basis did Mendeleev arrange the element in his periodic table.

(b) On what basis are they arranged now?

Rewrite the following statements after correction, if necessary:

(a) Groups have elements with consecutive atomic numbers.

(b) Periods are the horizontal rows of elements.

(c) Isotopes are the elements of the same group.

(c) Where should hydrogen be placed in the modern periodic table? Give reason for your answer.

(a) On which side of the periodic table will you find metals?

Which of the following statement about modern periodic table is correct?

(a) It has 18 horizontal rows known as periods

(b) It has 7 vertical columns known as periods

(c) It has 18 vertical columns known as groups

(d) It has 7 horizontal rows known as groups

(a) State the periodic law on which Mendeleev’s periodic table was based. Why and how was this periodic law changed ?

(b) Explain why, the noble gases are placed in a separate group.

(b) What chemical properties of elements were used by Mendeleev in creating his periodic table?

The atomic particle whose number in the atoms of an element always remains the same and which forms the real basis for the modern classification of element is:

(a) Electron

(b) Proton

(c) Neutron

(d) Meson

The modern periodic table was prepared by :

(a) Dobereiner

(b) Newland

(c) Bohr

(d) Mendeleev

An element X forms an oxide X₂O₃. In which group of Mendeleev’s periodic table is this element placed?

(a) Group II

(b) Group III

(c) Group V

(d) Group VIII

Which of the following statement is correct in regard to the classification of elements ?

(a) Elements in the periodic table are arranged on the basis of increasing atomic masses

(b) Elements in Mendeleev’s periodic table are arranged on the basis of increasing atomic numbers

(c) In modern periodic table, the element nickel of lower atomic mass is kept before the element cobalt of higher atomic mass

(d) In modern periodic table, the isotopes of chlorine having diffrenet atomic masses are kept in the same group.

The atomic numbers of four elements P, Q, R and S are 6, 18, 14 and 16 respectively. Out of these, the element known as metalloid is:

(a) P

(b) Q

(c) R

(d) S

In Mendeleev’s periodic table, gaps were left for the elements to be discovered later on. An element which found a vacant place in the periodic table later on is:

(a) Be

(b) Si

(c) Ge

(d) Se

The three elements having chemical symbols of Si, B and Ge are:

(a) All metals

(b) All non-metals

(c) All metalloids

(d) Si is metalloid and Ge is non-metal

According to Mendeleev’s periodic law, the elements were arranged in the periodic table in the order of:

(a) Decreasing atomic numbers

(b) Increasing atomic numbers

(c) Decreasing atomic masses

(d) Increasing atomic masses

The Newland’s law of octaves for the classification of elements was found to be applicable only up to the element:

(a) Potassium

(b) Calcium

(c) Cobalt

(d) Phosphorus

In Mendeleev’s periodic table, gap was not left for one of the element. This element is:

(a) Gallium

(b) Beryllium

(c) Germanium

(d) Scandium

(e) Name the scientist who prepared modern periodic table.

(d) Is it possible to have an element having atomic number 1.5 placed between hydrogen and helium ?

(c) How could the modern periodic law remove various anomalies of Mendeleev’s periodic table? Explain with examples.

(b) How does the electronic configuration of the atom of an element relate to its position in the modern periodic table?

(a) State modern periodic law.

(e) Which group of elements was missing from Mendeleev’s original periodic table?

(d) Besides gallium, which two other elements have since been discovered for which Mendeleev had left gaps in his periodic table ?

(a) State Mendeleev’s periodic law.

(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? Justify your answer.

(d) In Mendeleev’s periodic table, why was there no mention of noble gases like helium, neon and argon?

(c) Why did Mendeleev leave some gaps in his periodic table?

(b) What were the two criteria used by Mendeleev to classify the elements in his periodic table?

The three imaginary elements X,Y and Z represent a Doberieners triad. If the atomic mass of element X is 14 and that of element Y is 46,then the atomic mass of Element Z will be:

(a) 28

(b) 60

(c) 78

(d) 72

(a) How do the properties of eka – aluminium element predicted by Mendeleev compare with the actual properties of gallium element? Explain your answer.

(b) What names were given by Mendeleev to the then undiscovered elements (i) scandium (ii) gallium, and (iii) germanium?

(a) Why do we classify elements?

(a) State the merits of Mendeleev’s classification of elements.

(c) What were the limitations of Newlands’ law of octaves?

(b) Describe two anomalies of Mendeleev’s periodic classification of elements.

(a) Did Dobereiner’s triads also exist in the columns of Newlands’ law of octaves? Explain your answer.

What is Newlands’ law of octaves? Explain with an example.

What is Dobereiner’s law of triads? Explain with the help of one example of a Dobereiner’s triad.

(a) Name three elements that have a single electron in their outermost shells.

(b) Name two elements that have two electrons in their outermost shells.

(c) Name three elements with completely filled outermost shells.

(c) What is the name of those elements which divide metals and non-metals in the periodic table?

(b) On which side of the periodic table will you find non-metals?

(b) What were the limitations of Dobereiner’s classification of elements?

(c) State any three limitations of Mendeleev’s classification of elements.

(a) 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) 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.

Which of the following element would lose an electron easily?

(a) Mg

(b) Na

(c) K

(d) Ca

Which of the following is the valence shell for the elements of second period of the modern periodic table?

(a) M shell

(b) K shell

(c) L shell

(d) N shell

On moving from left to right in a period in the periodic table, the atomic number of elements increases. What happens to the size of the atoms of elements on moving from left to right in a period?

(a) Increases

(b) Decreases

(c) Remains same

(d) First increases then decreases

Which one of the following does not increase while moving down the group of the periodic table:

(a) Atomic radius

(b) Metallic character

(c) Valence electrons

(d) Shells in the atoms

The element which form a basic oxide has the atomic number of:

(a) 18

(b) 17

(c) 14

(d) 19

The element which can form an acidic oxide should be the one whose atomic number is:

(a) 6

(b) 16

(c) 12

(d) 19

The correct formula of the oxide of Eka-aluminium element predicted by Mendeleev’s was:

(a) EaO₃

(b) Ea₂O₂

(c) Ea₂O₃

(d) EaO

Which of the following are the correct characteristics of isotopes of an element?

(i) Same atomic mass

(ii) Same atomic number

(iii) Same physical properties

(iv) Same chemical properties

(a) (i), (iii) and (iv)

(b) (ii), (iii) and (iv)

(c) (ii) and (iii)

(d) (ii) and (iv)

The atomic numbers of the elements Na, Mg, K and Ca are 11, 12, 19 and 20 respectively. The element having largest atomic radius is:

(a) Mg

(b) Na

(c) K

(d) Ca

The element which has the maximum number of valence electron is:

(a)Na

(b) P

(c) Si

(d) Al

Which of the following set of elements is written correctly in the order of their increasing metallic character?

(a) Mg, Al, Si

(b) C, O, N

(c) Na, Li, K

(d) Be, Mg, Ca

Where would you locate the element with electronic configuration 2, 8 in the modern periodic table?

(a) Group 8

(b) Group 2

(c) Group 18

(d) Group 10

Which of the following element not lose an electron easily?

(a) Na

(b) F

(c) Mg

(d) Al

An element which is an essential constituent of all organic compounds belongs to following group of modern periodic table:

(a) Group 4

(b) Group 14

(c) Group 15

(d) Group 16

Five elements A, B, C, D and E have atomic numbers 2, 3, 7, 10 and 18 respectively. The elements which belong to the same period of the periodic table are:

(a) A, B, C

(b) B, C, D

(c) A, D, E

(d) B, D, E

The atomic number of an element is 20. In modern periodic table, the element is placed in:

(a) 2^nd period

(b) 4^th period

(c) 3^rd period

(d) 1^st period

The electronic configuration of the atom of an element X is 2, 8, 4. In modern periodic table, the element X is placed in:

(a) 2^nd group

(b) 4^th group

(c) 14^th group

(d) 8^th group

Which of the following is not correct statement about the trends when going from left to right across the periods of the periodic table?

(a) The elements become less metallic in nature

(b) The number of valence electrons increases

(c) The atom lose their electrons more easily

(d) The oxides become more acidic

(a) 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.

(e) What are the advantages of the periodic table?

(a) 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:

(d) State one reason for keeping fluorine and chlorine in the same group of the periodic table.

(e) What are the merits of the modern periodic table of elements?

(a) 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:

(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.

(a) 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) 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?

The elements A, B, C, D and E have atomic numbers 9, 11, 17, 12 and 13 respectively. The pair of elements which belongs to the same group in the periodic table is:

(a) A and B

(b) B and D

(c) A and C

(d) D and E

(a) 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) What is the usual number of valence electrons and valency of group 18 elements of the periodic table?

(b) What happens to the number of valence electrons in the atoms of elements as we go down in a group of the periodic table?

(a) 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?

(ii) The first element of a period?

(a) 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) Explain why:

(i) All the elements of a group have similar chemical properties.

(ii) All the elements of a period have different chemical properties.

(b) The atomic radii of three elements X, Y and Z of a period of the periodic table are 186 pm; 104 pm and 143 pm respectively. Giving a reason, arrange these elements in the increasing order of atomic numbers in the period.

(a) 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?

(a) 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?

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.

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?

The correct increasing order of the atomic radii of the elements oxygen, fluorine and nitrogen is:

(a) O, F, N

(b) N, F, O

(c) O, N, F

(d) F, O, N