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Karnataka SSLC Class 10 Science Solutions Chapter 5 Periodic Classification of Elements
KSEEB SSLC Class 10 Science Chapter 5 Intext Questions
Text Book Part II Page No. 25
Did Dobereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out.
Yes, Dobereiner’s triads also exist in the columns of Newlands’ Octaves. One such column is Li, K, Na.
What were the limitations of Dobereiner’s classification?
Limitation of Dobereiner’s classification:
All known elements could not be classified into groups of triads on the basis of their properties.
What were the limitations of Newlands’ Law of Octaves?
Limitations of Newlands’ law of octaves:
- It was not applicable throughout the arrangements. It was applicable up to calcium only. The properties of the elements listed after calcium showed no resemblance to the properties of the elements above them.
- Elements discovered after Newlands’ octaves did not follow the law of octaves.
- The position of cobalt and nickel in the group of the elements (F, Cl) of different properties could not be explained. Similarly, properties of iron also could not be explained.
Text Book Part II Page No. 29
Use Mendeleev’s Periodic Table to predict the formulae for the oxides of the following elements:
K, C, AI, Si, Ba.
- K belongs to group 1. Therefore, the oxide will be K2O.
- C belongs to group 4. Therefore, the oxide will be CO2.
- Al belongs to group 3. Therefore, the oxide will be Al2O3.
- Si belongs to group 4. Therefore, the oxide will be SiO2.
- Ba belongs to group 2. Therefore, the oxide will be BaO.
Besides gallium, which other elements have since been discovered that were left by Mendeldev in his Periodic Table? (any two)
Scandium and Germanium.
What were the criteria used by Mendeleev in creating his Periodic Table?
Mendeleev considered the atomic mass of the elements as the unique criteria of the elements. He proposed that the chemical properties of elements are the periodic function of their atomic masses. And thus, he arranged the elements in the increasing order of their atomic masses.
Why do you think the noble gases are placed in a separate group?
Noble gases are very inert and they are different when compared to other elements. Hence, these are placed in separate group.
Text Book Part II Page No. 34
How could the Modern Periodic Table remove various anomalies of Mendeleev’s Periodic Table?
Various anomalies of Mendeleev’s Periodic Table are removed in the Modern Periodic Table as follows:
- Elements are arranged in the increasing order of their atomic number in Modern Periodic Table, thus one element is placed in one position.
- In Modern Periodic Table, there was no problem with the place of isotopes, as isotopes have the same atomic mass with different atomic numbers.
- Elements having the same valence electrons are kept in the same group.
- Elements having the same number of shells were put under the same period.
- Position of hydrogen became clarified as it is kept in the group with the elements of same valence electrons.
Name two elements you would expect to show chemical reactions similar to magnesium. What is the basis for your choice?
Calcium and strontium are the two elements we would expect to show chemical reactions similar to magnesium. Because these resemble magnesium in chemical properties, All three elements have two valence electrons.
(a) three elements that have a single electron in their outermost shells.
(b) two elements that have two electrons in their outermost shells.
(c) three elements with filled outermost shells.
(a) Lithium, sodium and potassium are the 3 elements which have single electron in their outermost orbit.
(b) Magnesium and calcium are the two elements which have 2 electrons in their outermost orbit.
(c) Noble gases such as Helium, Neon and Argon are the three elements whose outermost shells are completely filled.
Lithium, sodium, potassium are all metals that react with water to liberate hydrogen gas. Is there any similarity in the atoms of these elements? Helium is an unreactive gas and neon is a gas of extremely low reactivity. What, if anything, do their atoms have in common?
Yes. The atoms of all the three elements lithium, sodium and potassium have one electron in their outermost shells. Both helium (He) and neon (Ne) have filled outermost shells. Helium has a duplet in its K shell, while neon has an octet in its L shell.
In the Modern Periodic Table, which are the metals among the first ten elements?
Among the first ten elements, Lithium (Li) and Beryllium (Be) are metals.
By considering their position in the Periodic Table, which one of the following elements would you expect to have maximum metallic characteristic?
Ga Ge As Se Be
Berylium has maximum metallic characteristic.
KSEEB SSLC Class 10 Science Chapter 5 Textbook Exercises
Which of the following statements is not a correct statement about the trends when going from left to right across the periods of Periodic Table.
(a) The elements become less metallic in nature.
(b) The number of valence electrons increases.
(c) The atoms lose their electrons more easily.
(d) The oxides become more acidic.
(c) The atoms lose their electrons more easily.
Element X forms a chloride with the formula XCl2, which is a solid with a high melting point. X would most likely be
in the same group of the Periodic Table as
Which element has
(a) two shells, both of which are completely filled with electrons?
(b) the electronic configuration 2, 8, 2?
(c) a total of three shells, with four electrons in its valence shell?
(d) a total of two shells, with three electrons in its valence shell?
(e) twice as many electrons in its second shell as in its first shell?
(a) What property do all elements in the same column of the Periodic Table as boron have in common?
(b) What property do all elements in the same column of the Periodic Table as fluorine have in common?
(a) All elements in Boron group have valency 3.
(b) All elements in fluorine group have valency 1.
An atom has electronic configuration 2, 8, 7.
(a) What is the atomic number of this element?
(b) To which of the following elements would it be chemically similar? (Atomic numbers are given in parentheses.)
N(7) F(9) P(15) Ar(18)
(a) Atomic Number is 17.
(b) N and P are chemically similar.
The position of three elements A, B and C in the Periodic Table are shown below –
(a) State whether A is a metal or non-metal.
(b) State whether C is more reactive or less reactive than A.
(c) Will C be larger or smaller in size than B?
(d) Which type of ion, cation or anion, will be formed by element A?
a) A is a Non metal.
b) C is less reactive comparing to A.
c) C is smaller in size comparing to A.
d) Cation is formed by A.
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? Why?
Nitrogen (7): 2,5
Phosphorus (15): 2, 8, 5.
Since electronegativity decreases with moving from top to bottom in a group, thus nitrogen will be more electronegative.
How does the electronic configuration of an atom relate to its position in the Modern Periodic Table?
In the modern periodic table, elements having some electronic configuration are arranged in the same group.
In the Modern Periodic table, calcium (atomic number 20) is surrounded by elements with atomic numbers 12, 19, 21 and 38. Which of these have physical and chemical properties resembling calcium?
Atomic number 12 = 2, 8, 2
Atomic number 20 = 2, 8, 8, 2
Atomic Number 19 = 2,8, 8, 1
Atomic number 21 = 2, 8, 9, 2
Atomic number 38 = 2, 8, 18, 8, 2
Calcium will have similar physical and chemical properties as element with atomic numbers 12 and 38.
Compare and contrast the arrangement of elements in Mendeleev’s Periodic Table and the Modern Periodic Table.
Mendeleev s Periodic table:
- Elements are arranged in the increasing order of their atomic mass.
- This table has 8 groups and 6 periods. And each group is subdivided as an A and B.
- In this table, Hydrogen has no position.
- No position for isotopes, because in Mendeleev period these are not discovered.
Modern Periodic table:
- Elements are arranged in the increasing order of their atomic number.
- It has 18 groups and 7 periods.
- Inert gases are placed in separate groups.
- In this table, a zigzag line separates Metals from Non-metals.
Mendeleev’s Periodic table vs Modern Periodic table:
- Elements are arranged in the increasing order of their atomic masses, while in Modern Periodic table elements are arranged in the increasing order of their atomic numbers.
- There are a total of 7 groups (columns) and 6 periods (rows) while in Mendeleev’s’ Periodic Table, there are a total of 18 groups (columns) and 7 periods (rows).
- Elements having similar properties were placed directly under one another, while in Mendeleev’s’ Periodic Table elements having the same number of valence electrons are present in the same group.
- In Mendeleev’s Periodic Table the position of hydrogen could not be explained, while in Modern Periodic table hydrogen is placed above alkali metals.
- No distinguishing positions for metals and non-metals in Mendeleev’s Periodic Table while in Modern Periodic Table metals are present at the left-hand side of the periodic table whereas nonmetals are present at the right-hand side.
KSEEB SSLC Class 10 Science Chapter 5 Additional Questions and Answers
Fill in the blanks:
At present …….. elements are known to us.
Law of triads was given by ……..
……. was introduced by Newlands’
Law of Octaves.
…….. was the most important contributor to the early development of a periodic table.
When Mendeleev started his work ……. elements were known.
Hydrogen combines with metals and non-metals to form ………
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