Chapter-3
Periodic Classification of Elements
Learning Card-1
1. State law of Modern Periodic Table.
The properties of elements are periodic functions of their atomic numbers
2. Give an example for dobereiner’s Traid
Element - Atomic mass
Chlorine - 35.5
Bromine - 80
Iodine - 127
3. Why 18th group elements are called noble gases?
Octet structure or O (zero) valency
4. What are periods & group in the mendeleev periodic table?
Rows in the periodic table are called as periods & Columns as groups.
5. Name the four blocks of modern periodic table.
s-Block, p-Block, d-Block, f-Block
6. Write the electronic configuration of sodium atom.
Atomic Number of Na is 11
1S2, 2S2, 2P6, 3S1
7. What are metalloids? Give an example.
The element which shows both metallic & non-metallic property is a metalloid.
Ex Germanium
8. What are transitional elements? Give an example.
Elements where electrons of their atoms occupy ultimate shells leaving penultimate shell partially vacant are called transitional elements or d- block element.
9. Write three advantages of modern periodic table.
1) Easy to access data of the element.
2) Base on modern electronic configuration & nature of chemical founds.
3) Predict the properties of the elements by considering the position of elements in periodic table.
10. What are Isotopes? Write four Isotopes of carbon.
Elements having same atomic number with different Atomic mass are called Isotopes
6C11, 6C12, 6C13, 6C14
11. The better semiconductor in 14th group element is: -
a) Carbon b) Germanium c) Lead d) silicon
12. In the periodic law the following repeats at regular intervals
a) Atomic Number b) General Properties c)Atomic Mass d)Isotopes
13. The group Number of the element of Neon is.
a) 1 b) 8 c) 9 d) 18
Learning Card-2
1. State New land’s Law of Octave.
‘‘The periodicity of repetition of properties of elements is eight’’ Hence newland law is given the name octave.
2. How many periods and groups are there in modern periodic table?
There are 7 periods and 18 groups in periodic table.
3. Write one limitation of mendeleev periodic table
Mendeleev considered atomic mass for construction of periodic table, which does not give chances for Isotopes.
4. In a traid of A, B and C elements. If the atomic mass of B&C are 88 & 137, respectively find atomic mass of A.
Solution
Given
B=88
C=137
A=?
B= (A+C)/2
88= (A+137)/2
88x2=A+137
176 = A+137
176-137 = A
39 =A
A = 39
5. Write the name and electronic configuration of element bearing the atomic number 26.
Atomic Number 26 belongs to Iron (Fe)
1S2, 2S2, 2P6, 3S2, 3P6, 3d6, 4S2
6. Why the size of the atoms tend to increase as we go down in a group in periodic table?
Down the group new shell is added to the atom so as we go down in a group in periodic table the size of atom increases.
7. Give an example for each of the following:- 1)- S- block 2)-d- block
H = S- block
Cu = d- block
8. Give two example for 14th group elements.
C & Si are the examples of 14th group elements
9. Define the following 1) Atomic size 2) Ionisation energy.
1) The distance between the centre of an atom and its outer most shell is taken as atomic size to imagine the three dimensional size of atom.
2) Ionisation energy is the energy required to remove the electron from outer most shell from the free and isolated atom of an element
10. List all the members of 18th group elements of periodic table.
He-Helium, Ne-Neon, Ar-Argon, Kr-Krypton, Xe-xenon, Rn-Radon
11. An Example of transitional element is.
a) Li b) Al c) Ni d) Cl
12. The following is a metalloid
a) Uranium b) Sodium c) Cadmium d) Germanium
Learning Card-3
1. Why block‘d’ elements are called transitional elements?
Elements where electrons of their atoms occupy ultimate shells leaving penultimate shells partially vacant are called Transitional elements
2. Why the atomic number is more useful than atomic mass to classify the elements?
Atomic number gives the number of protons or electrons in an atom, which determine the physical and chemical properties, not atomic mass.
3. Give any reason for Newland’s law of octave’s failure.
It was not possible to extend the law after seventeenth elements
4. Name the group which have the complete similarity?
Group No 17
5. Atomic number of Aluminum is 13. Find its position in periodic table with help of electronic configuration.
1S2, 2S2, 2P6, 3S2, 3P1, 3rd period 13th group
6. Name any two ‘f’ block elements.
Uranium, Plutonium, Thorium or any two.
7. Sodium is electropositive. Verify.
Atomic No of Sodium is 11, so No proton(+)11, No electrons (-)11, electronic configuration is
1S2, 2S2, 2P6, 3S1,
8. “Atomic size decreases across the period” .Give reason.
Along a period there will be not be any change in the number of shells, but more electrons are added to the same shell and the nucleus exerts greater inward pull on the electrons. Hence the atomic size decreases.
9. In the first period Hydrogen and helium are not placed adjacent to each other. Give reasons.
Outer most shell of Helium Atom is filled with electrons to the maximum capacity, Hence it the valency of this element is zero. Hence it is place in Zero group.
10. Sate the “law of triads” verify the law of the trade using the following elements.
Element -Atomic mass
Chlorine - 35.5
Bromine - 80
Iodine - 127
Three elements having similar properties and arranged them in increasing order of atomic mass. Average mass of first and third element is almost similar to that of second elements.
11. In a trial of “A” “B” and “C” elements, If the atomic mass of “A” “B” and “C” are 150 and 200 respectively, the atomic mass of “A” is
a) 100 b) 125 c) 250 d) 300
12. In a periodic table of 18th group in general
a) Form Ionic bond b) form covalent bond c) form hydrogen fond d) do not form bond.
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