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Periodic Classification of Elements : Practice Questions


1 Mark Questions

 

1.  Write two reasons responsible for late discovery of noble gases.


2.  Write the valency and usual number of valence electrons of group 18 of the Periodic Table.


3.  Name the most metallic and most non- metallic elements in the Periodic Table.


4.  Mention the type of compounds formed between group 1 and group 17 elements.


5.  How many horizontal rows are there i the Modern Periodic Table and what are they called


6.  Modern Periodic Table, name the metals among the first ten elements.


7.  If an element X is placed in group 14, what will be the  formula and the nature of bonding of its chloride ?


8.  Give one example each of :

(i) Halogen

(ii) Alkali metals


9.  What is meant by periodicity in properties of elements with reference to Periodic Table ?


10.  Size of sodium atom is bigger than that of hydrogen atom. Why ?


11.  What is the similarity in the valency of all the elements of group 1 in the Modern Periodic Table ?


12. Write the electronic configuration of the element which belongs to second period and third group of the Periodic Table.


13.  Out of two elements potassium and sodium, which one can lose electron easily ? Give reason for your answer.


14.  How many shells are present in the elements of the second period ?


15.  Atomic radius of hydrogen is 37 pm. Express it in meters.


16.  An element 'X' forms a chloride with formula XCl3. The element 'X' would most likely be in the same group of the Periodic Table is Na, Mg, Al or Ca ?


17.  An element 'X' is in second period and group 16 of the Periodic Table. Is it metal or non - metal ? Give reason for your answer.


18.  Mention the common name give to the following elements :

Boron, Silicon, Germanium, Arsenic, Antimony.

State their one property that justifies their name.


19.  State the place of metalloids in the Periodic Table.


20.  Name the element which has twice as many electrons in its second shell as in its first shell. Write its electronic configuration also.


21.  Why are isotopes of an element having different atomic masses placed at the same position in the Periodic Table ?


22.  Elements A, B, C and D have atomic numbers 1, 8, 11 and 19 respectively. Choose the odd element and give reason for your answer.


23.  Account for the following :

Elements of group 17 are monovalent.


24.  Why do all the elements of the same period have different properties ?


25.  Account for the following :

Elements of group 18 are called zerovalent.

 

Solutions

 

1.  - Noble gases are very inert.

- They are present in extremely low concentrations in our atmosphere.


2.  - Valency – 0

- No. of valence electrons – 8


3.  - Most metallic element – Francium (Fr)

- Most non - metallic element – Helium (He)


4.  Ionic compounds.


5.  There are 7 horizontal rows in the Modern Periodic Table. These are called periods.


6.  Lithium (Li) and beryllium (Be).


7.  - XCl4

- Ionic bonds.


8.  (i) Chlorine (Cl)

(ii) Sodium (Na)


9.  The repetition of the properties of elements after regular intervals, when the elements are arranged in the order of their increasing atomic numbers, is called periodicity.


10.  Atomic size increases down the group as new shell are added.


11.  Valency is same i.e., 1.


12.  K   L

.      2    3


13.  Potassium, because the tendency to lose electron goes on increasing as we down the group.


14.  Two shells (K and L).


15.  1 pm = 10–12 m

Therefore, Atomic radius = 37 × 10–12 m


16.  Al.


17.  Non - metal because its atomic number is 16. So, electronic configuration will be 2, 8, 6 i.e., it can gain two electrons.


18.  All are metalloids. They have both the properties of metals as well as non - metals.


19.  Metalloids have been placed in the middle of the Periodic Table.


20.  - Carbon

- Electronic configuration : K  L

.                                               2  4


21.  All isotopes of an element have same number of protons and they have same atomic number. So, they can be put in one place.


22.  Odd element : B having atomic number 8.

Reason : B has six electrons in valence shell but A, C and D have one electron in their valence shells.


23.  Group 17 elements e.g., F, Cl, Br and I have seven valences electrons. By gaining one electron, they achieve inert gas configuration. Hence, they are called monovalent.


24.  All the elements of the same period have different properties because they have different number of valence electrons.


25.  Elements of group 18 have completely filled outermost shells and have no tendency to gain or lose electrons. So, they are called zerovalent.



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