PERIODIC CLASSIFICATION OF ELEMENTS

Name: Assignment - III Class: X Subject: Chemistry

PERIODIC CLASSIFICATION OF ELEMENTS


I Choose the correct answer

1. In Dobereiner triad, the atomic weight of middle element is ( )
(a) The sum of atomic weights of first and third elements.
(b) The product of the atomic weight of first and third elements.
(c) The ratio of the atomic weights of first and third elements.
(d) The mean of the atomic weights of first and third elements.
2. The first classification of elements is attempted by ( )
(a) Bohr (b) Mosley (c) Mendeleef (d) Dobereiner.
3. The number of columns present in modern periodic table. ( )
(a) 15 (b) 16 (c) 17 (d) 18
4. Mendeleef’s periodic table is based on ( )
(a) Atomic volume (b) Atomic radius (c) Atomic weight (d) Atomic number
5. Mosley’s periodic table is based on ( )
(a) Atomic volume (b) Atomic radius (c) Atomic weight (d) Atomic number
6. The number of elements present in the first period are ( )
(a) 8 (b) 2 (c) 18 (d) 36
7. The incomplete period is ( )
(a) 7 (b) 6 (c) 1 (d) 2
8. The ionization potential in a group from top to bottom ( )
(a) Decreases (b) Increases (c) Remains same (d) Shows irregular trend
9. The atomic radius is measured in ( )
(a) eV (b) kJ/mole (c) kcal/mole (d) Angstrom

II Fill in the blanks

1. The earliest classification of elements is due to _____________________ in 1817.
2. Law of octaves was proposed by _____________________
3. Lother Meyer, proposed the periodic law based on the _______________ of elements.
4. Mendeleef arranged the elements in the increasing order of their _________________
5. The periodic table proposed by Mosley is known as _______________________
6. Mosley’s periodic law states that ‘the properties of the elements are the periodic function of their _____________________.





7. The chemical similarity of elements in a group is due to their similar _____________ electronic configuration.
8. Each period starts with ________________ and ends with ______________ elements.
9. Inert gases are the elements having _________________ electronic configuration.
10. Elements of s-block and p-block put together are known as ____________________
11. All types of elements, viz., metals, metalloids, non metals are placed in ________________
12. In a group the atomic radius ______________ from top to bottom.
13. In a group the EN __________________ from top to bottom.
14. EN of inert gases is __________________
15. The oxidizing power in a group _______________ and in a period _______________
16. The reducing power in a group _______________ and in a period________________

III 1 Mark questions

1. What is a triad?
A. A set of three elements arranged in the increasing order of their atomic weights is called a triad.
2. Give examples of three Dobereiner triads.
A. Cl, Br, I; S, Se, Te,; Li, Na, K; Fe, Co, Ni are the different triads arranged by Dobereiner.
3. What is Newland’s concept of octaves?
A. According to law of octaves, if the elements are arranged in the increasing order of their atomic weights, the properties of eight elements is a kind of repetition of the first one like the 8th note of an octave in music.
4. State Mendeleef’s periodic law.
A. Mendeleef’s periodic law states that ‘the properties of the elements are the periodic function of their atomic weights’.
5. Name the inert gases.
A. He, Ne, Ar, Kr, Xe, Rn are the inert gas elements.
6. Write the general electronic configuration of inert gases.
A. ns2, np6 is the general electronic configuration of inert gases.
7. What are inner transition elements?
A. Lanthanides and actinides (f-block elements) are called inner transition elements.
8. Define atomic radius.
A. The distance between the centre of the nucleus and the outermost oribital is defined as atomic radius (or) atomic size.






9. Define second ionization energy.
A. The minimum energy required to remove an electron from the outermost orbital of unipositive ion is defined as second ionization energy.
10. Define electronegativity
A. The tendency of a bonded atom in a molecule to attract the electron density of the shared pair of electrons is called as electronegativity
11. Define electropositive character
A. The tendency (or ability) of an atom to lose the valence electrons and become +vely charged ion is called electropositive character (or) metallic character.
12. Which group of the elements have highest electropositive character?
A. IA group elements have highest electropositive character.
13. Define oxidation and reduction.
A. Oxidation: Addition of oxygen to a given compound (or) removal of hydrogen from a given compound is called oxidation.
Reduction: Addition of hydrogen to a given compound (or) removal of oxygen from a given compound is defined as reduction.
14. Which group of elements can be used as oxidizing and reducing agents?
A. Oxidizing agents: VII A group-elements can be used as oxidizing agents.
Reducing agents: IA and IIA group elements can be used as reducing agents.

IV 4 Marks questions

1. How does the atomic radius vary in a period and in a group?
2. Explain the variation of ionization energy in a group?
3. Write about the salient features and draw backs of Mendeleef’s periodic table.
4. What re the features of long form of periodic table? (or) what are the salient features of Mosley’s periodic table?