12th Class Chemistry Chapter 1 Periodic Classification of Elements and Periodicity Short Questions Preparation

Question # 1

M.P and B.P of short periods increase up to middle of period and then decreases.Why?

Ans 1: Melting and boiling points of short periods:Across the short periods,the melting and boiling points of elements increase with the number of valance electrons up to group IVA and then decrease up to the noble gases.The melting points of groups IA element are low because each atom in them provides only one electron to for a bond with other atom.Melting point of group IIA elements are considerable higher than those of group IA elements because each atom in them provides two binding electrons.

Question # 2

Solution of Na₂O in water is alkaline.Justify the statement.

Ans 1: Alkali metal oxides dissolve in water to give alkaline solutions.For Example:
Na₂O+H₂O------------>2NaOH
Ans 2: The reaction of alkali metal oxide with water is an acid-base reaction.The reaction involved the decomposition of water molecule by an oxide ion as:
O^2-+ H₂O -------->2OH^-

Question # 3

Define modern periodic table.

Ans 1: Modern periodic table:The table of elements in which all the elements are arranged in ascending order of their atomic numbers having seven periods and eighteen groups is called modern periodic table.

Question # 4

Melting points of Group VIIA elements increases down the group.Why?

Ans 1: For elements of group VIIA,which exist in the form of molecules,the melting and boiling points increase down the group.This is because large molecules exert stronger force of attraction due to their higher polarizabilities.

Question # 5

Ionization energy increases from left to right in a period.Justify the statement.

Ans 1: In period by moving from left to right the outer shell remains the same while the nuclear charge increase effectively that makes the removal of an electron difficult and hence the value of ionization energy increases.

Question # 6

Give two defect of Mendeleev's periodic table.

Ans 1: Two defect of Mendeleev's periodic table:
Ans 2: i) It does not explain the position of isotopes.
ii) It does not explain the wrong order of atomic masses of elements.

Question # 7

Why metallic character increases from top to bottom in a group of metals?

Ans 1: Metallic character increases from top to bottom in a group because from top to bottom atomic size of atoms increases and it is easier to remove the electron of an atom bigger in size.

Question # 8

The oxidation state vary in a period,but remain almost constant in a group.Give reason.

Ans 1: The number of electrons in outermost shells goes on changing in periods from left to the right,So oxidation states go on changing.The number of electrons in the outermost shells remains the same in a group,so the oxidation states remains the same.Anyhow,the process of unpairing of electrons may happen in a group and oxidation states may change.

Question # 9

Why the ionization energies decreases down the groups?

Ans 1: Going down in the group,the nuclear charge increases but as the size of the atom and the number of electrons causing the shielding effect also increases therefore ionization energy decreases from top to bottom.

Question # 10

Electrical conductance of metals in group IA generally increases from top to bottom.Explain

Ans 1: The property in mainly due to the presence of relatively loose electrons in the outermost shell of the elements and ease of their movement in the solid lattice.In group IA,generally electrical conductance increases from top to bottom because from top to bottom loosely held electrons are more easily available.

Latest Educational News Stories

Pakistan's Largest Database of Colleges and Universities

BS Programs

University Past Papers

University Results

Exam Results 2024

Study Abroad Programs and Opportunities for Pakistani Students

12th Class Chemistry Chapter 1 Periodic Classification of Elements and Periodicity Short Questions Preparation

Online Short Questions For Chapter 1 "12th Class Chemistry Chapter 1 Short Questions Preparation "

Chemistry - 12th Class Chemistry Chapter 1 Short Questions Preparation

M.P and B.P of short periods increase up to middle of period and then decreases.Why?

Solution of Na2O in water is alkaline.Justify the statement.

Define modern periodic table.

Melting points of Group VIIA elements increases down the group.Why?

Ionization energy increases from left to right in a period.Justify the statement.

Give two defect of Mendeleev's periodic table.

Why metallic character increases from top to bottom in a group of metals?

The oxidation state vary in a period,but remain almost constant in a group.Give reason.

Why the ionization energies decreases down the groups?

Electrical conductance of metals in group IA generally increases from top to bottom.Explain

Prepare Complete Set Wise Questions For Chapter 1 "12th Class Chemistry Chapter 1 Short Questions Preparation "

Set 1

Set 2

Set 3

12th Class Chemistry Chapter 1 Short Questions Preparation - Set 1

M.P and B.P of short periods increase up to middle of period and then decreases.Why?

Solution of Na2O in water is alkaline.Justify the statement.

Define modern periodic table.

Melting points of Group VIIA elements increases down the group.Why?

Ionization energy increases from left to right in a period.Justify the statement.

Give two defect of Mendeleev's periodic table.

Why metallic character increases from top to bottom in a group of metals?

The oxidation state vary in a period,but remain almost constant in a group.Give reason.

Why the ionization energies decreases down the groups?

Electrical conductance of metals in group IA generally increases from top to bottom.Explain

12th Class Chemistry Chapter 1 Short Questions Preparation - Set 2

How do member of group V!-A(except oxygen) show+4 and +6 oxidation state?

Lonic radii of negative ion is always bigger in size than its parent atom.Why?

Why 1stelectron affinity is negative and 2ndis positive?

Melting points of Group VIIA elements increases down the group.Why?

What is Newland's law of octaves?

How this confusion is removed in the Modem Periodic Table?

Why do metals conduct electricity?

Define Metalloid.

Define modern periodic table.

Describe 7th period of modern periodic table.

12th Class Chemistry Chapter 1 Short Questions Preparation - Set 3

Why metallic character increases from top to bottom in a group of metals?

Why the second value of electron affinity of an element is usually shown with a positive sign?

Why 1stelectron affinity is negative and 2ndis positive?

Ionization energy increases from left to right in a period.Justify the statement.

The ionic radius of positive ion is smaller than its parent atom.Give reason.

The oxidation state vary in a period,but remain almost constant in a group.Give reason.

Give two defect of Mendeleev's periodic table.

Ionization energy of Al3+ is greater than Mg2+.Give the reason.

Melting points of Group VIIA elements increases down the group.Why?

Why do metals conduct electricity?

12th Class Chemistry Chapter 1 Preparation

Share your comments & questions here

Solution of Na₂O in water is alkaline.Justify the statement.

Solution of Na₂O in water is alkaline.Justify the statement.

Why 1^stelectron affinity is negative and 2^ndis positive?

Describe 7^thperiod of modern periodic table.

Why 1^stelectron affinity is negative and 2^ndis positive?

Ionization energy of Al³⁺is greater than Mg²⁺.Give the reason.