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

Question # 1

d and f block elements are called transition elements.Give reasons.

Ans 1: d and f block elements are located in between s and p block elements in the periodic table.Their properties are also in between s and p block elements and they vary from left to the right.It means that their properties show a transition in a systematic way.In d block elements d-d transition occur and elements exhibit colors. Similarly in f block elements d and f orbital show transition of elements hence these are called inner transition elements.That is why they are called as transition elements.

Question # 2

Why the metals are good conductors?

Ans 1: Metal are good conductors due to the presence of relatively loose electrons in the outermost shell of the element and ease of their movement in the solid lattice.

Question # 3

How this confusion is removed in the Modem Periodic Table?

Ans 1: Removal of confusion:Zn,Cd,Hg were placed in a single vertical group,while according to their properties they belonged to two different categories.The same was true for so many other elements placed in the same vertical group in two types of vertical groups,A and B.In modern periodic table,Be,Mg,Ca,Sr and Ba are placed in group IIAand Zn,Cd,Hg in group IIB.

Question # 4

Write a note on blocks in periodic table.

Ans 1: Blocks in periodic table:Elements in the periodic table can be classified into four blocks,this classification is based upon the valence orbital of the elements involved in chemical bonding.According to this classification,Elements of IA and IIA subgroup are called s-block elements.The elements for IIA to VIIIA subgroup are known as p-block elements as their valence electrons are present in p orbital.Similarly in transition elements,electrons are in d orbital are responsible for their valency hence they are called d-block elements.For Lanthanides and Actinides valence electrons are present in f orbital hence these elements are f-block elements.

Question # 5

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

Ans 1: Energy usually released when electronegative elements absord the first electron and E.A in such case is expressed in negative figure,as in the case of halogens.
When a second electron added to a uni-negative ion,the incoming electron is repelled by the already present negative charge and energy is absorbed in the process.
Ans 2: O+e^--------->O^-E.A=-141 kj mole^-1
O^-+e^-------->O^-2E.A₂=+780 kj mole^-1

Question # 6

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 # 7

What is Newland's law of octaves?

Ans 1: Newland who was English chemist,in 1864,classified 62 elements,known at that time,in increasing order of their atomic masses.He noted that every eight element had some properties in common with the first one.The principle on which this classification is based was called the law of Octaves.

Question # 8

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.

Question # 9

Define electron affinity.Give its trend in periodic table.

Ans 1: Electron affinity:Energy released or absorbed,when an electron is added to a gaseous atom to form a negative ion is called electron affinity.
Ans 2: Trend of electron affinity in periodic table:Electron affinity generally increases with increasing atomic number within a period and decreases from lighter to heavier elements in a given group of the periodic table.

Question # 10

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

Ans 1: The removal of electrons causes an imbalance in proton-electron ratio.Due to greater attraction of the nuclear charge,the remaining electrons of the ion are drawn closer to the nucleus.thus,a positive ion is always smaller than the neutral atom from which it is derived.The radius of Na is 157 pm and the radius of Na is 95 pm.

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

d and f block elements are called transition elements.Give reasons.

Why the metals are good conductors?

How this confusion is removed in the Modem Periodic Table?

Write a note on blocks in periodic table.

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

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

What is Newland's law of octaves?

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

Define electron affinity.Give its trend in periodic table.

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

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

d and f block elements are called transition elements.Give reasons.

Why the metals are good conductors?

How this confusion is removed in the Modem Periodic Table?

Write a note on blocks in periodic table.

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

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

What is Newland's law of octaves?

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

Define electron affinity.Give its trend in periodic table.

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

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

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

Why do metals conduct electricity?

How melting and boiling points varied in a period?

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

What is lanthanide contraction?

Why 1stelectron affinity is negative and 2ndis positive?

How the classification of elements in different blocks help in understanding their chemistry?

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

What is Dobereiner's Law of triads?

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

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

Why do metals conduct electricity?

Why melting and boiling points of elements belonging to groups VA-VIIA are lower?

What is Newland's law of octaves?

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

Why 1stelectron affinity is negative and 2ndis positive?

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

Why the ionization energies decreases down the groups?

Write a note on blocks in periodic table.

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

How this confusion is removed in the Modem Periodic Table?

12th Class Chemistry Chapter 1 Preparation

Is this page helpful?

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

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

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

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

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