default_background
✕

Find the best tutors and institutes for Class 11 Tuition

Find Best Class 11 Tuition

Please select a Category.

Please select a Locality.

No matching category found.

No matching Locality found.

Q3.13:
Explain why cation are smaller and anions larger in radii than their parent atoms?

Solution :

Step 1: Definition of Atomic Radii and Electronic Configuration

The size of an atom or ion is determined by the electron cloud's boundary, which is influenced by the balance between the nuclear pull (effective nuclear charge, $Z_{eff}$) and the electron-electron repulsion. The radius of an atom is defined by its electronic configuration: $n s^x n p^y$.

Step 2: Analysis of Cation Formation (Positive Ions)

A cation is formed when an atom loses one or more electrons. This process affects the radius through two primary mechanisms:

  • Reduction in the Number of Shells: In many cases, the loss of an electron results in the complete removal of the outermost shell, causing a drastic decrease in ionic radius [Ref: Bohr’s Model].
  • Increased Effective Nuclear Charge ($Z_{eff}$): When electrons are removed, the number of protons remains constant, but the total electronic repulsion decreases. Consequently, the remaining electrons are pulled closer to the nucleus by the same positive nuclear charge. This increases the $Z_{eff}$ per electron, shrinking the electron cloud.

Mathematically, for a neutral atom $M$ with $Z$ protons and $e$ electrons, the formation of $M^+$ results in a higher ratio of $\frac{Z}{e}$, leading to orbital contraction.

Step 3: Analysis of Anion Formation (Negative Ions)

An anion is formed when an atom gains one or more electrons. This process increases the radius through the following mechanisms:

  • Increased Electron-Electron Repulsion: By adding an electron to the valence shell, the total inter-electronic repulsion increases significantly [Ref: Pauli Exclusion Principle and Hund’s Rule].
  • Decreased Effective Nuclear Charge ($Z_{eff}$): The number of protons remains constant, but the charge is now spread over a larger number of electrons. The reduced $Z_{eff}$ per electron means the nucleus cannot hold the valence shell as tightly, allowing the electron cloud to expand.

Step 4: Comparative Visualization of Ionic Radii

Parent Atom Cation (-e⁻) Anion (+e⁻)

Step 5: Summary Table of Ionic Trends

Ion Type Electron Count Nuclear Pull per Electron Size Relative to Parent
Cation Decreases Increases Smaller
Anion Increases Decreases Larger

Final Solution: Cations are smaller than their parent atoms because the loss of electrons increases the effective nuclear charge ($Z_{eff}$) exerted on the remaining electrons, causing them to be drawn closer to the nucleus. Conversely, anions are larger because the addition of electrons increases inter-electronic repulsion and decreases the $Z_{eff}$ per electron, causing the electron cloud to expand.


More Questions from Class 11 Chemistry Classification of Elements and Periodicity in Properties EXERCISES


CBSE Solutions for Class 11 Chemistry Classification of Elements and Periodicity in Properties


Chapters in CBSE - Class 11 Chemistry


Top Tutors who teach Classification of Elements and Periodicity in Properties

Manjunath  Class 11 Tuition trainer in Bangalore
(101)
superTutorSuper Tutor
locationImg Jayanagar East, Bangalore
experience 4 yrs of Exp students 47 students
greenClock 5902 hrs of classes completed
rsIcon 250 per hour
PhD Organic Chemistry at IIT Madras - One to One Tuition and Group Tuition
Online Classes Online Classes
regularClasses Tutor's home

I take classes for grade 11 of Karnataka State PUC, CBSE, ISC, NIOS and Cambridge or IGCSE AS Levels. I have 4 years of teaching experience.

Reena Roy

Attending this introductory chemistry demonstration session offered an insightful look into the program's academic standard. The instructor demonstrated excellent command of the subject matter, skillfully translating intricate chemical principles into accessible intellectual concepts.

Skills: Chemistry
Also teaches: CET Coaching, Class 10 Tuition and more

(19)
Top Tutor
locationImg Jayanagar 4th block, Bangalore
experience 11 yrs of Exp students 1 student
greenClock 296 hrs of classes completed
rsIcon 400 per hour
Home Science and Psychology teacher with 11 years of total teaching experience.
Online Classes Online Classes

- Helping the student gain confidence in themselves and with respect to the subject. - Thorough preparation with the help of model and previous year question papers. - Understanding the student's learning style and adapting my teaching style accordingly. - Making lessons interesting by using different methods of teaching (Sharing relevant YouTube links and weblinks).

Divya

I like the faculty and I feel I had the best environment for my studies . I learned the new things from my teachers who were very helpful in every way they could. You have been a great lecturer to me, and I fully enjoyed your lectures, you explained everything in detail about the media and early childhood education and way of storytelling etc, referring the notes given to us , it made it easier for me to understand. I'm beyond thankful to have you as one of my lecturer in my Masters. Thank you

Skills: Psychology , Home Science

Deepak Joshi Class 11 Tuition trainer in Bangalore
(50)
Top Tutor
locationImg Ashok Nagar D' Souza Layout, Bangalore
experience 13 yrs of Exp students 4 students
greenClock 1062 hrs of classes completed
rsIcon 700 per hour
Ph.D. Candidate | M.Sc. (Mathematics) | Former Faculty at BYJU'S (7 Years) & DPS Gurgaon (6 Years)
Online Classes Online Classes

13+ years of experience teaching Mathematics for grades 10 to 12. • Consistent record of 100% academic results. • Very friendly and supportive learning environment. • Encourages students to ask questions freely and confidently. • Strong focus on conceptual clarity and problem-solving skills. • Helps students build confidence and excel in Mathematics. • Fee structure for one-to-one classes: ₹800 per hour.

Aryan

He is a very good and experienced teacher who helps he improve at maths significantly. I used to get really bad marks earlier and then I started doing classes with him and I saw a significant improvement in my marks. He is one of the best maths teachers I have ever had.

Skills: Mathematics
Also teaches: Class 9 Tuition, Class 10 Tuition and more

(3)
Top Tutor
locationImg Sector 38, Chandigarh
experience 8 yrs of Exp students 1 student
greenClock 10 hrs of classes completed
Online Classes Online Classes

i am a teacher....I am giving home/online tuition since last 8years..I have a degree in masters of biotechnology...My key skills are best in competition as well as theoratical classes...I worked as biology project head in various institute as well as in various schools for preparing kids for NEET and for other medical entrance exams.

Skills: Biology

(1)
Top Tutor
locationImg Suddagunte Palya Balaji Nagar, Bangalore
experience Less than a yr Exp students 2 students
greenClock 27 hrs of classes completed
rsIcon 1000 per hour
Ph.D. Scholar, Researching on AI (Computer Science) and Exoplanetary Science (Physics).
Online Classes Online Classes

I am a Ph.D. Scholar. I completed my BCA from Calicut University, finished my MCA from Kristu Jayanti College (Autonomous), and currently pursuing my Ph.D. in Christ (Deemed to be University). Now, I am doing my research in Artificial Intelligence (Computer Science) and Exoplanetary Science (Physics). Therefore, I have relevant knowledge and experience in Computer Science and Physics concepts, including advanced topics like AI, ML, DL, NLP, Quantum Mechanics, Astrophysics, etc...

Skills: Physics , Computer Science
Also teaches: Class 12 Tuition, Class 10 Tuition and more

Other Subjects in CBSE - Class 11

Worksheet Icon

Download free CBSE - Class 11 Chemistry Classification of Elements and Periodicity in Properties EXERCISES worksheets

Download Now

Find Best Class 11 Tuition ?

Find Now »