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What are Isotopes?
Grade Level:
Class 12
AI/ML, Physics, Biotechnology, FinTech, EVs, Space Technology, Climate Science, Blockchain, Medicine, Engineering, Law, Economics
Definition
What is it?
Isotopes are different forms of the same chemical element. They have the same number of protons in their nucleus but a different number of neutrons, which means they have the same atomic number but different mass numbers.
Simple Example
Quick Example
Imagine you have two friends, Rahul and Rohan. Both are in Class 10 (same atomic number, representing the element). Rahul weighs 50 kg, but Rohan weighs 52 kg (different mass numbers, due to different numbers of neutrons). They are like isotopes of each other – same class, different weights.
Worked Example
Step-by-Step
Let's look at Carbon (C) isotopes.
1. **Carbon-12 (C-12):** This is the most common form of carbon. Its atomic number is 6, meaning it has 6 protons.
2. To find the number of neutrons, we subtract the atomic number from the mass number. For C-12, mass number is 12.
3. Neutrons = Mass Number - Protons = 12 - 6 = 6 neutrons.
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4. **Carbon-14 (C-14):** This is another isotope of carbon. Its atomic number is also 6 (because it's carbon), so it has 6 protons.
5. Its mass number is 14.
6. Neutrons = Mass Number - Protons = 14 - 6 = 8 neutrons.
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Answer: C-12 has 6 protons and 6 neutrons. C-14 has 6 protons and 8 neutrons. Both are carbon, but C-14 is heavier due to more neutrons.
Why It Matters
Understanding isotopes is crucial in many fields. In medicine, radioactive isotopes are used for imaging like PET scans to diagnose diseases or in radiation therapy to treat cancer. In climate science, studying isotopes in ice cores helps scientists understand past climates, and in forensics, carbon dating helps determine the age of ancient artifacts.
Common Mistakes
MISTAKE: Thinking isotopes are different elements. | CORRECTION: Isotopes are always the SAME element, meaning they have the same number of protons. Only the number of neutrons differs.
MISTAKE: Confusing atomic number and mass number. | CORRECTION: Atomic number is the number of protons (defines the element). Mass number is protons + neutrons (determines the isotope's weight).
MISTAKE: Assuming isotopes have different chemical properties. | CORRECTION: Because isotopes have the same number of protons and electrons (in a neutral atom), their chemical properties are almost identical. Their physical properties (like density) can differ due to mass difference.
Practice Questions
Try It Yourself
QUESTION: An atom has 17 protons and 18 neutrons. What is its mass number? | ANSWER: Mass number = Protons + Neutrons = 17 + 18 = 35
QUESTION: Chlorine has two main isotopes: Chlorine-35 and Chlorine-37. How many neutrons does each isotope have if the atomic number of Chlorine is 17? | ANSWER: Chlorine-35: Neutrons = 35 - 17 = 18. Chlorine-37: Neutrons = 37 - 17 = 20.
QUESTION: An element 'X' has an atomic number of 8. It has two isotopes, X-16 and X-18. How many protons and neutrons are in each isotope? | ANSWER: For X-16: Protons = 8, Neutrons = 16 - 8 = 8. For X-18: Protons = 8, Neutrons = 18 - 8 = 10.
MCQ
Quick Quiz
Which of the following statements is TRUE about isotopes?
They have different atomic numbers.
They have the same number of protons but different number of neutrons.
They are different elements.
They have the same mass number.
The Correct Answer Is:
B
Isotopes are atoms of the same element, meaning they have the same number of protons (and thus same atomic number). Their difference lies in the number of neutrons, leading to different mass numbers.
Real World Connection
In the Real World
In India, isotopes are used in various fields. For example, radioactive isotopes like Cobalt-60 are used in hospitals across India for cancer treatment. The Bhabha Atomic Research Centre (BARC) in Mumbai produces and supplies these isotopes for medical and industrial applications, helping save lives and advance technology.
Key Vocabulary
Key Terms
PROTONS: Positively charged particles in the nucleus | NEUTRONS: Neutral particles in the nucleus | ATOMIC NUMBER: Number of protons in an atom's nucleus | MASS NUMBER: Total number of protons and neutrons in an atom's nucleus | RADIOACTIVE ISOTOPES: Unstable isotopes that decay and emit radiation
What's Next
What to Learn Next
Now that you understand isotopes, you're ready to explore radioactivity and nuclear reactions. This will help you understand how some isotopes are used to generate electricity in nuclear power plants or how they help doctors see inside our bodies.
