Nuclei and Radioactivity
NIOS · Class 12 · Physics
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See them allState the composition of an atomic nucleus. What are nucleons?
Answer
An atomic nucleus contains two types of particles: 1. Protons – positively charged particles 2. Neutrons – neutral (no charge) particles Protons and neutrons together are called NUCLEONS. Key values…
Define: (a) Atomic Number (Z), (b) Mass Number (A), (c) Neutron Number (N). Write their relationship.
Answer
Definitions: (a) Atomic Number (Z) = Number of protons in the nucleus = Number of electrons in a neutral atom (b) Mass Number (A) = Total number of nucleons (protons + neutrons) A = Z + N (c) …
Differentiate between Isotopes, Isobars, and Isotones with one example each.
Answer
ISOTOPES – Same Z, Different A (same element, different neutrons) • Example: ¹²₆C and ¹⁴₆C (both are carbon, Z=6) • Same chemical properties, different physical properties ISOBARS – Same A, Different…
From these nuclei, identify the Isotopes, Isobars, and Isotones: ³⁵₁₇Cl, ³⁷₁₇Cl, ⁴⁰₁₈Ar, ⁴⁰₂₀Ca, ²³₁₁Na, ²⁴₁₂Mg
Answer
Step 1 – Check for same Z (Isotopes): • ³⁵₁₇Cl and ³⁷₁₇Cl → both have Z=17 → ISOTOPES ✓ Step 2 – Check for same A (Isobars): • ⁴⁰₁₈Ar and ⁴⁰₂₀Ca → both have A=40 → ISOBARS ✓ Step 3 – Check for same …
Write the formula for nuclear radius. Calculate the radius of the nucleus of ²⁷₁₃Al. (r₀ = 1.2 × 10⁻¹⁵ m)
Answer
Formula: R = r₀ × A^(1/3) where: • r₀ = 1.2 fm = 1.2 × 10⁻¹⁵ m (unit nuclear radius) • A = mass number • 1 fermi (fm) = 10⁻¹⁵ m For ²⁷₁₃Al: A = 27 Step 1: A^(1/3) = 27^(1/3) = 3 Step 2: R = 1.2 × 1…
Calculate the approximate density of nuclear matter using the hydrogen nucleus. (Mass of H = 1.673 × 10⁻²⁷ kg, R = 1.2 × 10⁻¹⁵ m)
Answer
Given: • M_H = 1.673 × 10⁻²⁷ kg • R_H = 1.2 × 10⁻¹⁵ m (since A=1 for hydrogen) Formula: density d = M / (4/3 × π × R³) Step 1: R³ = (1.2 × 10⁻¹⁵)³ = 1.728 × 10⁻⁴⁵ m³ Step 2: Volume = (4/3) × π × 1.
What is the Unified Atomic Mass Unit (u)? Express 1 u in kg and MeV.
Answer
Definition: 1 u (unified atomic mass unit) is defined as 1/12th of the mass of one ¹²₆C atom. 1 u = (1/12) × mass of ¹²C atom = (1/12) × 1.99267 × 10⁻²⁶ kg = 1.660565 × 10⁻²⁷ kg ≈ 1.66 × …
Define Mass Defect (Δm). Write its formula for a nucleus ᴬ_Z X.
Answer
Definition: The mass of a nucleus is ALWAYS less than the sum of the masses of its individual nucleons (protons + neutrons). This difference in mass is called the MASS DEFECT (Δm). Formula: Δm = [Z·m…
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