Writing a nucleus: ᴬ_Z Xनाभिक लिखने का तरीका: ᴬ_Z XWriting a nucleus: ᴬ_Z X

NCERT Section 13.2 · Class 12 Physics · Chapter 13 · interactive diagram

Parts and what they mean

• Mass number A (द्रव्यमान संख्या A) — Total number of nucleons (protons + neutrons). Written at the top left.
• Atomic number Z (परमाणु क्रमांक Z) — Number of protons = number of electrons in the neutral atom. Nuclear charge = +Ze. Written at the bottom left.
• Chemical symbol X (रासायनिक प्रतीक X) — Au = gold. The symbol already fixes Z, but Z is written for convenience.
• Neutron number N (न्यूट्रॉन संख्या N) — N = A − Z. Gold-197 has 118 neutrons.
• Nucleus (नाभिक) — Protons and neutrons (together called nucleons) packed in a tiny sphere. Electrons are all outside the nucleus.
• Proton (प्रोटॉन) — Charge +e, mass 1.00727 u = 1.67262 × 10⁻²⁷ kg. Stable.
• Neutron (न्यूट्रॉन) — No charge, mass 1.00866 u = 1.6749 × 10⁻²⁷ kg. A free neutron decays (mean life about 1000 s); inside a nucleus it is stable.

Original diagram drawn by Simple Learning Hub, based on NCERT Section 13.2. Report a mistake