π¬ STRUCTURE OF THE ATOM (MCQs Notes)
πΉ 1. Basic Definition
- Atom = Smallest unit of an element that retains its properties
- Atom is electrically neutral β protons = electrons
πΉ 2. Subatomic Particles (VERY IMPORTANT)
| Particle | Charge | Mass | Location |
|---|---|---|---|
| Proton | +1 | 1 amu | Nucleus |
| Neutron | 0 | 1 amu | Nucleus |
| Electron | β1 | ~0 | Shells |
π MCQ traps:
- Proton determines element identity
- Electron determines chemical behavior
- Neutron affects mass only
πΉ 3. Atomic Number & Mass Number
- Atomic number (Z) = Number of protons
- Mass number (A) = Protons + Neutrons
π Formula:
- Neutrons = A β Z
π MCQ:
- Change in proton β new element
πΉ 4. Isotopes, Isobars, Ions
Isotopes
- Same element, different neutrons
- Example: C-12, C-14
π Used in radioactivity & medicine
Isobars
- Same mass number, different elements
Ions
- Loss/gain of electrons
- Cation (+), Anion (β)
Energy and its Procurement: Structure of the Atom and Radioactivity
πΉ 5. Atomic Models (VERY IMPORTANT MCQs)
Dalton Model
- Atom indivisible (β wrong now)
Thomson Model
- βPlum pudding modelβ
- Electron embedded in positive sphere
Rutherford Model
- Nucleus discovered
- Atom mostly empty space
- Gold foil experiment
π MCQ:
- Foil used β Gold
Bohr Model
- Electrons move in fixed energy levels (shells)
πΉ 6. Electron Shells & Configuration
- Shells: K, L, M, N
- Max electrons = 2nΒ²
π Examples:
- K = 2
- L = 8
- M = 18
π Stability:
- Outer shell = 8 electrons (octet rule)
πΉ 7. Important Discoveries
| Scientist | Discovery |
|---|---|
| J.J. Thomson | Electron |
| Rutherford | Nucleus |
| Chadwick | Neutron |
π MCQ:
- Neutron discovered by Chadwick
β’οΈ RADIOACTIVITY (MCQs Notes)
πΉ 8. Definition
- Radioactivity = Spontaneous emission of radiation from unstable nucleus
πΉ 9. Types of Radiation (VERY IMPORTANT)
| Radiation | Charge | Penetration | Nature |
|---|---|---|---|
| Alpha (Ξ±) | +2 | Low | Helium nucleus |
| Beta (Ξ²) | β1 | Medium | Electron |
| Gamma (Ξ³) | 0 | High | Electromagnetic wave |
π MCQ traps:
- Most penetrating β Gamma
- Most ionizing β Alpha
πΉ 10. Radioactive Decay
- Unstable nucleus β emits radiation β becomes stable
π Types:
- Alpha decay
- Beta decay
- Gamma emission
πΉ 11. Half-Life (VERY IMPORTANT)
- Time for half of substance to decay
π Key points:
- Constant for each element
- Independent of temperature & pressure
πΉ 12. Nuclear Reactions
Fission
- Splitting of heavy nucleus (Uranium)
- Used in nuclear reactors
Fusion
- Combining light nuclei
- Occurs in Sun
π MCQ:
- Sun energy β Fusion
πΉ 13. Uses of Radioactivity
- Medicine (cancer treatment)
- Carbon dating
- Power generation
- Industry
πΉ 14. Hazards of Radiation
- Cancer
- Genetic mutations
- Tissue damage
π₯ MOST REPEATED MCQ POINTS
- Atom neutral β protons = electrons
- Nucleus contains β protons + neutrons
- Electron mass negligible
- Gold foil β Rutherford
- Neutron β Chadwick
- Atomic number = protons
- Isotopes β same element
- Gamma rays β highest penetration
- Alpha β highest ionization
- Half-life β constant
π― SUPER QUICK REVISION (1-Minute)
- Atom = proton + neutron (nucleus) + electron
- Proton β identity
- Neutron β mass
- Electron β reactions
- Isotopes β same Z, different A
- Alpha (+), Beta (β), Gamma (0)
- Gamma β most penetrating
- Half-life β fixed
- Fusion β Sun
- Fission β nuclear reactors
π¬ STRUCTURE OF ATOM MCQs (1β50)
πΉ Basic & Subatomic Particles
- Who discovered the electron?
A) Rutherford
B) Chadwick
C) J.J. Thomson β
D) Bohr - Proton has charge:
A) β1
B) 0
C) +1 β
D) +2 - Neutron has charge:
A) +1
B) β1
C) 0 β
D) +2 - Electron is located in:
A) Nucleus
B) Orbit/shell β
C) Proton
D) Core - Mass of electron is:
A) Equal to proton
B) Negligible β
C) Double
D) Zero - Nucleus contains:
A) Electrons
B) Protons & neutrons β
C) Only neutrons
D) Only protons - Atomic number represents:
A) Neutrons
B) Electrons
C) Protons β
D) Ions - Mass number equals:
A) p + e
B) p + n β
C) n + e
D) e only - Number of neutrons =
A) Z β A
B) A β Z β
C) A + Z
D) ZΒ² - Atom is neutral because:
A) No charge
B) p = e β
C) n = p
D) e = n
πΉ Atomic Models
- Dalton model states atom is:
A) Divisible
B) Indivisible β
C) Charged
D) Hollow - Thomson model is called:
A) Nuclear
B) Solar
C) Plum pudding β
D) Quantum - Rutherford experiment used:
A) Silver foil
B) Gold foil β
C) Copper foil
D) Iron foil - Rutherford discovered:
A) Electron
B) Neutron
C) Nucleus β
D) Proton - Most of atom is:
A) Solid
B) Empty space β
C) Liquid
D) Gas - Bohr model explains:
A) Nucleus
B) Fixed energy levels β
C) Electrons at rest
D) Proton motion - Electrons revolve in:
A) Random paths
B) Fixed orbits β
C) Nucleus
D) Core - Energy levels are:
A) Continuous
B) Quantized β
C) Infinite
D) Random
πΉ Isotopes, Ions
- Isotopes have:
A) Same mass
B) Same protons β
C) Same neutrons
D) Same ions - Isobars have:
A) Same atomic number
B) Same mass number β
C) Same element
D) Same electrons - Ion is formed by:
A) Proton change
B) Electron gain/loss β
C) Neutron change
D) Mass change - Cation is:
A) Negative
B) Positive β
C) Neutral
D) Gas - Anion is:
A) Positive
B) Negative β
C) Neutral
D) Solid - Changing protons gives:
A) Isotope
B) New element β
C) Ion
D) Compound
πΉ Electron Configuration
- Max electrons in shell =
A) nΒ²
B) 2nΒ² β
C) nΒ³
D) 2n - K shell holds:
A) 8
B) 2 β
C) 18
D) 32 - L shell holds:
A) 2
B) 8 β
C) 18
D) 32 - Octet rule means:
A) 2 electrons
B) 8 electrons β
C) 18 electrons
D) 32 electrons - Valence electrons are:
A) Inner shell
B) Outer shell β
C) Nucleus
D) Core - Chemical properties depend on:
A) Neutrons
B) Protons
C) Electrons β
D) Mass
πΉ Scientists
- Neutron discovered by:
A) Thomson
B) Rutherford
C) Chadwick β
D) Bohr - Proton discovered by:
A) Rutherford β
B) Chadwick
C) Thomson
D) Dalton - Bohr introduced:
A) Nucleus
B) Energy levels β
C) Electron
D) Neutron - Thomson used:
A) Alpha rays
B) Cathode rays β
C) Gamma rays
D) Beta rays
πΉ Miscellaneous
- Atomic mass unit (amu) measures:
A) Charge
B) Mass β
C) Volume
D) Density - 1 amu equals:
A) Proton mass approx β
B) Electron mass
C) Neutron charge
D) Ion - Relative atomic mass depends on:
A) Isotopes β
B) Ions
C) Shells
D) Charge - Period number shows:
A) Protons
B) Shells β
C) Neutrons
D) Charge - Group number shows:
A) Neutrons
B) Valence electrons β
C) Shells
D) Mass - Atom size mostly due to:
A) Nucleus
B) Electron cloud β
C) Proton
D) Neutron
β’οΈ RADIOACTIVITY MCQs (51β100)
πΉ Basic Concepts
- Radioactivity is:
A) Artificial
B) Spontaneous emission β
C) Controlled reaction
D) Heat - Radioactivity occurs in:
A) Stable atoms
B) Unstable nuclei β
C) Electrons
D) Molecules - Discovered by:
A) Rutherford
B) Becquerel β
C) Thomson
D) Bohr
πΉ Types of Radiation
- Alpha particle charge:
A) β1
B) +1
C) +2 β
D) 0 - Beta particle is:
A) Proton
B) Electron β
C) Neutron
D) Photon - Gamma rays are:
A) Particles
B) Waves β
C) Ions
D) Neutrons - Most penetrating:
A) Alpha
B) Beta
C) Gamma β
D) Proton - Least penetrating:
A) Alpha β
B) Beta
C) Gamma
D) Neutron - Most ionizing:
A) Gamma
B) Beta
C) Alpha β
D) Proton
πΉ Nuclear Reactions
- Fission is:
A) Joining
B) Splitting nucleus β
C) Heating
D) Cooling - Fusion is:
A) Splitting
B) Joining nuclei β
C) Ionization
D) Radiation - Sun produces energy by:
A) Fission
B) Fusion β
C) Combustion
D) Decay - Nuclear reactor uses:
A) Fusion
B) Fission β
C) Combustion
D) Evaporation
πΉ Half-Life
- Half-life is:
A) Total decay
B) Half decay time β
C) Full decay
D) Reaction time - Half-life depends on:
A) Temperature
B) Pressure
C) Nature of element β
D) Volume - Half-life is:
A) Variable
B) Constant β
C) Increasing
D) Decreasing
πΉ Effects & Uses
- Radiation causes:
A) Cooling
B) Mutation β
C) Growth
D) Expansion - Used in cancer treatment:
A) Alpha
B) Beta
C) Gamma β
D) Proton - Carbon dating uses:
A) C-12
B) C-14 β
C) O-16
D) H-1 - Nuclear energy advantage:
A) Low output
B) High output β
C) No waste
D) No risk
πΉ Decay Changes
- Alpha decay reduces mass by:
A) 1
B) 2
C) 4 β
D) 8 - Beta decay changes:
A) Mass
B) Atomic number β
C) Charge
D) Volume - Gamma decay changes:
A) Mass
B) Charge
C) Energy only β
D) Size
πΉ Miscellaneous
- Uranium is:
A) Stable
B) Radioactive β
C) Gas
D) Liquid - Radioactive waste is:
A) Safe
B) Dangerous β
C) Useful
D) Edible - Nuclear force is:
A) Weak
B) Strong β
C) Magnetic
D) Electric - Radiation unit:
A) Joule
B) Sievert β
C) Watt
D) Volt - Gamma rays are:
A) Charged
B) Neutral β
C) Positive
D) Negative - Alpha particle is:
A) Helium nucleus β
B) Electron
C) Photon
D) Proton - Beta rays deflected by:
A) Electric field β
B) Gravity
C) Heat
D) Sound
πΉ Final Quick MCQs
- Most dangerous radiation:
A) Alpha
B) Gamma β
C) Beta
D) Proton - Shielding for gamma:
A) Paper
B) Lead β
C) Wood
D) Plastic - Shielding for alpha:
A) Paper β
B) Lead
C) Steel
D) Glass - Stability depends on:
A) Neutron-proton ratio β
B) Electrons
C) Charge
D) Mass - Radioactive decay is:
A) Artificial
B) Natural β
C) Forced
D) Chemical - Radiation detected by:
A) Thermometer
B) Geiger counter β
C) Barometer
D) Voltmeter - Beta decay emits:
A) Proton
B) Electron β
C) Neutron
D) Photon - Fusion requires:
A) Low temp
B) High temp β
C) Pressure only
D) Water - Fission produces:
A) Small energy
B) Large energy β
C) No energy
D) Heat only - Nuclear energy source:
A) Coal
B) Uranium β
C) Gas
D) Oil - Radioactivity leads to:
A) Stability
B) Decay to stable nucleus β
C) Growth
D) Reaction - Isotopes used in:
A) Medicine β
B) Cooking
C) Painting
D) Farming - Alpha particles stopped by:
A) Air few cm β
B) Lead
C) Steel
D) Glass - Gamma rays travel at:
A) Sound speed
B) Light speed β
C) Slow
D) Variable - Nuclear energy is:
A) Chemical
B) Atomic nucleus energy β
C) Heat
D) Light - Beta particles have:
A) Positive charge
B) Negative charge β
C) Neutral
D) Double charge - Radioactivity discovered in:
A) 1896 β
B) 1900
C) 1910
D) 1920 - Alpha particles are:
A) Heavy β
B) Light
C) Neutral
D) Waves - Nuclear reactions involve:
A) Electrons
B) Nucleus β
C) Molecules
D) Ions - Final aim of decay:
A) Instability
B) Stability β
C) Growth
D) Energy loss
π― Exam Tip
Focus heavily on:
- Scientists & discoveries
- Alpha, beta, gamma differences
- Atomic number & mass number
- Decay rules (alpha β4 mass, β2 Z)