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NCERT Textbook: Structure of Atom
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FAQs on NCERT Textbook: Structure of Atom
| 1. What exactly are electrons, protons, and neutrons in an atom? |  |
Ans. Electrons are negatively charged particles orbiting the nucleus, protons are positively charged particles inside the nucleus, and neutrons are neutral particles also in the nucleus. Together, protons and neutrons form the atomic nucleus and determine an atom's mass number, while electrons determine its chemical properties and bonding behaviour.
| 2. How do Bohr's model and the modern quantum mechanical model differ in explaining atomic structure? | |
Ans. Bohr's model describes electrons moving in fixed circular orbits around the nucleus with definite energy levels, while the quantum mechanical model uses probability distributions called orbitals to show where electrons are likely found. The quantum model is more accurate for predicting atomic behaviour and doesn't assume fixed electron paths like Bohr's model does.
| 3. Why do atoms have different atomic numbers and mass numbers if they're made of the same particles? | |
Ans. Atomic number equals the number of protons, which varies between elements and defines the element itself. Mass number is the total of protons and neutrons combined. Different elements have different proton counts, and even the same element can have different neutron counts, creating isotopes with identical chemical properties but different masses.
| 4. What's the difference between energy levels, subshells, and orbitals in atomic structure? | |
Ans. Energy levels (or shells) are the main orbits where electrons reside; subshells (s, p, d, f) within each level have different shapes and energies; orbitals are three-dimensional regions where electrons are 99% likely to be found. Each orbital can hold maximum two electrons, and understanding this hierarchy is crucial for predicting electron configuration and chemical reactivity.
| 5. How does the aufbau principle help determine where electrons go in an atom? | |
Ans. The aufbau principle states electrons fill orbitals in order of increasing energy, starting from the lowest. This means the 1s orbital fills before 2s, which fills before 2p, and so on. Using this rule alongside Hund's rule and the Pauli exclusion principle allows students to write accurate electron configurations for any element and predict its valence electrons.
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