NIOS Class 12 Chemistry — Flashcards

A: The three fundamental particles are: 1. Electron (e⁻) - Negative charge (-1) 2. Proton (p⁺) - Positive charge (+1) 3. Neutron (n⁰) - Neutral charge (0) Electrons are approximately 1/1840th the mass o

A: Atomic Number (Z) = Number of protons in the nucleus = Number of electrons in a neutral atom Mass Number (A) = Total number of protons + neutrons Number of Neutrons = A - Z Example: Oxygen-17 has Z

A: For ₈O¹⁷: Step 1: Identify atomic number (Z) = 8 - Number of protons = 8 - Number of electrons = 8 (in neutral atom) Step 2: Identify mass number (A) = 17 Step 3: Calculate neutrons - Number of neu

A: Dobereiner's Law of Triads (1817) states that when three closely related elements are grouped together, the atomic weight of the middle element is approximately the arithmetical mean of the other two.

A: Newlands' Law of Octaves (1863): When elements are arranged in order of increasing atomic weight, every eighth element has similar properties, like musical notes repeating in octaves. WHY IT FAILED: T

A: Mendeleev's greatest contribution (1869) was: (1) Arranging elements by INCREASING ATOMIC WEIGHT and demonstrating periodic recurrence of properties. (2) LEAVING GAPS for undiscovered elements (Sc, Ga

A: Valence electrons are electrons in the outermost shell (valence shell) of an atom. They are crucial because: (1) They determine the combining capacity or valency of an atom, (2) They participate direc

A: A chemical bond is an attractive force that holds atoms together in a molecule. Definition: When two atoms approach each other, the energy of the combined system becomes less than the sum of energies

A: Kossel's Theory: Atoms achieve stable noble gas configuration by losing or gaining electrons. For NaCl formation: Na (2,8,1) loses 1 electron → Na⁺ (2,8 - like Ne). Cl (2,8,7) gains 1 electron → Cl⁻ (