Atomic Structure & Periodic Trends
What subatomic particle determines an element’s identity?
What is Protons?
Explanation: The atomic number equals the number of protons, which defines the element.
What type of bond involves unequal sharing of electrons?
what is Polar covalent bond?
What thermodynamic quantity measures disorder?
What is Entropy (ΔS)?
What is the pH of a neutral solution at 25°C?
What is 7?
What unit measures solution concentration?
What is Molarity (M)?
Which periodic trend generally increases from left to right across a period?
What is Electronegativity?
Explanation: Nuclear charge increases, pulling electrons closer.
What VSEPR shape results from 4 bonding pairs and 0 lone pairs?
What is Tetrahedral?
A reaction is spontaneous when ΔG is:
What is Negative?
What makes a strong acid “strong”?
What is Complete dissociation in water?
What happens to boiling point when solute is added?
What is It increases?
Why do atomic radii decrease across a period?
What is Increased effective nuclear charge?
Explanation: More protons pull electrons inward without much added shielding.
Why does NH₃ have a smaller bond angle than CH₄?
What is Lone pair repulsion?
Explanation: Lone pairs repel more strongly than bonding pairs.
How does a catalyst affect activation energy?
What is Lowers it?
Explanation: Catalysts provide an alternate pathway.
Which acid is stronger: HCl or HF?
What is HCl?
Explanation: HF has strong H–F bonds that resist dissociation.
Why does salt lower the freezing point of water?
What is Disrupts crystal formation?
Explanation: Colligative properties depend on particle number.
Which element has the highest first ionization energy?
What is Helium?
Explanation: Small size + full valence shell = very hard to remove an electron.
Which intermolecular force is strongest: London dispersion, dipole–dipole, or hydrogen bonding?
What is Hydrogen bonding?
Why are exothermic reactions often spontaneous at low temperatures?
What is ΔH is negative and dominates ΔG?
Explanation: ΔG = ΔH − TΔS
What happens to equilibrium when more reactant is added?
What is Shifts toward products?
Explanation: Le Châtelier’s principle.
In a galvanic cell, electrons flow from:
What is Anode to cathode?
Why does oxygen have a lower first ionization energy than nitrogen?
What is Electron–electron repulsion in paired orbitals?
Explanation: Oxygen has paired electrons in a p-orbital, making removal easier.
Why does HF have a higher boiling point than HCl?
What is Hydrogen bonding?
Explanation: Fluorine’s high electronegativity allows strong H-bonding.
A reaction has ΔH > 0 and ΔS > 0. When is it spontaneous?
What is At high temperatures?
Explanation: Large TΔS makes ΔG negative.
Why does a buffer resist changes in pH?
What is Presence of weak acid/base conjugate pair?
Explanation: They neutralize added H⁺ or OH⁻.
Which electrode undergoes oxidation?
What is Anode?
Explanation: AN OX, RED CAT (Anode = Oxidation, Cathode = Reduction)