Atomic orbitals
Why can't two electrons in the same orbital spin in the same direction?
Because of the Pauli Exclusion Principle, which states that no two electrons in an atom can have the same set of quantum numbers. In the same orbital, electrons must have opposite spins to be distinguishable.
Why is sodium (Na) so reactive but neon (Ne) isn't?
Sodium has 1 electron in its outer shell (3s¹), which it easily loses to become stable (Na⁺). Neon already has a full outer shell (2s² 2p⁶), making it very stable and unreactive — a noble gas.
Why does salt (NaCl) dissolve in water so easily, while rust (Fe₂O₃) doesn’t?
Salt is an ionic compound, and water (a polar solvent) pulls apart the Na⁺ and Cl⁻ ions easily. Rust has strong ionic and covalent bonds in a complex crystal structure, which water can’t break apart easily.
… the way in which teachers and students communicate in the classroom, outside the classroom and in email correspondence.
How do you understand teacher-student interaction?
Why does calcium end up in our bones instead of potassium, even though both are metals?
Calcium (Ca²⁺) forms strong ionic bonds with phosphate in bones (Ca₃(PO₄)₂), creating hard, solid structures. Potassium (K⁺), although also a metal, stays dissolved in body fluids and plays a role in nerve signals instead.
Why can we bend metals like copper into wires, but not crystals like quartz?
Metals have metallic bonds — a “sea of electrons” allows layers of atoms to slide over each other. Quartz (SiO₂) has a rigid covalent network structure that breaks if disturbed — making it brittle.
Why are fireworks different colors?
Different metal atoms (like copper, strontium, sodium) have electrons that jump to higher orbitals when heated. When they fall back to their original orbitals, they release light of specific colors depending on the energy gap between orbitals.
Copper → blue/green flame
Strontium → red flame
Sodium → yellow flame
If you heat a metal wire in a flame and it glows, what does this tell you about its electrons?
The heat excites electrons to higher orbitals. When they fall back down to lower energy levels, they release visible light, causing the glow. This is how flame tests work!
Why does water (a covalently bonded molecule) have a much higher boiling point than similar-sized molecules like methane?
Water molecules form hydrogen bonds — strong intermolecular forces — that require more energy (heat) to break. Methane has weak dispersion forces, so it boils at a much lower temperature.
My ends are charged, I love to stick,
To ions or poles, I bond quite quick.
I hold salt crystals tight and strong,
But in water, I won’t last long.
What kind of bonding could this be,
Between a metal and non-metal like me?
Ionic bonding
Why do we put lemon juice on cut apples to stop them from browning?
Lemon juice contains ascorbic acid (Vitamin C), which acts as an antioxidant. It prevents the oxidation reaction (which causes browning) from happening.
Why do we use aluminum foil to wrap food, but not something like sodium metal?
Aluminum forms a protective oxide layer and is stable due to strong metallic bonds. Sodium is highly reactive and would react with air or moisture — not safe for food!
I orbit round, but not like stars,
I jump in shells, not very far.
I’m tiny, negative, full of flair —
You’ll never find me staying there!
What am I, light and small,
Yet key to atoms one and all?
Electron
I float like clouds in every sip,
Not fully mixed, I take a trip.
Suspended high, I stay between—
Who am I?
Suspension / Colloid
Compare the bonding nature and structure of diamond and silicon dioxide (quartz). Why does quartz melt more easily than diamond, even though both are covalent networks?
Diamond has each carbon atom bonded tetrahedrally to 4 others, forming a very rigid and strong 3D structure.
Quartz (SiO₂) consists of a tetrahedral framework where each Si is bonded to 4 O atoms, and each O bridges two Si atoms.