Periodic trends in atomic properties
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Flip to reveal answersWhat two factors explain almost every periodic trend?
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All 12 Flashcards — Periodic trends in atomic properties
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Question
What two factors explain almost every periodic trend?
Answer
**Nuclear charge** (proton pull) and **shielding/distance** (inner shells + extra shells).
Question
Define first ionisation energy.
Answer
The energy needed to remove one mole of electrons from one mole of **gaseous** atoms: X(g) → X⁺(g) + e⁻.
Question
Define atomic radius.
Answer
**Half** the distance between the nuclei of two bonded atoms — a measure of atom size.
Question
Define electronegativity.
Answer
How strongly an atom attracts a **bonding pair** of electrons (Pauling scale).
Question
Define electron affinity.
Answer
The energy change when one mole of gaseous atoms **gains** an electron: X(g) + e⁻ → X⁻(g).
Question
Atomic radius trend across a period?
Answer
**Decreases** — greater nuclear charge with similar shielding pulls the outer shell in.
Question
Atomic radius trend down a group?
Answer
**Increases** — each element has an extra electron shell.
Question
First ionisation energy across a period and down a group?
Answer
**Increases** across a period (stronger pull); **decreases** down a group (further out, more shielded).
Question
Electronegativity trend?
Answer
**Increases** across a period, **decreases** down a group (fluorine is the most electronegative).
Question
How does a cation's radius compare with its atom?
Answer
A cation is **smaller** than its atom (it often loses a whole shell).
Question
How does an anion's radius compare with its atom?
Answer
An anion is **larger** than its atom (extra electron–electron repulsion spreads the shell out).
Question
Key marking phrase for a trend explanation?
Answer
Compare **nuclear charge**, compare **shielding/distance**, then state the **net effect** (held more/less tightly).
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Topic 3.1 hub
The periodic table: classification of elements
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