Explanation:
Rusting is a chemical change because iron reacts with oxygen and moisture to form a completely new chemical substance, hydrated iron(III) oxide (Fe₂O₃·xH₂O), which has different chemical properties from iron and cannot be easily reversed by simple physical means like heating or cooling.
Explanation:
Aluminium displaces iron from iron(III) oxide because Al is more reactive. This is a single displacement (or thermite) reaction. Also redox: Al oxidized, Fe reduced. Combination: one product; decomposition: one reactant.
Explanation:
Atomic radius decreases across a period due to increasing nuclear charge. Sodium (Na) is the first element in period 3, thus it has the largest atomic radius. Argon (noble gas) has the smallest (though noble gas radii are van der Waals and larger than covalent, but still trend is decreasing). For metals, Na > Mg > Al; non-metals further smaller.
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