Rutherford's gold-foil experiment Tamil revision mind map built around a labelled apparatus diagram: an alpha source firing a narrow beam at thin gold foil surrounded by a zinc-sulphide scintillation screen, the three observations that most alpha particles passed straight through undeflected, a small fraction deflected at large angles including about one in eight thousand beyond ninety degrees, and about one in twenty thousand bounced straight back, contradicting Thomson's plum-pudding model and leading Rutherford to conclude the atom is mostly empty space with a tiny dense positively charged nucleus.