Electron density and ionization temperatures were measured for inductively coupled argon plasma at atmospheric pressure. Different sample introduction systems were investigated. Samples containing Sn, Hg, Mg, and Fe and acidified with hydrochloric or acetic acids were introduced into plasma in the form of aerosol, gaseous mixture produced in the reaction of these solutions with NaBH₄ and the mixture of the aerosol and chemically generated gases. The electron densities measured from H_α, H_β, H_γ, and H_δ lines on the base of Stark broadening were compared. The study of the H Balmer series line profiles showed that the ne values from H_γ and H_δ were well consistent with those obtained from H_β which was considered as a common standard line for spectroscopic measurement of electron density. The ne values varied from 0.56·1015 to 1.32·1015 cm⁻³ and were the highest at loading mixture of chemically generated gases. The ionization temperatures of plasma, determined on the base of the Saha approach from ion-to-atom line intensity ratios, were lower for Sn and Hg (6500–7200 K) than those from Fe and Mg lines (7000–7800 K). The Sn II/Sn I and Hg II/Hg I, Fe II/Fe I, and Mg II/Mg I intensity ratios and the electron densities (ne) were dependent on experimental conditions of plasma generation. Experimental and theoretically calculated ionization degrees were compared.