Class 2. Calcium, barium, strontium.
Class 3. Aluminium, cerium, didymium, erbium, glucinium, lanthanum, thorium, yttrium, zirconium.
Class 4. Zinc class: cadmium, magnesium, zinc.
Class 5. Iron class: cobalt, chromium, indium, iron, manganese, nickel, uranium.
Class 6. Tin class: niobium, tantalum, tin, titanium.
Class 7. Tungsten class: molybdenum, tungsten, vanadium.
Class 8. Arsenic class: antimony, arsenic, bismuth.
Class 9. Lead class: lead, thallium.
Class 10. Silver class: copper, mercury, silver.
Class 11. Gold class: gold, iridium, osmium, palladium, platinum, rhodium, ruthenium.