Metals extracted by electrometallurgy:
Electrometallurgy is a process in which metals are extracted from their ores using electrical energy. In this process, the metal ions present in the ore are reduced to the elemental form at the cathode by the passage of electric current. The metals that can be extracted by electrometallurgy include:

- Copper (Cu): Copper is commonly extracted from its ore, copper pyrite (CuFeS2), using the process of electrometallurgy. The copper ions present in the ore are reduced to copper metal at the cathode.

- Aluminum (Al): Aluminum is extracted from its ore, bauxite (Al2O3.2H2O), using the electrometallurgical process of electrolysis. The aluminum ions present in the ore are reduced to aluminum metal at the cathode.

- Sodium (Na): Sodium is extracted from its ore, sodium chloride (NaCl), using the process of electrolysis. The sodium ions present in the ore are reduced to sodium metal at the cathode.

- Potassium (K): Potassium is also extracted from its ore, potassium chloride (KCl), using the process of electrolysis. The potassium ions present in the ore are reduced to potassium metal at the cathode.

- Magnesium (Mg): Magnesium is extracted from its ore, magnesium chloride (MgCl2), using the process of electrolysis. The magnesium ions present in the ore are reduced to magnesium metal at the cathode.

- Zinc (Zn): Zinc is extracted from its ore, zinc sulfide (ZnS), using the process of electrometallurgy. The zinc ions present in the ore are reduced to zinc metal at the cathode.

Therefore, the number of metals extracted by electrometallurgy among Ca, Pb, Sn, Ag, Mg, Au, Zn, Cu, Al, Na, Hg, K is 6. These metals are copper, aluminum, sodium, potassium, magnesium, and zinc.