Final answer:
Potassium is in Group 1 and Period 4. Hydrogen and helium are gaseous elements within the first 20 elements, and hydrogen is the lightest element. The element names for the given symbols are silver, zinc, and lead.
Step-by-step explanation:
(i) Potassium is located in Group 1 and Period 4 of the periodic table. Its group number indicates that it belongs to the alkali metals, while its period number tells us that it is in the fourth row of elements.
(ii) Two gaseous elements within the first 20 elements are hydrogen (H) and helium (He).
(iii) Hydrogen (H) is the lightest element within the first 20 elements with a mass of approximately 1 atomic mass unit (AMU).
(iv) The element names of the given symbols are:
- Ag - Silver
- Zn - Zinc
- Pb - Lead
Learn more about Position of elements in the periodic table