What can you infer about copper and silver based on the position related to each other on the periodic table

Asingle atom of an element has 21 neutrons, 20 electrons, and 20 protons. which element is it? ok o z

The big bang nucleosynthesis theory states that elements were produced in the first few minutes of the big bang while elements have their origins in the interiors of stars, forming much later in the history of the universe.

When the chemicals iron sulfide (fes) and hydrochloric acid (hcl) are combined, bubbles appear from the mixture. 1. does the appearance of bubbles indicate a physical or chemical change? 2. why do the bubbles indicate this change? 3. what property is this?