Brass is commonly used to make musical instruments because it is easily malleable and has excellent acoustic properties. it consists of many copper atoms, with some replaced with zinc, as depicted in the image below. what type of alloy is this?

Brass is an alloy, a substitutional alloy to be exact. Substitutional alloying is a type of alloying where certain metallic atom in a crystal structure is replaced with another constituents. Bronze is also a substitutional alloy. Bronze is made up of mostly copper with a mixture of zinc. 

The number of protons in a nucleus

I’m pretty sure it’s false i’m not sure