two or more different elements
two or more different elements
Only their no of protons in nucleus (atomic numbers)
Hydrogen and oxygen............. H2O
compound is when two or more elements combine chemically
The main two are hydrogen and helium.
Location
Basically two ways: either by listing all the elements, or by specifying some rule for elements to be included. Listing all the elements only makes sense for finite sets.
That would be the Atomic number. It tells you how many protons are contained in the nucleus of an atom. No two elements could share this number.
The water molecule contains two different elements chemically combined, which makes it a compound. A compound is a pure substance that contains two or more different elements chemically combined.
NaCl Sodium and chlorine - chloride is the name of the ion; chlorine is the element.
silicon and hydrogen