A sample of matter must be copper if (1) each atom in the sample has 29 protons

(2) atoms in the sample react with oxygen

(3) the sample melts at 1768 K

(4) the sample can conduct electricity

The answer is 1. Copper is an element with sign Cu and atomic number 29 which means that there are 29 protons in this element. It is a soft, flexible, and elastic metal with very extraordinary thermal and electrical conductivity. A newly unprotected exterior of pure copper has a reddish-orange color.