Answer:
radical
Explanation:
A radical is group of atoms. Some common examples of radicals are the OH- (hydroxide ion), NO₃⁻ (nitrate ion) and more.
Cu + 2HNO₃ →Cu(NO₃)₂ + H₂
In this single replacement reaction, the nitrate ion (NO₃⁻) which is the radical is replaced from nitric acid to form copper nitrate.
