What is meant by endothermic reactio

The reaction in heat is absorbed by the system from the surrounding is called endothermic reaction.

Hope this helps, have a great day ahead!

An endothermic reaction happens when a high amount of energy is needed in order for old bonds to break and is then released to form new bonds. The energy can come in many forms but the most common energy form used for this process is heat.

Common examples of endothermic reactions are photosynthesis, melting ice, melting solid salts, or evaporating liquid water.

Where is the graph ?

You use the atomic number to find out how many protons and neutrons there are in the atom. you use the atomic mass to find out how many protons and electrons there are in the atom.