(ii) What particle is represented by ●? (iii) What is the central part of the atom called that contains both and ●?
(b) Use the model to explain why the six electrons are arranged as shown.

Answercreating graphs and performing calculations;

According to arrhenius theory of acid and bases, an acid is a proton donor, while base donates hydroxyl ions. further, acid and base reacts to form salt and water.consider following example.hcl    +      h2o          →      cl-          +      h3o+here, hcl has donated a proton, hence it is an acid.now consider following reactionhcl      +      naoh            ↔      nacl      +        h2oin this reaction, hcl donates proton, hence it is acid. on other hand, naoh donates hydroxyl ion (i.e. hence it is a base.   

The basic unit of a chemical element