The outermost energy shell of an atom
because they are involved in forming bonds
TL;DR: The make of an aircraft is the name of the designer (for example, Boeing) and the model of an aircraft (also called the type) is the designation for the general design of the aircraft (for example, 737). It looks like "basic model" is just an older term for "model".
Answer:
A. Students made a measurement error, because ending with more products is impossible.
Explanation:
The law of conversation of matter tells us that in a chemical reaction, matter is never created or destroyed, it's simply converted from one form to another. So the mass of reactants should always equal the mass of the products in a chemical reaction. If there is excess mass in the product, the students have made an error of some kind.