Final answer:
The net charge of a system with 8 electrons and 18 protons is +10 elementary charge units, because each proton has a charge of +1 and each electron has a charge of -1.
Step-by-step explanation:
To find the net charge of a system with 8 electrons, 18 protons, and 4 neutrons, we need to consider the charges of electrons and protons. Since electrons have a negative charge (-1) and protons have a positive charge (+1), we can calculate the charge by subtracting the number of electrons from the number of protons. Neutrons do not carry a charge and thus do not affect the net charge.
The formula to find the net charge (Q) is:
Q = (Number of protons) - (Number of electrons)
Substituting the given values:
Q = 18 protons - 8 electrons
Q = 10
Since the charge of a single proton or electron is 1 elementary charge unit, the net charge of the system would be +10 elementary charge units, or +10e, where 'e' is the symbol for the elementary charge.