Utah Esthetician State Board Practice Exam

What is the significance of having an equal number of protons and electrons in an atom?

1. It determines the atomic weight

2. It indicates a stable electrical charge

3. It defines the chemical reactivity

4. It assesses the atomic radius

The correct answer is: It indicates a stable electrical charge

Having an equal number of protons and electrons in an atom signifies a stable electrical charge. Protons are positively charged particles, while electrons carry a negative charge. When these two are balanced, the positive and negative charges cancel each other out, resulting in a neutral atom. This neutrality is important for the stability of the atom and impacts its interactions with other atoms. An unbalanced charge, caused by either excess protons or electrons, would lead to an ionized state, which can affect the atom's behavior in chemical reactions and its ability to bond with other atoms. In contrast, atomic weight is determined by the total number of protons and neutrons, which does not directly relate to the balance of protons and electrons. Similarly, chemical reactivity is influenced by the electrons in the outermost shell, particularly their arrangement, rather than the overall balance of protons and electrons. Finally, atomic radius involves the size of the atom itself, which is not determined by the equality of protons and electrons, but rather by the forces pulling electrons closer to the nucleus and the electron configuration.