Protons, neutrons, and electrons are important parts of atoms that help decide how elements behave.

1. Protons:

   • Every element has a special number of protons, called the atomic number (we write it as $Z$).
   • For example, hydrogen has 1 proton, so its atomic number is $Z = 1$. Carbon, on the other hand, has 6 protons, giving it $Z = 6$.
   • The number of protons tells us what the element is and where it is found on the periodic table.

2. Neutrons:

   • Neutrons help make up the mass of an element but don’t directly change how it behaves chemically.
   • Some elements can have the same number of protons but a different number of neutrons. These are called isotopes.
   • For instance, carbon-12 (which we can write as $C^{12}$) has 6 neutrons, while carbon-14 ($C^{14}$) has 8 neutrons.

3. Electrons:

   • Electrons play a key role in how an atom reacts with other atoms.
   • The way electrons are arranged in energy levels or shells affects how atoms bond together.
   • Elements that are in the same group on the periodic table have similar chemical properties because they have similar arrangements of electrons.
   • For example, the alkali metals in Group 1 all behave in a similar way.

Understanding protons, neutrons, and electrons helps us learn more about the elements and their reactions!