Protons, which carry a positive electrical charge, and neutrons, which have no charge, reside together in the dense center known as the nucleus. Surrounding this nucleus is a cloud of much lighter electrons, each carrying an equal but opposite negative charge. The number of protons inside the nucleus defines the element, a value referred to as the atomic number.
The Balanced Core: Protons, Electrons, and the Neutral Atom
An atom is normally found in an electrically neutral state, carrying no net electrical charge. This neutrality is achieved because the number of positively charged protons must exactly match the number of negatively charged electrons. Since the charge magnitude of a single proton equals that of a single electron, these opposite charges cancel each other out.
For example, sodium has an atomic number of 11, meaning it contains 11 protons. In its neutral form, this sodium atom must also possess 11 electrons orbiting the nucleus to maintain a zero net charge. The fixed number of protons dictates the element’s identity, while the balance with electrons determines its charge state.
Creating Charge: How Atoms Become Ions
Atoms can gain or lose electrons, a process called ionization, which results in a net electrical charge. This electron transfer occurs because atoms often seek a more stable electron configuration, which usually involves completing their outermost electron shell. Importantly, the number of protons within the nucleus remains constant during this chemical process.
Because the number of protons defines the element, changing the proton count would transform the atom into a different element, which only happens in nuclear reactions. Therefore, when an atom is chemically altered, only the number of electrons is adjusted. A charged atom created by this gain or loss of electrons is referred to as an ion.
Cations Explained: The Proton-Electron Comparison
A cation is an ion that carries a net positive electrical charge. This positive charge arises when a neutral atom loses one or more of its negatively charged electrons.
In a cation, the number of protons is always greater than the number of electrons. The positive charge of the fixed number of protons is no longer completely offset by the reduced number of negative electrons. The resulting positive charge of the cation is numerically equal to the number of electrons that were lost.
Consider the sodium ion, written as Na+, which is a common cation. The neutral sodium atom starts with 11 protons and 11 electrons. When it forms the Na+ ion, it loses one electron, leaving it with 11 protons but only 10 electrons. The single extra proton results in a net charge of positive one.