Electrons carry a negative electric charge of approximately −1.602 × 10⁻¹⁹ coulombs (C). This tiny quantity is known as the elementary charge, and it represents the smallest unit of electric charge that is observed in nature on free particles.

The electron’s charge is fundamental, meaning it is not made up of smaller charges—it’s a basic building block of electric charge. The value is always the same for every electron, making it one of the key constants in physics.

This negative charge is crucial in many physical processes:

• In atoms, electrons orbit the positively charged nucleus, and their negative charge balances the positive charge of protons to make the atom electrically neutral.
• In electric circuits, the flow of electrons constitutes electric current, moving from the negative terminal toward the positive terminal of a power source (though by convention, current is described as flowing the opposite way).
• In chemistry, the transfer or sharing of electrons between atoms leads to the formation of chemical bonds.

The charge of the electron was first measured in the early 20th century by Robert Millikan through the famous oil-drop experiment, which helped establish the discrete, quantized nature of electric charge.