What Is the Atomic Number?
An element's atomic number (symbolized as Z) is the number of protons found in the nucleus of every atom of that element. This number is a fundamental property that uniquely identifies a chemical element.
Section 2: Key Principles
The atomic number is always a whole number. Since atoms are electrically neutral in their ground state, the atomic number also indicates the number of electrons orbiting the nucleus. This electron count is what primarily governs the element's chemical behavior and bonding.
Section 3: A Practical Example
Consider the element Carbon. Every single atom of carbon in the universe contains exactly 6 protons in its nucleus, so Carbon's atomic number is 6. Similarly, every atom of Oxygen has 8 protons, giving it an atomic number of 8. If an atom had 7 protons, it would be Nitrogen, not Carbon or Oxygen.
Section 4: Importance of the Atomic Number
The atomic number is crucial because the modern periodic table is organized in order of increasing atomic number. This arrangement reveals periodic trends in the elements' properties. An element's atomic number determines its electron configuration and, therefore, its chemical properties and place on the table.