Why is the atomic number so important?

Related questions

• How can the atomic number be determined?
• How can the atomic mass of an element be calculated?
• How do atomic numbers change in the periodic table?
• What is the atomic mass in hydrogen?
• What does the atomic number tell us?
• Why is the atomic number used to identify elements?
• Why is the atomic number a whole number?
• Why is atomic number represented by Z?
• How did Dmitri Mendeleev contribute to the atomic number?
• How is the atomic number affected by gamma decay?