How are the elements in the modern periodic table arranged?

• A. By their chemical reactivity
• B. By alphabetical order of element names
• C. In order of increasing atomic number
• D. In order of increasing atomic mass

Answer: (C)

Verified step by step guidance

1. Understand that the modern periodic table is organized based on a fundamental property of atoms called the atomic number, which is the number of protons in the nucleus of an atom.
2. Recall that earlier versions of the periodic table were arranged by increasing atomic mass, but this led to inconsistencies in element properties.
3. Recognize that arranging elements by increasing atomic number resolves these inconsistencies and groups elements with similar chemical properties into columns called groups or families.
4. Note that chemical reactivity and alphabetical order are not used for the arrangement because they do not reflect the underlying atomic structure or periodic trends.
5. Therefore, the elements in the modern periodic table are arranged in order of increasing atomic number, which reflects the periodic law and the repeating patterns of chemical properties.