How are the elements in the periodic table primarily arranged?

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

Answer: (C)

Verified step by step guidance

1. Understand that the periodic table is a systematic arrangement of elements based on their properties.
2. Recall that early versions of the periodic table were arranged by increasing atomic mass, but this caused inconsistencies in element grouping.
3. Recognize that the modern periodic table is arranged by increasing atomic number, which is the number of protons in an atom's nucleus.
4. Know that arranging elements by atomic number ensures that elements with similar chemical properties fall into the same groups or columns.
5. Conclude that the primary arrangement of elements in the periodic table is by increasing atomic number, not by alphabetical order, chemical reactivity, or atomic mass.