In the periodic table, elements are arranged in order of increasing what?

The correct choice indicates that the elements in the periodic table are arranged in order of increasing atomic number. The atomic number of an element is defined as the number of protons found in the nucleus of an atom of that element. This fundamental property not only uniquely identifies each element but also determines its position in the periodic table.

Arranging elements by atomic number reflects their increasing proton count, which correlates with both the element's electron configuration and its chemical properties. As you move from left to right across a period, the atomic number increases, leading to changes in behavior and reactivity of the elements. This arrangement allows for the periodic trend observed in properties such as ionization energy, electronegativity, and atomic radius, which follow distinct patterns based on the position of the element.

Other options, such as atomic mass, electronegativity, and density, do not provide a clear or consistent organization for the periodic table. Atomic mass, for instance, can vary due to the presence of isotopes and does not consistently increase in the same way that atomic numbers do. Electronegativity is a property that varies with the arrangement of the elements, and density is influenced by both atomic mass and atomic volume, making them less suitable for the purpose of