How is the “Modern Periodic Table” organized?
A increasing charge number
B increasing atomic mass
C alphabetical order
D increasing atomic number
The correct answer and explanation is:
The correct answer is D) increasing atomic number.
The modern periodic table is organized by increasing atomic number, not by atomic mass or alphabetical order. The atomic number refers to the number of protons in an atom’s nucleus. This organization was first proposed by Dmitri Mendeleev in 1869, who arranged elements based on their atomic masses. However, he noticed that when elements were ordered by mass, certain properties repeated periodically. This led to the discovery that elements with similar properties appeared at regular intervals.
In 1913, Henry Moseley refined this idea by using the atomic number instead of atomic mass. Moseley’s work showed that the periodic law, which states that the properties of elements repeat at regular intervals when arranged by increasing atomic number, was more accurate than Mendeleev’s atomic mass-based arrangement. This corrected the problem of elements like iodine and tellurium, where Mendeleev had placed iodine before tellurium based on atomic mass, even though tellurium had similar properties to iodine’s neighbors.
By organizing elements according to their atomic number, the periodic table reflects a more accurate pattern of properties. Elements in the same column (group) share similar chemical behaviors due to their similar electron configurations, especially in the outermost shells. For example, all noble gases (group 18) are inert because they have full outer electron shells. As you move from left to right across a period, the number of protons and electrons increases, affecting the element’s chemical reactivity and other properties.
This system has made the periodic table an invaluable tool in chemistry, allowing scientists to predict the behavior of elements and their compounds. The modern table is also arranged into blocks, with s, p, d, and f blocks that further categorize elements based on their electron configurations.