International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

How are elements in the Periodic Table arranged?

1. In order of decreasing atomic mass

2. In order of increasing atomic number

3. In alphabetical order

4. By the total number of electrons

The correct answer is: In order of increasing atomic number

The elements in the Periodic Table are arranged in order of increasing atomic number, which corresponds to the number of protons in each element's nucleus. This arrangement reflects the periodic law, which states that the properties of the elements are a periodic function of their atomic numbers. By organizing elements according to atomic number, the table highlights trends in elemental properties, such as reactivity and electronegativity, making it easier to predict how different elements will behave chemically. This systematic approach allows for a clearer understanding of the relationships among different elements, showcasing periodicity in both physical and chemical properties as you move across a period or down a group in the table. Arranging elements by decreasing atomic mass would not reflect their chemical behaviors accurately, as isotope distribution can vary among elements. Alphabetical ordering does not convey any scientific information regarding the elements' behaviors or properties. Organizing by the total number of electrons could lead to confusion, as electron configurations can be similar for different elements, especially among noble gases, alkali metals, and their corresponding periods.