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

Which of the following best describes both a Group and a Period in the periodic table?

1. Group is a horizontal row; Period is a vertical column

2. Group has the same number of protons; Period has the same atomic mass

3. Group is a vertical column; Period is a horizontal row

4. Group and Period both represent different states of matter

The correct answer is: Group is a vertical column; Period is a horizontal row

The correct answer is that a Group is a vertical column; Period is a horizontal row. In the periodic table, elements are organized in such a way that each column, or Group, contains elements that share similar chemical properties and often have the same number of valence electrons. This similarity arises because elements in the same Group react in comparable ways, developing analogous chemical behavior. On the other hand, each horizontal row, or Period, corresponds to elements that have the same number of electron shells. As you move across a Period from left to right, the atomic number increases, indicating that each subsequent element has an additional proton and electron compared to the previous element. This organization effectively illustrates periodic trends, such as electronegativity, ionization energy, and atomic radius, making it a foundational element of chemistry education. The other options do not accurately define Groups and Periods. Groups do not specifically relate to proton numbers in the way the second option suggests, as not all elements in a Group have the same number of protons—only their properties are similar. Similarly, both Groups and Periods do not represent different states of matter, as indicated in the last option. Therefore, option C accurately captures the organization of elements in the periodic table.