Question Video: Recalling the Meaning of a Group in the Periodic Table | Nagwa

Video Transcript

Which of the following best describes a group in the periodic table? (A) All nonmetals, (B) a collection of elements in a single row, (C) a collection of elements in a single column, (D) a collection of elements in a single diagonal, or (E) all elements with a specific number of neutrons in their nuclei.

The periodic table is a diagram which displays all 118 known elements organized in a very specific order. The location of each element on the periodic table provides a lot of useful information about that element. To answer this question, we need to determine which of the statements provided best describes a group in the periodic table. A group can be defined as a collection of elements with similar chemical or electronic properties. Atoms of elements which are found in the same group typically have the same number of valence or outermost electrons. Let’s zoom in on a section of the periodic table and see if we can determine a relationship between the position of some of the elements and the number of valence electrons an atom of each element has.

To help us find a relationship, we can draw a Bohr model of an atom for each element. In the Bohr model, each circle around the nucleus represents an electron shell. Each electron shell can hold a certain number of electrons. The first electron shell can hold a maximum of two electrons. The second electron shell can hold a maximum of eight electrons. And the third electron shell can hold a maximum of 18 electrons. However, 10 of those electrons are only added to this electron shell when the atoms get bigger. So we sometimes say that the third electron shell can only hold a maximum of eight electrons.

In the diagram, electrons are represented by blue dots, and the electrons found in the outermost electron shell are the valence electrons. To draw a Bohr model of an atom of these six elements, we need to know how many electrons each atom has. The atomic number written above each chemical symbol indicates the number of protons in all atoms and ions of that element. It also indicates the number of electrons in a neutral atom. With this in mind, let’s construct a Bohr model for an oxygen atom, which has eight electrons. The first two electrons will occupy the innermost electron shell, and the remaining six electrons will occupy the second shell. An atom of sulfur has 16 electrons. Two electrons occupy the first electron shell, eight electrons occupy the second electron shell, and six electrons occupy the third electron shell.

Here are the completed Bohr models of an atom of fluorine, chlorine, neon, and argon. If we look at the outermost electron shells of each atom, we can see that atoms of elements that are found in the same column on the periodic table have the same number of valence electrons. As elements in the same group tend to have the same number of valence electrons, we can conclude that a group is a collection of elements found in the same column on the periodic table. Thus, the statement which best describes a group in the periodic table is statement (C) a collection of elements in a single column.