Question Video: Understanding How the Physical Properties of Group 15 Elements Can Change as We Move down the Periodic Table Chemistry • Second Year of Secondary School

Video Transcript

Which of the following properties is not true for group 15 elements? (A) The melting points decrease down the group. (B) The electronegativity decreases down the group. (C) The metallic property increases down the group. (D) The atomic radii increase down the group. (E) The ionization energy decreases down the group.

This question is asking us to find which of the properties is not true. Let us investigate the trend within the group 15 elements to answer this question.

Let us first investigate atomic radii of the group 15 elements. As the elements in group 15 go down from nitrogen to moscovium, the atomic number increases. The atomic radii increases in size as the atomic number increases only going down a group of elements, such as the group 15 elements. The atomic radii increase down the group is true and is not the correct answer choice.

Now let us take a look at electronegativity within the group 15 elements. Nitrogen is one of the most electronegative elements on the periodic table. Therefore, the electronegativity of group 15 elements must decrease going down the group. So option choice (B), the electronegativity decreases down the group, is not the correct answer choice since the statement is true.

Like electronegativity, ionization energy also decreases down the group 15 elements, since the increase in atomic radii and greater shielding power for valence electrons requires less energy to be removed. Therefore, option choice (E), the ionization energy decreases down the group, is the incorrect answer choice since this is a true statement.

Now let us take a look at the metallic properties of group 15 elements. When moving down group 15 elements, nitrogen and phosphorus are nonmetals, arsenic and antimony are metalloids, and bismuth and moscovium are metals. Therefore, option choice (C), the metallic property increases down the group, is the incorrect answer choice since this statement is true.

Since we know that nitrogen is a nonmetal and bismuth is a metal, bismuth would have the higher melting point. And therefore the melting point would increase going down the group 15 elements. Therefore, option choice (A), the melting points decrease down the group, is the correct answer choice to “Which of the following properties is not true for group 15 elements?”