Question Video: Identifying Unknown Element Forming an Ionic Bond from a Lewis Structure | Nagwa Question Video: Identifying Unknown Element Forming an Ionic Bond from a Lewis Structure | Nagwa

Question Video: Identifying Unknown Element Forming an Ionic Bond from a Lewis Structure Chemistry • Second Year of Secondary School

Join Nagwa Classes

Attend live Chemistry sessions on Nagwa Classes to learn more about this topic from an expert teacher!

Element X can form an ionic bond with oxygen. From the Lewis structure illustrated below, which of the following elements can be X? [A] H [B] N [C] F [D] Na [E] Al

05:44

Video Transcript

Element X can form an ionic bond with oxygen. From the Lewis structure illustrated below, which of the following elements can be X? (A) H, (B) N, (C) F, (D) Na, or (E) Al.

Unknown element X is forming an ionic bond. Ionic bonds are formed from the strong electrostatic attractions between positively and negatively charged ions. These ions can often be formed from the transfer of valence electrons. The question provides a Lewis structure showing two atoms of element X and one oxygen atom engaging in ionic bonding. A Lewis structure is a simple schematic illustration that shows how valence shell electrons are shared or exchanged between atoms in covalently or ionically bonded compounds.

In Lewis structures, dots can be used to represent valence electrons. The Lewis structure shows each atom of element X with one valence electron. The arrows show that each atom of element X loses its single valence electron and these two valence electrons are gained by the oxygen atom, resulting in the formation of one plus cations of element X and an oxide anion with a charge of two minus. This transfer of electrons from element X to oxygen can be understood through the octet rule of thumb, which tells us that in many cases atoms tend to lose, gain, or share electrons to achieve eight electrons in their outer shell. This tendency can be predicted using the number of valence electrons an atom has and thus its group number on the periodic table.

Let’s first locate oxygen on the periodic table to confirm this idea. By determining an element’s group or column on the periodic table, we can also determine the number of valence electrons it has. In this question, we will not address this relationship for elements in groups three through 12. Oxygen, atomic number eight, is found in group 16 on the periodic table, which means it has six valence electrons, as indicated by the Lewis structure. To achieve eight electrons, in its outer shell, oxygen will gain two more valence electrons and become an oxide ion with a two minus charge. While we don’t know the identity of element X, the Lewis structure shows us that element X has one valence electron, which it loses to form an ion with a one plus charge. Thus, element X must be found in group one of the periodic table.

Let’s have a look at our answer choices to find the element that matches this description. Answer choice (A) H is the chemical symbol for hydrogen, which is atomic number one and can be found in group one of the periodic table. Hydrogen has one valence electron. Answer choice (B) N is the chemical symbol for nitrogen, which is atomic number seven and can be found in group 15 of the periodic table. Nitrogen has five valence electrons. Answer choice (C) F which is the chemical symbol for fluorine, which is atomic number nine and can be found in group 17 of the periodic table. Fluorine has seven valence electrons. Answer choice (D) Na is the chemical symbol for sodium, which is atomic number 11 and can be found in group one of the periodic table. Sodium has one valence electron.

Finally, answer choice (E) Al is the chemical symbol for aluminum, which is atomic number 13 and can be found in group 13 of the periodic table. Aluminum has three valence electrons. We can eliminate answer choices (B), (C), and (E) since these elements do not have one valence electron and cannot be element X. Hydrogen and sodium both have one valence electron. To determine which could be element X, we need to determine how these elements would bond with oxygen. As hydrogen is a nonmetal, when bonding with another nonmetal such as oxygen, a covalent bond will be formed. If two hydrogen atoms bond with one oxygen atom, one of the most important molecules on our planet is formed, water.

Alternatively, since sodium is a metal, when reacting with the nonmetal oxygen, it will lose electrons. For every one oxygen atom to achieve eight electrons in its outer shell, two sodium atoms are needed. This would form ionic bonds between one oxide ion for every two sodium ions. This matches what we see with unknown element X. Therefore, the element that can be element X from the Lewis structure is answer choice (D) Na.

Join Nagwa Classes

Attend live sessions on Nagwa Classes to boost your learning with guidance and advice from an expert teacher!

  • Interactive Sessions
  • Chat & Messaging
  • Realistic Exam Questions

Nagwa uses cookies to ensure you get the best experience on our website. Learn more about our Privacy Policy