two elements have the following # of electrons: K=19 & F=9. What kind of bond will they form & what is the formula of the resulting compound? A. Ionic, KF B. Covalent, KF C. Ionic, KF2 D. Polar covalent, KF2 E. Hydrogen, KF
The Correct Answer and Explanation is:
The two elements in question are K (Potassium) with 19 electrons and F (Fluorine) with 9 electrons.
- Electron Configuration and Bond Type:
- Potassium (K) is an alkali metal with an electron configuration of [Ar] 4s¹. Potassium has one electron in its outermost shell, which it can easily lose to achieve a stable electron configuration, similar to noble gases.
- Fluorine (F) is a halogen with an electron configuration of [He] 2s² 2p⁵. Fluorine has seven electrons in its outer shell and needs one more electron to complete its valence shell, achieving the stable electron configuration of a noble gas (Neon).
Given these electron configurations, K will lose its single valence electron, and F will gain it. This creates an ion pair: Potassium becomes a K⁺ ion (positive charge) and Fluorine becomes an F⁻ ion (negative charge).
- Ionic Bond Formation:
Since Potassium is a metal and Fluorine is a nonmetal, they will form an ionic bond. Ionic bonds typically form when a metal atom donates electrons to a nonmetal atom, creating oppositely charged ions that are attracted to each other by electrostatic forces. - Formula of the Compound:
When K loses one electron and F gains one, the simplest ratio of potassium ions to fluorine ions will be 1:1. Thus, the resulting ionic compound will have the formula KF. - Conclusion:
The correct answer is A. Ionic, KF because Potassium (K) and Fluorine (F) will form an ionic bond, and the chemical formula of the resulting compound is KF.
Why the Other Choices are Incorrect:
- B. Covalent, KF: Covalent bonds occur between nonmetals sharing electrons, not between a metal and a nonmetal.
- C. Ionic, KF₂: There’s no need for two fluoride ions to balance the charge of one potassium ion.
- D. Polar covalent, KF₂: Polar covalent bonds are a type of covalent bond between two nonmetals with different electronegativities, but potassium and fluorine will form an ionic bond, not covalent.
- E. Hydrogen, KF: Hydrogen bonds occur between molecules, not within ionic compounds.
Thus, A. Ionic, KF is the correct answer.
