Question

An atom of an element with two valence electrons reacts with two atoms of an element with atomic number 17 to form an ionic compound. What is the compound MOST LIKELY formed as described? A) CaF2 B) MgCl2 C) CO2 D) BeBr2

Answer 1

The answer will be B) MgCl2 because magnesium has 2 valence electrons and is a metal and chlorine has the atomic number of 17 and is a metal and in order to form an ionic compound, you must have 1 metal and 1 nonmetal

Answer 2

Answer is: B) MgCl2.

Chlorine has atomic number 17, it means it has 17 protons and 17 electrons.

Electron configuration of chlorine atom: ₁₇Cl 1s² 2s² 2p⁶ 3s² 3p⁵.

Chloride is negative ion of chlorine. Chloride is formed when chlorine gain one lectron.

Chloride anion has 17 protons and 18 electrons (like argon-noble gas).

The electron configuration for the chloride ion: ₁₇Cl⁻ 1s²2s²2p⁶3s²3p⁶.

Magnesium has a 2+ oxidation number and chlorine has a 1- oxidation number.  

Magnesium is metal from second group of Periodic table of elements and it lost two electrons to have electron configuration as closest noble gas neon (₁₀Ne), chlorine is nonmetal from 17. group of Periodic table and it gains one electron to have electron configuration as argon (₁₈Ar).