why are BeF2, AlCl3 and BeCl2 covalent compounds and not ionic compounds?
The electronegativity difference between Be and Cl and between Al and Cl just isn't large enough to support ionic behavior. Actually, both compounds are polar covalent which means they do have some ionic character. In a real sense, both Be and Al are small ions and they hold onto their electrons much more than the larger elements do; hence, their electronegativity is higher (which makes the difference between them and Cl smaller). Both Be and Al are exceptions to the rule of eight.
BeF2, AlCl3, and BeCl2 are covalent compounds because they consist of atoms that are held together by covalent bonds, rather than ionic bonds.
In a covalent bond, atoms share one or more pairs of electrons to achieve a stable electron configuration. This usually occurs between nonmetals or between a nonmetal and a metalloid.
In the case of BeF2, which is beryllium fluoride, beryllium is a metalloid and fluorine is a nonmetal. Beryllium has two valence electrons, so it forms two covalent bonds with two fluorine atoms, each of which contributes one electron for sharing.
Similarly, AlCl3, which is aluminum chloride, consists of aluminum, a metal, and chlorine, a nonmetal. Aluminum has three valence electrons, so it forms three covalent bonds with three chlorine atoms, each of which contributes one electron for sharing.
BeCl2, which is beryllium chloride, also contains beryllium, a metalloid, and chlorine, a nonmetal. Beryllium has two valence electrons, so it forms two covalent bonds with two chlorine atoms, each of which contributes one electron for sharing.
In summary, BeF2, AlCl3, and BeCl2 are covalent compounds because the bonding between the atoms involves the sharing of electrons between atoms rather than the transfer of electrons to form ionic bonds.
To understand why BeF2, AlCl3, and BeCl2 are covalent compounds instead of ionic compounds, we need to compare their bonding characteristics.
In general, ionic compounds are formed through the transfer of electrons between a metal and a non-metal, resulting in the formation of positive and negative ions. On the other hand, covalent compounds are formed when atoms share electrons.
In the case of BeF2, AlCl3, and BeCl2, the electronegativity difference between the elements plays a crucial role in determining the bonding type.
BeF2:
Beryllium (Be) has an electronegativity of 1.57, while fluorine (F) has an electronegativity of 3.98. Since the electronegativity difference between Be and F is relatively small, the bond formed is covalent. In BeF2, the beryllium atom shares two electrons with two fluorine atoms, resulting in a stable molecule.
AlCl3:
Aluminum (Al) has an electronegativity of 1.61, and chlorine (Cl) has an electronegativity of 3.16. Similar to BeF2, the electronegativity difference between Al and Cl is not significant, indicating covalent bonding. In AlCl3, aluminum shares three electrons with three chlorine atoms to form a stable molecule.
BeCl2:
Beryllium (Be) has an electronegativity of 1.57, and chlorine (Cl) has an electronegativity of 3.16. Again, the electronegativity difference is relatively small, leading to covalent bonding. In BeCl2, beryllium shares two electrons with two chlorine atoms, resulting in a stable molecule.
In summary, BeF2, AlCl3, and BeCl2 have covalent bonding because the electronegativity differences between the atoms involved are not large enough for the transfer of electrons to occur. Instead, the atoms share electrons to achieve stability and form covalent compounds.