Cells contain many water. One of the roles of the water is to disresolve various products. For instance, there are many kind of different ionic compounds (salts) in cells. Ions are provided to maintain cell potentials and are crucial in cell signaling and muscle contraction.

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How deserve to you tell if a compound is ionic or covalent?

There is not a simple answer to this question. Many bonds are somewright here in between. In a polar covalent bond, a pair of electrons is shared between two atoms in order to fulfill their octets, however the electrons lie closer to one end of the bond than the other. Tright here is more negative charge towards one finish of the bond, and also that leaves even more positive charge at the other end.

Looking at the electronegativity worths of various atoms helps us to decide exactly how evenly a pair of electrons in a bond is common. Electronegativity boosts toward the top ideal hand corner of the routine table bereason of a combination of nuclear charge and also shielding factors. Atoms in the top right hand also corner of the periodic table have a greater pull on their shared bonding electrons, while those in the lower left hand edge have actually a weaker attraction for the electrons in covalent bonds.

In a carbon-oxygen bond, more electrons would be attracted to the oxygen because it is to the ideal of carbon in its row in the periodic table. Compounds prefer , dimethyl ether, CH3OCH3, are a little bit polar. Formaldehyde, CH2O, is also more polar. Electrons in pi bonds are hosted more loosely than electrons in sigma bonds, for factors entailing quantum mechanics. That enables the oxygen to pull the electrons toward it even more quickly in a multiple bond than in a sigma bond.


Not all polarities are simple to identify by glancing at the periodic table. The direction of the dipole in a boron-hydrogen bond would certainly be difficult to predict without looking up the electronegativity worths, since boron is additionally to the best however hydrogen is higher up. As it transforms out, the hydrogen is slightly negative.

A bond is ionic if the electronegativity difference in between the atoms is great enough that one atom can pull an electron entirely away from the various other one. That situation is prevalent in compounds that combine facets from the left-hand also edge of the regular table (sodium, potassium, calcium, etc.) through elements in the excessive upper best hand also corner of the periodic table (most typically oxygen, fluorine, chlorine). Sodium chloride is an ionic compound.

Many kind of bonds can be covalent in one instance and ionic in one more. For instance, hydrogen chloride, HCl, is a gas in which the hydrogen and also chlorine are covalently bound, but if HCl is bubbled into water, it ionizes totally to give the H+ and Cl- of a hydrochloric acid solution. Even in gaseous HCl, the charge is not dispersed evenly. The chlorine is partially negative and the hydrogen is partially positive.


Potassium hydroxide, KOH, has one bond that is covalent (O-H) and one that is ionic (K-O). Hydrogen is tricky bereason it is at the top of the routine table and the left side. It is simply electropositive sufficient to create ionic bonds in some situations. It is just electronegative enough to create covalent bonds in various other instances.


Due to the fact that it is so common that an facet from the extreme left hand of the regular table is current as a cation, and that elements on the too much right lug negative charge, we have the right to regularly assume that a compound containing an instance of each will certainly have at least one ionic bond.

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Exercise (PageIndex3)

Ammonium ion, NH4+, is a common molecular ion. Draw structures for the complying with compounds that include this ion.