Question

19\. Which bond in each of the following pairs has the greater ionic character? a. \(\mathrm{Na}-\mathrm{F}\) or \(\mathrm{Na}-\mathrm{I}\) b. \(\mathrm{Ca}-\mathrm{S}\) or \(\mathrm{Ca}-\mathrm{O}\) c. \(\mathrm{Li}-\mathrm{Cl}\) or \(\mathrm{Cs}-\mathrm{Cl}\) d. \(\mathrm{Mg}-\mathrm{N}\) or \(\mathrm{Mg}-\mathrm{P}\)

Short answer

In summary, a. \(\mathrm{Na}-\mathrm{F}\) bond has greater ionic character b. \(\mathrm{Ca}-\mathrm{O}\) bond has greater ionic character c. \(\mathrm{Cs}-\mathrm{Cl}\) bond has greater ionic character d. \(\mathrm{Mg}-\mathrm{N}\) bond has greater ionic character

Step-by-step solution

Find electronegativity values

First, we find the electronegativity values for each atom involved in the bonds. These can be found in any standard periodic table or chemistry reference. Electronegativity values: Na: 0.93 F: 3.98 I: 2.66 Ca: 1.00 S: 2.58 O: 3.44 Li: 0.98 Cl: 3.16 Cs: 0.79 Mg: 1.31 N: 3.04 P: 2.19

Calculate electronegativity differences

With the electronegativity values found, we now need to calculate the electronegativity differences for each bond pair. The difference is simply the absolute value of the difference between the electronegativity values of the two atoms in the bond. a. Na-F: |3.98 - 0.93| = 3.05 Na-I: |2.66 - 0.93| = 1.73 b. Ca-S: |2.58 - 1.00| = 1.58 Ca-O: |3.44 - 1.00| = 2.44 c. Li-Cl: |3.16 - 0.98| = 2.18 Cs-Cl: |3.16 - 0.79| = 2.37 d. Mg-N: |3.04 - 1.31| = 1.73 Mg-P: |2.19 - 1.31| = 0.88

Determine which bond has a greater ionic character

Now, we can see which bond in each pair has a greater electronegativity difference, and hence, a greater ionic character. a. Na-F (3.05) > Na-I (1.73) -> Na-F has a greater ionic character b. Ca-O (2.44) > Ca-S (1.58) -> Ca-O has a greater ionic character c. Cs-Cl (2.37) > Li-Cl (2.18) -> Cs-Cl has a greater ionic character d. Mg-N (1.73) > Mg-P (0.88) -> Mg-N has a greater ionic character In summary, a. \(\mathrm{Na}-\mathrm{F}\) bond has greater ionic character b. \(\mathrm{Ca}-\mathrm{O}\) bond has greater ionic character c. \(\mathrm{Cs}-\mathrm{Cl}\) bond has greater ionic character d. \(\mathrm{Mg}-\mathrm{N}\) bond has greater ionic character

Key concepts

Electronegativity

Electronegativity is a fundamental concept in chemistry that describes the tendency of an atom to attract electrons toward itself when it is chemically combined with another atom. The scale of electronegativity values ranges from caesium and francium, which have very low values, to fluorine, which holds the highest value on the scale.

The importance of electronegativity lies in its ability to predict the nature of chemical bonds. When two atoms with a large difference in electronegativity values form a bond, the electrons are not shared equally between them. This leads to the formation of an ionic bond, wherein one atom (with higher electronegativity) gains electron(s) and becomes negatively charged, while the other (with lower electronegativity) loses electron(s) and becomes positively charged.

For example, in the bond between sodium (Na) and fluorine (F), the difference in their electronegativity values is significant, leading to a strong ionic bond with a high ionic character. On the other hand, a bond between two atoms with similar electronegativity values, like nitrogen (N) and phosphorus (P), would share electrons more equally, resulting in a bond with covalent character.

Chemical Bonds

Chemical bonds are the attractive forces that hold atoms together in molecules or compounds. There are three primary types of chemical bonds: ionic, covalent, and metallic. Ionic bonds, as mentioned, occur when there is a large difference in electronegativity between two atoms, causing one atom to transfer its electron(s) to another, forming ions.

Covalent bonds occur when two atoms with similar electronegativity values share one or more pairs of electrons. This bond is typically stronger than an ionic bond due to the direct overlap of orbitals. Finally, metallic bonds involve the sharing of free electrons amongst a lattice of metal atoms.

Factors Influencing Ionic Character

By understanding electronegativity, we can predict the ionic character of a bond. The greater the difference in electronegativity, the greater the ionic character of the bond. For example, the bond between calcium (Ca) and oxygen (O) has more ionic character than the bond between calcium (Ca) and sulfur (S), because the electronegativity difference is greater for Ca-O.

Periodic Table

The periodic table is more than just a chart of elements; it is a map of chemical behavior. Elements in the periodic table are organized by increasing atomic number (number of protons) and by chemical properties. One of the most critical properties that vary across the periodic table is electronegativity, which increases from left to right and bottom to top.

Thus, understanding the layout of the periodic table can help predict electronegativity values and consequently, the type of bonding that might occur between different elements. For instance, alkali metals like sodium (Na) and caesium (Cs) reside on the far left of the periodic table and have lower electronegativity values, while non-metals like fluorine (F) and chlorine (Cl) are found on the right side and have higher electronegativity values.

This structuring explains why Na and Cs form ionic bonds with F and Cl, respectively, as seen in the textbook solutions involving compounds like Na-F and Cs-Cl. The vast difference in their positions in the periodic table reflects a vast difference in their ability to attract electrons, resulting in a bond with significant ionic character.