Embedded Files
Covalent bonds are the bonds between two nonmetals when they share valence electrons.
Covalent bonds can be polar or nonpolar, meaning that the electrons are shared unequally or equally.
Covalent bonds can be single, double, triple bonds or an average of those if there are resonance structures.
Covalent bonds occur at the lowest energy state. This happens when the attraction between the nuclei is greatest for the shared electrons, but the repulsions between electrons and between the nuclei is the least. If the atoms are too close together the nuclei will repel each other and if they are too far apart the attraction will not be enough to hold them together. This is shown in the graphs below
What is Bond Energy?
What is Bond Energy?
Bond energy is the energy required when breaking a bond, or the energy released when a bond is formed. The magnitude is the same, but the sign is different.
How does the atomic radius and the bond order affect the bond energy of covalent compounds?
How does the atomic radius and the bond order affect the bond energy of covalent compounds?
Larger atomic radii increase the bond length. Longer bond length decreases the bond energy Increasing the bond order (single, double or triple bond) increases the bond energy, as there are more electrons involved and therefore greater Coulombic attraction and the bond length has decreased.
What is Lattice Energy?
What is Lattice Energy?
In Ionic compounds, lattice energy is the energy required to separate ions. It is defined as the change in energy that takes place when gaseous ions are combined to form an ionic solid. Combining ions will release energy (exothermic).
Lattice energy can be represented using a modification of Coulomb's law. Where the energy is proportional to the charges and inversely proportional to the distances between the nuclei.
Larger charges = more attraction = more energy required to separate the ions.
Smaller radii = more attraction = more energy required to separate the ions.
Watch this video to better understand lattice energy of ionic compounds, not that lattice energy is the same as potential energy that we discussed above but it is written using different symbols in the video
Strength of Ionic bonds:
Strength of Ionic bonds:
Stronger ionic bonds have more lattice energy and therefore to break a strong ionic bond you need to apply more energy.
Two factor affect the strength of ionic bonds: The radius of ions and the charge on each ion.
The bigger the charge the stronger the ionic bond is and the smaller the internuclear distance the weaker the ionic bond.
When comparing ionic compounds we look at the charges first. The ionic compound with greater charges will have greater lattice energy and stronger ionic bonds.
Checking for Understanding
Checking for Understanding
Which ionic compound will have bigger lattice energy and stronger bonds NaCl or CaO? Explain
First, let's determine the charges on each ion Na has a +1 charge and Cl has a -1 charge
However, Ca has a +2 charge and O has a -2 charge
Ionic compounds that are formed between ions with bigger charges will have stronger ionic bonds, so we do not need to look further and discuss the radii of each ion we can say CaO has stronger ionic bonds and higher lattice energy .
2. Which ionic compound will have bigger lattice energy and stronger bonds NaCl or LiCl? Explain
Both Na and Li ions have +1 charge. So we can not use the charge to compare lattice energy of LiCl and NaCl. However, Li is smaller than Na because Li has less shells than Na and therefore, the internuclear distance of LiCl is smaller than NaCl. Smaller internuclear distance means stronger ionic bonds and higher lattice energy.
As a result, LiCl has higher lattice energy than NaCl and therefore stronger bonds.
3. Which diatomic molecule has more bond energy Cl2 or O2? Explain
Two factors affect bond energy the internuclear distance between the two bonded atoms and the bond order. In case of Cl2, Cl atoms are sharing a single covalent bond (2 shared electrons), however in O2 there is a double covalent bond between the two Oxygen atom (i.e. 4 shared electrons) and the bigger the bond order the stronger the bond is and the higher the bond energy will be.
Therefore, O2 has a higher bond energy than Cl2
Report abuse