--- ## [[Covalent bond]] - A covalent bond is a bond between two atoms means that those two atoms are sharing at least **one pair of [[Valence Electrons]] electrons**. - It usually occurs between two **non metallic** elements. - The reason why covalent bonds occur naturally in some elements is because the energy H of the system of bonded atoms is lower then the energy of those non-bonded elements. > **Covalent bonds form what is known as a molecule.** >[! Covalent bond image] >![[Files/Covalent Bond img.png]] --- ## [[Ionic Bond]] - This is an when a difference in **charge** between two atoms causes them to bond due to an [[electrostatic force]]. - In an [[Ionic Bond]] an [[Electrons]] is transferred from one atom to another. - Usually occurs between metallic atoms or **[[Ion]] with opposing charges**. > **Ionic bonds form compounds.** >[! Ionic bond image] >![[Atomic Bonding.png]] --- ## Reason for bonding - Elements want to fill their [[Valence Electrons |Valence shell]] by bonding to other elements. Noble gasses already have a filled valence shell. - Elements on the right of the periodic table have **too few** electrons in their valence shell and elements on the left side of the periodic table have **too many** electrons which is why they often bond with each other **covalently** to fill their [[Valence Electrons |Valence shell]]. --- ## Energy needed to break/form bonds - The energy needed to break/form a bond is known as the **bond dissociation energy**. - The bond dissociation energy **increases** towards the bottom left side of the periodic table because those elements have a **smaller atomic radius** and **a lower electron affinity**. > [!tip] > ##### General rule: > - **The closer two atoms are in a bond the more energy it will take to break it.** - The **more bonds** two atoms share *(double, triple)* the closer they are and thus the more energy it will take to break that bond. ### Finding the change in heat of a reaction (enthalpy) - Add together the bond dissociation energies for all broken and formed bonds then subtract those two results to find the overall change in energy of a reaction. - If the change in energy is **negative it is exothermic and endothermic otherwise**. > [! Enthalpy equation example] > <br> > > ![[Atomic bonding enthlypy.png]] --- ## Effect of electronegativity - The difference in **electronegativity** between two bonding atoms can be used to determine what kind of bond they have formed. - The greater the difference the greater the **ionic character**. > [! Electronegativity and bonds] > <br> > > - **NOTE:** In pure covalent bonds, the electrons are shared equally. In polar covalent bonds, the electrons are shared unequally. > <br> > > - ![[Pasted image 20230120131418.png]] --- #mainpage