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chemical bonding
chemical bonding
Chemical bonds lie on a continuum and involve electrons in the valence shell.
Chemical bonds lie on a continuum and involve electrons in the valence shell.
electronegativity
electronegativity
covalent bonds
covalent bonds
In covalent bonds electrons are shared between adjacent nuclei so the atoms have full valence shells - they are now more stable and at a lower energy state. Covalent bonds occur between two non metals, and can be single, double or triple.
In covalent bonds electrons are shared between adjacent nuclei so the atoms have full valence shells - they are now more stable and at a lower energy state. Covalent bonds occur between two non metals, and can be single, double or triple.
Single bonds share two electrons - one from each atom, such as Cl₂. They are the weakest and longest bonds
Single bonds share two electrons - one from each atom, such as Cl₂. They are the weakest and longest bonds
Double bonds share 4 electrons - two from each atom, such as O₂
Double bonds share 4 electrons - two from each atom, such as O₂
Triple bond share 6 electrons - three from each atom, such as N₂
Triple bond share 6 electrons - three from each atom, such as N₂
Most covalent bonds show a difference in electronegativity and exhibit some polarity. Bonds between the same atoms obviously have the same electronegativity and are pure non-polar covalent bonds - any dipoles are temporarily induced. Even though the bond continuum shows non-polar bonds as having a difference in electronegativity of <0.4/0.5 it is safe to assume that all bonds except those between diatomic atoms exhibit some polarity.
Most covalent bonds show a difference in electronegativity and exhibit some polarity. Bonds between the same atoms obviously have the same electronegativity and are pure non-polar covalent bonds - any dipoles are temporarily induced. Even though the bond continuum shows non-polar bonds as having a difference in electronegativity of <0.4/0.5 it is safe to assume that all bonds except those between diatomic atoms exhibit some polarity.
Polar covalent bonds occur where electrons are not shared equally between two atoms. Therefore there is a permanent difference in the dipoles and the molecule will be a polar molecule, if that is the only bond. On the bond continuum these bonds have a difference in electronegativity of 0.5 - 1.6 .
Polar covalent bonds occur where electrons are not shared equally between two atoms. Therefore there is a permanent difference in the dipoles and the molecule will be a polar molecule, if that is the only bond. On the bond continuum these bonds have a difference in electronegativity of 0.5 - 1.6 .
Below is an illustration of the difference between non-polar and polar covalent bonds.
Below is an illustration of the difference between non-polar and polar covalent bonds.
On the bond continuum ionic bonds have a difference in electronegativity of >1.6-2.0.
On the bond continuum ionic bonds have a difference in electronegativity of >1.6-2.0.
ionic bonds
ionic bonds
Ionic bonds occur between a metal and a non metal, in which electrons are transferred from the metal ion to the non metal ion.
Ionic bonds occur between a metal and a non metal, in which electrons are transferred from the metal ion to the non metal ion.
Thinking back to electronegativity it is apparent that metal ions (cations) that lose electron will therefore have lower electronegativity values than anions that gain electrons.
Thinking back to electronegativity it is apparent that metal ions (cations) that lose electron will therefore have lower electronegativity values than anions that gain electrons.
At this stage I will introduce another term: ionisation energy. This is the energy required to remove the outermost electrons from one mole of atoms in the gaseous state (see the separate post for further details on ionisation energy - aimed at Level 3).It should be apparent that cations that lose electrons will have a lower ionisation energy as well - it takes less energy to remove the electrons. The image below shows the trends in ionisation energy.
At this stage I will introduce another term: ionisation energy. This is the energy required to remove the outermost electrons from one mole of atoms in the gaseous state (see the separate post for further details on ionisation energy - aimed at Level 3).It should be apparent that cations that lose electrons will have a lower ionisation energy as well - it takes less energy to remove the electrons. The image below shows the trends in ionisation energy.
metallic bond
metallic bond
To complete the section on bonding the last type of bonding to cover is metallic bonding. Metallic bonding can be seen as an array of cations (metal atoms) surrounded by a sea of delocalised electrons. This determines the properties of metals. See this separate post on types of solids
To complete the section on bonding the last type of bonding to cover is metallic bonding. Metallic bonding can be seen as an array of cations (metal atoms) surrounded by a sea of delocalised electrons. This determines the properties of metals. See this separate post on types of solids
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