Chemistry: Notes on Bonds
Topic 4 - Bonding
4.1 Ionic bonds
4.1.1
Ionic bond: +ve (cations) and -ve (anions) ions are attracted to each other and form a continuous ionic lattice
4.1.2
Group 1 metals form +1 ions, group 2 metals form +2 ions, metals in group 3 form +3 ions .
Examples : Li+, Mg2+, Al3+. Greater ease of ionisation Li->Cs is due to the increased electron shielding of the nuclear attraction caused by additional inner shells of electrons. The easier atoms are to ionise, the more reactive they will be because less energy is required to ionise them, and so they react faster.
4.1.3
Group 5 will form 3- ions, Group 6 ions will form 2- ions, Group 7 ions will form negative ions. Examples : O2-, Cl-.
4.1.4
The transitions metals (elements from Ti to Cu, ignoring Sc and Zn) can form multiple ions (i.e. Fe2+, Fe3+) due to proximity of 4s and 3d shells.
4.1.5
The ionic or covalent nature of the bonding in a binary compound is a result in the difference between their electronegativity. NaCl(s) is ionic, HCl(g) is (polar) covalent (note: covalent molecules tend to be gases/liquids, ionic tends to be solid, although network covalent would be solid). In general, if the difference between electronegativities is greater than 1.7, the bond will be more than 50% ionic.
4.1.6
Take the name of the group 1,2, or 3 metal and add ‘fluoride’, ‘chloride’, ‘bromide’, ‘iodide’ etc , ‘oxide’, ‘sulfide’ etc. or even nitride or phosphide.
4.2 Covalent bond
4.2.1
Covalent bonds are where two atoms each donate 1 electron to form a pair held between the two atoms. Such bonds are generally formed by atoms with little difference in electronegativity, i.e. C, H and O in organic chemistry.
4.2.2
All electrons must be paired.In Lewis diagram, the outermost(valence)shell eletrons are represented by dots or crossess. In general C forms 4 bonds, N forms 3, O forms 2, halogens form 1, H forms 1. (Li would form 1, Be 2, and B 3 but they don’t usually, preferring
4.1 Ionic bonds
4.1.1
Ionic bond: +ve (cations) and -ve (anions) ions are attracted to each other and form a continuous ionic lattice
4.1.2
Group 1 metals form +1 ions, group 2 metals form +2 ions, metals in group 3 form +3 ions .
Examples : Li+, Mg2+, Al3+. Greater ease of ionisation Li->Cs is due to the increased electron shielding of the nuclear attraction caused by additional inner shells of electrons. The easier atoms are to ionise, the more reactive they will be because less energy is required to ionise them, and so they react faster.
4.1.3
Group 5 will form 3- ions, Group 6 ions will form 2- ions, Group 7 ions will form negative ions. Examples : O2-, Cl-.
4.1.4
The transitions metals (elements from Ti to Cu, ignoring Sc and Zn) can form multiple ions (i.e. Fe2+, Fe3+) due to proximity of 4s and 3d shells.
4.1.5
The ionic or covalent nature of the bonding in a binary compound is a result in the difference between their electronegativity. NaCl(s) is ionic, HCl(g) is (polar) covalent (note: covalent molecules tend to be gases/liquids, ionic tends to be solid, although network covalent would be solid). In general, if the difference between electronegativities is greater than 1.7, the bond will be more than 50% ionic.
4.1.6
Take the name of the group 1,2, or 3 metal and add ‘fluoride’, ‘chloride’, ‘bromide’, ‘iodide’ etc , ‘oxide’, ‘sulfide’ etc. or even nitride or phosphide.
4.2 Covalent bond
4.2.1
Covalent bonds are where two atoms each donate 1 electron to form a pair held between the two atoms. Such bonds are generally formed by atoms with little difference in electronegativity, i.e. C, H and O in organic chemistry.
4.2.2
All electrons must be paired.In Lewis diagram, the outermost(valence)shell eletrons are represented by dots or crossess. In general C forms 4 bonds, N forms 3, O forms 2, halogens form 1, H forms 1. (Li would form 1, Be 2, and B 3 but they don’t usually, preferring