An ionic bond is an attraction between oppositely charged ions which are formed by the transfer of electrons from one atom to another
A covalent bond is a pair of electrons shared between two atoms
A dative covalent bond is a pair of electrons shared between two atoms, one of which provides both electrons to the bond
A dative covalent bond is represented by a short arrow from the electron pair providing atom to the atom providing neither
A metallic bond is an attraction between cations and a sea of electrons
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Ionic Or Covalent? (Electronegativity)
Electronegativity is the relative ability of an atom to attract electrons in a covalent bond
Electronegativity increases across a period as the nuclear charge on the atoms increase but the shielding stays the same
Electronegativity decreases down a group as the number of shells increase, therefore so does the shielding
An atom with high electronegativity is electronegative
An atom without high electronegativity is electropositive
If both atoms have electronegativities less than 1.9 then the bond is metallic
If either atom has an electronegativity greater than 1.9 and the difference is less than 0.5 then the bond is covalent
If the difference is more than 0.5 but less than 2.1 then the bond is polar covalent
If the difference is greater than 2.1 then the bond is ionic
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Ionic Structures
Ions in ionic bonds come together to form a lattice
In a lattice all the anions are surrounded by cations and vice versa
The attraction between opposite ions is very strong, making the boiling/melting point of ionic compounds very high
The higher the charge on the ions, and the smaller they are, the stronger the attraction
Ionic lattices cannot conduct electricity when solid as the ions are locked in place
Ionic lattices can conduct electricity when liquid as the ions are free to move
Ionic lattices are hard and brittle as ions cannot move or slip over eachother easily
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Metallic Structures
Metallic bonding is the attraction between cations and a sea of delocalised electrons
The cations are arranged in a lattice with the electrons free to move between them
The melting/boiling point of metallic structures is generally lower than ionic structures, whilst still being high
Smaller ions, and those with a high charge, attract electrons more strongly and therefore have higher melting/boiling points
The metal cations slide over eachother and therefore metallic structures are soft, malleable, and ductile
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Intermolecular Forces
There are 3 types of intermolecular forces
Van der Waal's forces
Caused when electrons move to one side of a molecule more than another (temporary dipole), which then causes an induced dipole in an adjacent molecule
Can be found in every molecule - weakest intermolecular force
The more electrons in the molecule, the greater the likelihood of a temporary dipole forming
The larger the surface area of the molecule, the more contact it will have with adjacent molecules, therefore the greater the chance of a dipole being induced
Permanent dipole
Found in polar molecules
Stronger than van der waal's forces
Hydrogen bonding
Found when hydrogen has a direct bond with Nitrogen, Oxygen, or Fluorine (NOF)
Strongest intermolecular force
Due to hydrogen being electropositive and NOF being very electronegative
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