Bonding, Structure and Energy Changes (Casey)

metallic bonding

metals are made up of metal atoms held together in a 3D lattice by metallic bonds, this is the strong attraction between positively charged nuclei of the atoms and the delocalised valence electrons

ionic bonding

ionic substances are made up of ions held together in a 3D lattice by ionic bonding, this is the strong attraction of positively charged cations and negatively charged anions

covalent bonding

strong attraction between two positive nuclei and one or more shared pairs of electrons

covalent networks

covalent network solids are made up of atoms held together in a 3D or 2D lattice by covalent bonding, this is the strong attraction between positive nuclei and shared electrons

covalent molecules

molecular substances are made up of discrete neutral molecules with weak intermolecular forces

melting and boiling

melting requires supplying enough energy to disrupt/break the bonds between the particles in the substance

melting and boiling - metallic

melting requires supplying enough energy to disrupt/break the bonds between the particles in the substance, metals are made up of a 3D lattice of metal atoms surrounded by a sea of delocalised valence electrons which are strongly attracted to the nuclei in the lattice, this forms a strong metallic bond which requires a large amount of energy to break, therefore the melting point is high

melting and boiling - ionic

melting requires supplying enough energy to disrupt/break the bonds between the particles in the substance, ionic compounds are made up of a 3D lattice with strong ionic bonds between cations and anions, these bonds require a large amount of energy to break, therefore the melting point is high

melting and boiling - covalent network

melting requires supplying enough energy to disrupt/break the bonds between the particles in the substance, covalent networks are made up of atoms held in a 3D or 2D lattice by strong covalent bonds, these bonds require a large amount of energy to break, therefore the melting point is high

melting and boiling - covalent molecular

melting requires supplying enough energy to disrupt/break the bonds between the particles in the substance, molecular substances are made up of discrete neutral molecules with weak intermolecular forces between the molecules, because the forces are weak they require a small amount of energy to separate the molecules, therefore the melting point is low

electrical conductivity

electrical conductivity requires a substance to have mobile charged particles (ions or electrons)

electrical conductivity - metallic

electrical conductivity requires a substance to have mobile charged particles, metals are made up of a 3D lattice of metal atoms surrounded by a sea of delocalised valence electrons, these valence electrons are free to move throughout the structure, therefore the metal can conduct electricity

electrical conductivity - ionic

electrical conductivity requires a substance to have mobile charged particles, ionic substances are made up of a 3D lattice of cations and anions that are attracted to each other, in the solid state these ions are rigidly held in a lattice by strong ionic bonds so cannot move around and therefore cannot conduct, when molten and in solution the ions are able to move freely so they can conduct

electrical conductivity - covalent networks (diamond and SiO2)

electrical conductivity requires a substance to have mobile charged particles, covalent networks are made of atoms held together in a 3D lattice by strong covalent bonds, all of the valence electrons for each atom form the maximum number of covalent bonds, therefore there are no delocalised electrons free to move, so they cannot conduct

electrical conductivity - covalent networks (graphite)

electrical conductivity requires a substance to have mobile charged particles, covalent networks are made up of a 2D lattice by strong covalent bonding, in graphite each carbon is bonded to 3 other carbon atoms, this leaves one delocalised valence electron from each carbon atom, these electrons are free to move, so they can conduct electricity

electrical conductivity - covalent molecular

electrical conductivity requires a substance to have mobile charged particles, molecular substances are made up of discrete neutral molecules, because they are neutral they have no mobile charged particles, therefore they cannot conduct electricity

malleability/ductility and hardness

malleability requires the substance to have non-directional forces of attraction so the particles can move when a force is applied

malleability/ductility and hardness - metallic

malleability requires the substance to have non-directional forces of attraction so the particles can move when a force is applied, metals are made up of metal atoms held in a 3D lattice surrounded by a sea of delocalise valence electrons by non-directional metallic bonds, the metallic bonds are non-directional as the electrons are delocalised across the lattice, when a force is applied, the atoms can move without disrupting these bonds thus the structure can change shape without breaking the lattice

malleability/ductility and hardness - ionic

malleability requires the substance to have non-directional forces of attraction so the particles can move when a force is applied, ionic substances are made up of a 3D lattice of cations and anions directly bonded to one another with ionic bonds, ionic substances are not malleable or ductile because if a force is applied to an ionic lattice, it forces ions with the same charge next to each other; which repel and the lattice structure breaks, therefore these substances are brittle

malleability/ductility and hardness - covalent network

malleability requires the substance to have non-directional forces of attraction so the particles can move when a force is applied, covalent networks are not malleable because if a force is applies, the directional strong covalent bonds have to be broken before the atoms can move, this would result in the breaking of the lattice

malleability/ductility and hardness - covalent molecules

malleability requires the substance to have non-directional forces of attraction so the particles can move when a force is applied, covalent molecules are not malleable because the weak intermolecular forces holding the solid together will easily break when a force is applied

solubility in water

dissolving requires the attraction for the polar water molecules to be greater than the forces holding the solid together

solubility in water - metallic

dissolving requires the attraction for the polar water molecules to be greater than the forces holding the solid together, metals are made of a 3D lattice of metal atoms surrounded by a sea of delocalised valence electrons, there is no attraction between the metal atoms and the polar water molecules, therefore metals are insoluble in water

solubility in water - ionic

dissolving requires the attraction for the polar water molecules to be greater than the forces holding the solid together, when an ionic solid dissolves in water, it separates into its ions, the ions are charged and attracted to the charged ends of the polar water molecule, the slightly negative charges on the oxygen ends of the water molecules are attracted to the positive ion, and the slightly positive hydrogen ends of the water molecules are attracted to the negative ions, this causes the ions to be surrounded by water molecules and the lattice breaks down, the solid is soluble because the force of attraction between the ions and water is strong enough to overcome the forces holding the ions together along with the forces holding the water molecules together

solubility in water - covalent network

dissolving requires the attraction for the polar water molecules to be greater than the forces holding the solid together, covalent networks are made up of atoms held together in a 3D or 2D lattice by strong covalent bonding, the interaction between the polar water molecules and the atoms is not strong enough to attract the atoms out of the lattice, therefore covalent networks are insoluble in water

solubility in water - covalent molecular polar

dissolving requires the attraction for the polar water molecules to be greater than the forces holding the solid together, polar molecules will dissolve in water, because the slightly negative oxygen end of the polar water molecule attracts to the slightly positive end of the polar molecule, and the slightly positive hydrogen end attracts the slightly negative end of the polar molecules which allows them to mix

solubility in water - covalent molecular non-polar

dissolving requires the attraction for the polar water molecules to be greater than the forces holding the solid together, non-polar molecules will not dissolve in water, the slightly negative oxygen and slightly positive hydrogen ends of the polar water molecules attracts adjacent water molecules, because the non-polar molecules had no slightly positive or negative end it does not attract with the polar water molecules preventing them from mixing

valence electron repulsion

the shape and angle are controlled by minimising repulsion of the electron areas around the central … atom, the electron arrangement that minimises repulsion for … electron ares is … which results in an angle of …, because … electron areas are bonding and … are non-bonding, it results in a … shape with a bond angle of …

electronegativity

the ability of an atom to attract the bonding pair of electrons in a covalent bond

polarity code

molecular polarity is controlled by the distribution of charge about the central … atom, the … bonds are polar because … are more electronegative than …, this results in uneven sharing of electrons which forms bond dipoles, this molecule has a … shape, which is symmetric/asymmetric, as the bond dipoles are all the same/different they will cancel/not cancel and the molecule will be non-polar/polar

enthalpy

a thermodynamic quantity equivalent to the total heat content of a system

endothermic

• bonds break

• requires energy

• temp of surroundings decreases

• change in enthalpy is positive

• products have more enthalpy than the reactants

exothermic

• bonds from

• releases energy

• temp of surroundings increases

• change in enthalpy is negative

• reactants have more enthalpy than products

bond energies

• the energy required to break one mole of bonds when the substance is in the gaseous state

• energy is always absorbed when bonds are broken and released when bonds are formed (bond energies are average values)