El 7 Flashcards
What is ionic bonding?
Ionic bonding is the complete transfer of valence electron(s) between atoms and is a type of chemical bond that generates two oppositely charged ions.
How are ions formed?
When electrons are transferred from from one atom to another atom to gain the nearest noble gas electronic configuration
What do metals form when they lose electrons?
Positive cations, they are therefore smaller than the original atom.
What do non-metals form when they gain electrons?
negative anions, they are therefore larger than the original atom because of the electron repulsion in the outer shell
What is the energy associated with removing the electrons?
First ionisation energy
Why is energy released when a non metal atom becomes a negatively charged anion?
Energy is released as the nucleus pulls in an electron this energy that is released is called electron affinity
What is electron affinity?
Electron affinity is the change in energy of a neutral atom when an electron is added to the atom to form a negative ion (the neutral atoms likelihood of gaining an electron)
What is the general trend of the charge on a metal ion?
Its charge is equal to its group number
What is the general trend of the charge on a non-metal ion?
Its charge is equal to its group number minus 8
How are oppositely charged ions held together?
They are held together by their opposite charges in an electrostatic bond and the oppositely charged ions attract each other strongly (When ions are held together like this, its called ionic bonding)
What is a complex ion?
Complex ions are ions that contain more than one type of atom, the whole ion group carries an electrical charge (the electrical charge is spread across the whole group)
What is the structure of an ionic compound?
Ionic compounds contain oppositely charged ions that are held together in a giant lattice structure.
How does a lattice stay together?
Within the lattice, the ions with different charged attract each other and the ions with the same charge repel each other. The ions arrange themselves to maximise the attractions and minimise the repulsions.
What is the overall attraction in a lattice structure called?
Ionic bonding
What are ionic crystals?
Ionic crystals are giant lattices of ions, a lattice is just a regular structure
What state are ionic substances at room temperature and pressure (typically)
Solids
How is the lattice structure arranged?
The lattice structure consists of repeating positive and negative ions in all 3 dimensions, because of this, ionic compounds often form regularly shaped crystals
When do ionic compounds conduct electricity?
When molten or dissolved in a solution
Do ionic compounds have high or low melting points?
High melting points
Are ionic compounds typically soluble or insoluble?
Soluble
Why do ionic substances only conduct electricity when molten or dissolved - but not when they’re solid?
Ions in a liquid or a solution can move around freely and take their electrical charges with them. Ionic compounds conduct electricity when dissolved in water, because the dissociated ions can carry charge through the solution.
Why do ionic compounds have high melting points?
The ions in a giant lattice are held together by strong electrostatic forces of attractions between each individual ion. A large amount of energy is required to overcome theses forces so their melting points are high.
Why are most ionic compounds soluble?
Ionic compounds dissolve readily in water because water molecules are polar (one end is slightly positive and one end is slightly negative). The ions in the compound also have a small negative or positive charge and therefore, the water molecules can attract the ions and pull the ions away from the lattice. The ions become surrounded by water molecules and spread out evenly throughout the solution, once the ions are separate they behave independently of each other (can undergo separate reactions).
What ionic compounds are insoluble?
Barium, lead and silver sulphates
Silver and lead halides
All metal carbonates
Metal hydroxides except group 1 hydroxides and ammonium hydroxide
What are spectator ions?
Ions that aren’t included in the reaction so can be left out of the ionic equation
Why might an ion be a spectator ion?
For example in a solution a positive ion may react and leave the negative ion unchanged, this means that the negative ion is a spectator ion and can be dismissed from the ionic equation
How is a molecule formed?
When two or more atoms bond together via a covalent bond in order to gain a full outer shell of electrons. Both positive nuclei are electrostatically attracted to the shared electrons
Why do atoms want a full outer shell of electrons?
Because atoms with a full outer shell of electrons are extremely stable and inert
As well as an electrostatic attraction between the nuclei and the electrons what is there?
There is also a repulsion between the positive nuclei
How is a covalent bond maintained?
To maintain the covalent bond, there has to be a balance between the electrostatic attraction and the repulsion.
Do molecular substances have high or low melting and boiling points? Why?
Low melting and boiling points. This is because there is no giant structure that has to be broken down
Do molecular substances conduct electricity? Why?
They do not conduct electricity because there are no charge carriers that are free to move. Molecular compounds also don’t dissociate into ions and so don’t conduct electricity in solution
Are molecular substances soluble or insoluble? Why?
Molecular substances are typically insoluble in water because the water molecules are more attracted to each other than the molecular substance
What is a dative covalent bond?
In a covalent dative bond, one atoms donates both electrons to a bond (the electrons come from one atom)
How is a covalent dative bond shown?
A covalent dative bond is shown by an arrow, the arrow points away from the atom that donates the pair of electrons.
How are giant covalent substances formed?
GCS are formed via covalent bonds, covalent bonding usually results in simple molecular covalent substances but it can also produce huge great lattices too - that contain billions and billions of atoms (Giant molecular covalent substance).
What is covalent bonding like in giant covalent substances?
There is a huge network of covalent bonds, and the electrostatic attractions holding individual covalent molecules together is much stronger (high intermolecular forces of attraction)
Give an example of a Giant covalent substance
Diamond and Graphite
Why do GMCS have high melting points?
Because a lot of energy is required to be able to break the very strong intermolecular bonds within a GMCS before it melts
Why are GMCS’ typically hard?
Because there are very strong bonds within the lattice arrangement
Why are GMCS’ good thermal conductors?
Because vibrations can travel easily through the stiff lattices
Why are GMCS’ insoluble?
They are insoluble because the covalent bonds means that the atoms are more attracted to their neighbouring molecules in the lattice than to the solvent molecules.
Why are GMCS’ typically not able to conduct electricity?
Because there are no charged ions/electrons that are free to move throughout the substance
Give one example of a GMCS that can conduct electricity and why it can conduct electricity
Graphite can conduct electricity and is very soft. Graphite can be used for a lubricant because there are weak forces between the layers in its structure so they can slide over each other easily. It can conduct electricity because their is one electron in every carbon atom that can move between the layers & can therefore be used to make electrodes.
What does the fact that GMCS’ are insoluble in solvents say about them?
They don’t contain any ions otherwise they could be dissolved in the solution.
Describe the structure of a metal
Metals exist as giant metallic lattice structures - the electrons in the outermost shell of the metal atom are delocalised ad are free to move about throughout the structure (positive metal ion). The positive metal ions are surrounded by a sea of delocalised valance electrons that are free to move.
Why do metals conduct electricity?
Metals conduct electricity because the delocalised sea of electrons are free to move and can carry their charge with them.
Why are metals insoluble?
With regard to insoluble metals the attraction between the metal cations and the delocalised electrons in the lattice is greater then the attraction between the metal cations and the water molecules and as a result the metal is insoluble.
Are metals hard or soft at room temperature?
Metals are hard but malleable (with the exception of mercury). This is because of the strong metallic bonding between the positive cations and delocalised electrons
Do metals have high or low melting and boiling points?
Metals have high melting and boiling points (except mercury), this is because there are strong metallic bonds between the positive cations and negative delocalised electrons within the lattice structure meaning a large amount of energy is required to over come these strong bonds.
