Topic 4: Chemical bonding and structure Flashcards
What is an ionic compound?
The electrostatic attraction between oppositely charged ions
What is an ion?
A charged species that is formed when electrons are transferred from one atom to another
What is the structure of ionic compounds?
Lattice
The octet rule
Elements tend to lose or gain electrons or share electrons in order to acquire a noble gas configuration
Electrical conductivity of ionic impounds
It cannot conduct electricity in the solid state, but it can conduct electricity when molten or in an aqueous solution
Solubility of ionic compounds
Soluble in polar solvents (eg: water) but not non polar solvents. Ions are attracted to ester molecules and are pulled away from the lattice and the separate ions are hydrated by water molecules
Volatility meaning
The tendency of a substance to vaporise
Volatility of ionic compounds
Ionic compounds have a strong electrostatic force of attraction between oppositely charged ions, making the volatility low
Why are ionic compounds not soluble in non-polar solvents?
There is no attraction between the non-polar solvent and the ions of the lattice
Brittleness of ionic compounds, why?
Ionic compounds shatter when they are hit, because when they are suddenly hit with a force, the ions shift, so that like charges become situated next to each other, and they repel each other so the lattice structure breaks apart
Electronegativity definition
The power of an atom in a molecule to attract electrons to itself
Electronegativity trend
Lowest in in lower left and highest in upper right
Ionic compounds is usually between a
A metal + a non-metal
Covalent compounds is usually between two
Non-metals
Ionic compounds Electronegativity difference
More than 1.8
Covalent compounds Electronegativity difference
Equal to or less than 1.8
Polar covalent compounds Electronegativity difference
Between 0 and 1.8 (non inclusive)
Metals ions charge
Usually Positive
Non-metals charge
Usually negative
Atoms that are stable with less than 8 electrons in the valence shell
Hydrogen, boron, beryllium
Suffix for anions in an ionic compound, give an example
-ide (eg:chloride)
Oxoanions meaning
Polyatomic ions containing oxygen (eg: NO3 -)
Why is NaCl described as having a local octahedral geometry?
Each sodium ion is surrounded by six chloride ions and each chloride ion is surrounded by six sodium ions
Formula for lithium
Li +
Formula for sodium
Na +
Formula for potassium
K +
Formula for caesium
Cs +
Formula for Calcium
Ca 2+
Formula for Magnesium
Mg 2+
Formula for aluminium
Al 3+
Formula for zinc ion
Zn 2+
Formula for copper (II)
Cu 2+
Formula for lead
Pb 2+
Formula for iron (II)
Fe 2+
Formula for iron (III)
Fe 3+
Formula for fluoride
F -
Formula for chloride
Cl -
Sulfide
S 2-
Formula for bromide
Br -
Formula for iodide
I -
Formula for oxide
O 2-
Nitride
N 3-
What has both covalent bonding and ionic bonding?
An ionic compound containing polyatomic ions
Phosphide
P 3-
What are polyatomic ions?
Ions that consist of more than one atom
Formula of ammonia
NH3
Formula of hydroxide
OH -
Formula of amonium
NH4 +
Formula of nitrite
NO2 -
Formula of nitrate
NO3 -
Formula of hydrogen carbonate
HCO3 -
Formula of sulphate
SO4 2-
Formula of carbonate
CO3 2-
Sulfite
SO3 2-
Formula for phosphate
PO4 3-
Formula for chlorite
ClO2 -
Formula for perchlorate
ClO4 -
Formula for chlorate
ClO3 -
Formula for hypochlorite
ClO -
The melting and boiling points of ionic compounds–why?
Relatively high, because of the strong forces of attraction between ions in a lattice structure
Volatility
How easy a substance vaporizes (boiling point)
What is hydration?
When seperated ions are surrounded by water molecules
Examples of non-polar solvents
Hexane, propane
Do ionic compounds conduct electricity? Why/why not?
They do not in solid form because ions are held in fixed positions in the lattice structure. When an ionic compound is dissolved/molten, ions are free to move and carry an electric current
Why do ionic compounds shatter when force is applied?
When a force is applied, the ions move and the force of repulsion between of the same charge causes the lattice structure to split and fracture.
Why can some ionic compounds dissolve in water?
The partial charges of water molecules are attracted to the oppositely charged ions in the lattice structure. The ions break off and are surrounded by water molecules. If the forces between the ions and water molecules are stronger than the attraction between the ions themselves, then the ionic compound is soluble.
Define covalent bonding
The electrostatic attraction between positively charged nuclei and shared pairs of bonding electrons
Why are longer bonds weaker than shorter bonds?
Because of the increased distance between the nuclei and the shared pairs of electrons, which results in a weaker electrostatic attraction between the atoms
Why are multiple bonds stronger than a single bond?
Multiple bonds involve more shared electrons between the atoms, so the electrostatic attraction is greater
How do you know if a covalent bond is a coordinate covalent bond?
If the bonding electrons come from one atom (in a regular covalent bond, electrons come from both atoms)
Example of a coordinate covalent bond?
CO (carbon monoxide)
NH4 + (Ammonium ion)
H3O + (Hydronium ion)
Aluminium chloride is a bond between a metal and non-metal–why is it not an ionic bond?
Aluminium chloride is electron deficient, it still needs two electrons to complete the octet in the outer shell of the aluminium atom, which creates a polar covalent bond
What is a dimer?
A larger molecule formed composed of two smaller, identical molecules and can be linked by coordinate covalent bonds or hydrogen bonds
