ionic bonding and structure Flashcards
what is an ionic bond?
electrostatic attraction between electric charges of a cation and an anion. This force is non-directional (it acts in all directions).
the strength of this force depends on (a) the magnitude of the charges of the ions and (b) the sum of the ionic radii of the ions
what is electrostatic attraction
When a negatively charged atom is attracted towards positively charged atom and vice-versa
how are ionic bonds formed
one or more electrons is transferred from one atom to another through oxidation and reduction.
e.g. Na can be Na+ and oxidized to form the noble gas configuration of Ne. Cl can be reduced to Cl- and the noble gas configuration of Ar.
Therefore, the electron lost by Na is gained by Cl. This forms the ionic compound, NaCl
what is the result of an ionic bond
the driving force of this bonding is to attain more stable, noble gas electronic configuration for both of the atoms involved.
What are the characteristics for how ionic bonds form
Typically between metals and nonmetals.
The strict definition, however involves electrostatic charge between two ions of opposite charge
How do you determine whether a compound is ionic or covalent?
The difference in electronegativities: as the difference increases, the bond becomes more ionic.
Bond identity is continuous: bond type changes gradually from pure ionic to pure covalent, passing through all degrees
how is the purest ionic compound formed?
when group 1 metals combine with nonmetals. these metals are highly electropositive (electronegativity values between 0.7 to 1.0)
what is the structure of an ionic compound?
In normal conditions, ionic compounds are typically solid with a lattice-type structure: consisting of 3D repeating units of cations and anions
What is a lattice structure
structures that consist of three-dimensional repeating units
of positive and negative ions
what is the octet rule?
In order to achieve a noble gas core electron configuration, elements tend to lose electrons (oxidations), gain electrons (reduction), or share electrons
This rule dictates that atoms are most stable when their valence shells are filled with eight electrons.
when is the octet rule not obeyed?
NO and NO2
What are the physical properties of ionic compounds?
- they have high melting and boiling points. This is because of the strong electrostatic forces of attraction between the ions in their lattice structures
- Volatility: This is the tendency of a substance to vaporize. Ionic compounds have low volatility due to the strength of their electrostatic forces.
Electrical conductivity
When in a solid state, ions cannot move , so solid ionic compounds do not conduct electricity
when in a molten state, ions can move and therefore conduct electricity
Solubility
ionic compounds dissolve in polar solvents (e.g. water) but not non-polar solvents
