Topic 2 - Bonding and Structure Flashcards
What is an ion?
A positively or negatively charged atom (or group of atoms).
How are ions formed?
When electrons are transferred from one atom to another.
What are positive ions called?
Cations
What are negative ions called?
Anions
How do single atoms form ions?
They gain or lose 1, 2 or 3 electrons so that they have a full outer shell.
Is the charge on a metal ion positive or negative?
Positive
Is the charge on a non-metal ion positive or negative?
Negative
What is an ionic bond?
The strong electrostatic attraction between two oppositely charged ions.
What is the force responsible for ionic bonding?
Electrostatic attraction
What does the fomula of an ionic compound tell you?
The ratio of the ions in that compound.
How does the electrostatic attraction relate to the strength of an ionic bond?
The stronger the attraction, the strongere the bond.
What two factors affect the strength of an ionic bond?
- Ionic charges
* Ionic radius
How does ionic charge affect the strength of an ionic bond?
The greater the charge, the stronger the bond.
How does ionic radius affect the strength of an ionic bond and why?
- The smaller the radii, the stronger the bond.
* This is because smaller ions can pack more closely together and electrostatic attraction gets weaker with distance.
What is charge density of an ion?
The amount of charge per unit area or volume.
How does charge density affect the strength of an ionic bond?
Ions with high charge density form stronger bonds than those with low charge densities.
What is an ion with high charge density?
An ion with a large charge spread over a small area.
What is an ion with low charge density?
An ion with a small charge spread over a large area.
NaF and CaO.
Which has the higher melting point and why?
- CaO
- It is made up of Ca2+ and O2- ions, while NaF is made up of Na+ and F- ions.
- So the charges in the CaO are greater, resulting in stronger ionic bonds.
NaF and CsF.
Which has the higher melting point and why?
- NaF
- The ionic radius of Ca+ is greater than that of Na+.
- So Na+ and F- ions can pack more tightly than Ca+ and F- ions, resulting in stronger ionic bonds.
Describe how the size of an ion changes as you go down a group. Why?
It is increased, because extra electron shells are added.
What are isoelectronic ions?
Ions of different atoms with the same number of electrons.
Describe how the radius of isoelectronic ions changes as the atomic number increases.
It decreases, because there is greater attraction per electron from the protons, so they are pulled in closer.
What type of diagram is used to show ionic bonding?
Dot-and-cross diagrams