TOPIC 4: BONDING Flashcards
What is an ionic bond?
The electrostatic force of attraction between two oppositely charged ions
What elements form ionic bonds?
Metals and non-metals
What structure do ionic bonds take on?
They take on a three dimensional crystalline structure known as the lattice structure. Positively charged ions are packed as closely as possible to the negatively charged ions, whilst ions of the same charge are as far apart as possible. This maximises electrostatic attraction between the ions, while minimising repulsion.
- NaCl for example, has each sodium ion surrounded by 6 chloride ions and vice versa
What do ionic compounds have high melting points?
Due to the high strength of the electrostatic force of attraction between the ions
How are ionic bonds formed?
By atoms gaining or losing electrons
What is a polyatomic ion?
When more than one element forms a single ion
What are physical properties of ionic compounds?
- high melting and boiling points
- due to high electrostatic force of attraction
- low volatility (readiness to evaporate)
- conduct flow of electricity when melted
What is a covalent bond?
The attraction of two atoms to a shared (bonding) pair of electrons
What elements typically form covalent bonds?
Non-metals
How many bonds do atoms of different groups form?
Group 7 - 1 bond
Group 6 - 2 bonds
Group 5 - 3 bonds
What is the trend in bond strength?
As bond strength increases, length decreases, vice versa
What is a coordinate bond?
A shared pair of electrons where both electrons have originated from one atom
What is a polar bond?
When atoms in a covalent bond have differing electronegativities. The electron pair is displaced to the more electronegative atom due to higher attraction
What is the scale of bond tupes
Ionic bond = >1.8
non-polar covalent = <0.4
polar covalent = between 0.4 and 1.8
What is VSEPR?
Valence Shell Electron Repulsion Theory, based on the fact that each pair of electrons will be repelled from the others, causing them to move as far away as possible in 3-D space.
