1.3 Bonding Part 2 Flashcards
Define electronegativity
The power of an atom to attract the pair of electrons in a covalent bond
What happens to electronegativity value across a period? Why?
Increases because there is a smaller distance and a higher nuclear charge
What happens to the electronegativity value down a group? Why?
Decreases because the bonded electrons are further from the nucleus and have more shielding
What is the most electronegative atom?
Fluorine
Why do noble gases not have electronegativity values?
They don’t normally form covalent bonds
Is the molecule C-F polar? If yes show the partial charges
Yes
C - delta positive
F - delta negative
Is the molecule C-H polar? If yes show the partial charges
No
Is the molecule N-H polar? If yes show the partial charges
Yes
N - delta negative
H - delta positive
Is the molecule O-H polar? If yes show the partial charges
Yes
O - delta negative
H - delta positive
Is CO2 polar?
- It has polar bonds
- Non-polar molecule
- molecule is symmetrical so the dipoles cancel
Is H2O polar?
Yes
Polar bonds
Polar molecule
What are the three types of intermolecular force?
- Van Der Waals
- Permanent dipole-dipole
- Hydrogen bonds
What causes Van Der Waals forces?
The movement of electrons which unbalanced the charge distribution within the molecule
What is a Van Der Waals force and how does it form?
- electrons move which unbalanced the charge distribution
- This creates an instantaneous dipole across the molecule
- This induces a dipole in neighbouring molecules
- Resulting in weak forces of attraction
Do bigger molecules have greater or weaker Van Der Waals forces?
Stronger
More electrons
Draw and describe the intermolecular force formed from two HCl molecules joining
Permanent dipole-dipole
H - delta pos
Cl - delta neg
Hydrogen joins with chlorine
Between what does hydrogen bonding occur?
N-H
O-H
F-H
What happens when a gas turns into a solid?
Deposition
What happens when a solid turns into a gas?
Sublimation
When can an electric current flow?
When charged particles are free to move
What can carry a current?
Delocalised electrons or free ions
What can ionic and polar substances dissolve in?
Polar solvents
What can non polar substances dissolve in?
Non polar solvents
What is a giant ionic lattice belt together by?
The electrostatic attraction between the oppositely charged ions
Why do ionic compounds have high melting points?
The ions are held together by strong ionic bonds which need a lot of energy to break
Do ionic compounds conduct electricity when solid with reason
No
The ions are not free to move so cannot carry the current
Do ionic compounds conduct electricity when dissolved or molten with reason
Yes
The ions are free to move so can carry the current
Why are ionic compounds brittle?
- If enough force is applied the layers slide over each other
- Like charges will move next to each other, causing repulsion and the lattice structure breaks down
Why do metals have high melting points?
Metallic bonds are strong, so a large amount of energy is needed to break them
Why do metals conduct electricity?
Because the delocalised electrons can flow through the structure and carry the current
Why are metals strong?
- Metallic bonds are strong and extend through the giant metallic lattice
- Metallic bond strength depends on the size and charge of the metal ion
Why are metals malleable and ductile?
The layers of ions in the giant ionic lattice can slide over each other into new positions, without disrupting the metallic bond
What are the two types of covalent substance?
- Simple molecular covalent
* Macromolecular covalent
Why do covalent substances have low melting points?
The forces of attraction between the molecules are weak
Not much energy is needed to break them
Are covalent substances soluble?
Generally insoluble in water, unless they can form hydrogen bonds or react with water
Can covalent substances conduct electricity?
No
They don’t contain ions or delocalised electrons
