Covalent bonding (Chapter 8) Flashcards
What is covalent bond?
In a covalent bond, a pair of electrons is shared between two atoms.
What is covalent bond held by?
It is held by strong electrostatic attraction between the nuclei of the atom and the shared pair of electrons.
What is diatomic atoms?
Diatomic molecules contain 2 atoms.
What do we call atoms which have same number of electrons in their outer shells as a noble gas atom?
Isoelectronic of the noble gas atom.
What happen when atom can form more bonds?
The more bonds atom can form, the more energy is release and the more stable the system becomes.
The lower the energy molecule has, —— it become.
The more stable
Why molecules with more bonds are more stable?
When more bonds form, more energy is released making the result substance to have lower energy, making it more stable.
Pair of electrons in the outer shell of the central atom _____ each other.
repel
What is double and triple covalent bond?
Double covalent bond - molecules that have 2 shared pairs of electrons between atoms
Triple covalent bond - molecules that have 3 share pairs of electrons between atoms
What is intermolecular force?
Force of attraction between same molecules which hold them together.
Which is weaker, intermolecular force between molecules or covalent bonds?
Intermolecular force between molecule.
What is simple molecular structure?
Substance that consists of molecules with intermolecular force of attraction between them.
Which states does substances with simple molecular structure tend to stay?
Gas or liquid
Why substances with simple molecular structure have low melting and boiling point?
Because not much energy is required to break the weak intermolecular force of attraction between molecules.
The relative molecular increase, their melting point and boiling point —–.
Increase
The more relative molecular, the —– the intermolecular attraction between molecules.
stronger
What are physical properties of covalent compounds?
- They don’t conduct electricity
- They tend to be insoluble in water
- They are often soluble in covalent compounds
Why covalent molecules do not conduct electricity?
Because the molecules don’t have any overall electrical charge and all electrons are held tightly in the atoms or in covalent bonds.
Why diamond has high melting and boiling point?
Because of the very strong carbon-carbon covalent bonds, which extend throughout the whole crystal in three dimensions.
Why does diamond not have no intermolecular force?
Because it has giant structure, so, it has no molecules.
Which state does substances with giant covalent structure tend to stay?
Solid
What are some examples of giant covalent structures?
Diamond, graphite, silicon dioxide
Does diamond conduct electricity?
No, because all the electrons in the outer shells of carbon atoms are tightly held in covalent bonds between the atoms.
Diamond can conduct heat very well.
True
What kind of structure does graphite have?
Giant structure composed in layers
Where are graphite used?
In pencils
Graphite has _____ melting and boiling point.
High
Why does graphite conduct electricity?
Because each carbon atoms forms three covalent bonds sharing three electrons and the remaining fourth one is free to move around throughout the whole layer.
What are delocalized electrons?
The electrons that are free to move throughout the layers.
What are the allotropes of carbon?
Diamond, graphite and fullerene
What are allotropes?
Allotropes are different forms of the same element.
What are properties of fullerene?
- It has lower melting and boiling point than diamond and graphite
- It is not as hard as diamond
- It doesn’t conduct electricity
- It can dissolve in some solvent
Why fullerene does not conduct electricity?
Although all carbon atoms of fullerene forms three bonds, the fourth electron on each atom can only move around within each fullerene molecule.
What are properties of graphite?
- It has high melting point and boiling point
- It conducts electricity
- It is insoluble in all solvents
- It is less dense than diamonds
Which kind of structure does fullerene have?
Simple molecular structure
