covalent bonding Flashcards
Covalent compounds are formed when
pairs of electrons are shared between atoms
only __________ elements participate in covalent bonding
non metal
just like un ionic bonds, each atom has a ___ outer shell of electrons
full
Covalently bonded substances may consist of __ molecules or ___ molecules
small
giant
a single covalent bond is
when two adjacent atoms share one pair of electrons
( like hydrogen)( H-H)
If two adjacent atoms share two pairs of electrons, two covalent bonds are formed, also known as a
Double bond
Some atoms need to share more than one pair of electrons to gain a full outer shell of electrons
true or false
true
Properties of simple molecular compounds
They have low melting and boiling points so covalent compounds are usually liquids or gases at room temperature
As the molecules increase in size, the melting and boiling points generally increase
Small molecules have poor electrical conductivity
They have low melting and boiling points as there are
only weak intermolecular forces acting between the molecules
why are they gases or liquids at room temp
the forces are very weak when compared to the covalent bonds
why does melting point increase, when size increase
As the molecules increase in size the intermolecular forces also increase as there are more electrons available
This causes the melting and boiling points to increase
why are they poor conductors
there are no free ions or electrons to carry the charge.
are covalent compounds conductors or insulators
insulators
simple molecular structures have low melting & boiling points bevause
There are weak intermolecular forces between the molecules
These forces require little energy to overcome
Most simple molecular structures are either ____ or ___ at room temperature
gases or liquids
giant covalent structures are ___ with ___ melting and boiling points
solids
high
they have a ___ _____ structure
giant lattice
All giant covalent structures have high melting points because:
There are strong covalent bonds between atoms
These require lots of energy to overcome
diamond and graphite contain only ____ atoms
carbon
in diamond, each carbon atom bonds with ___ other carbons forming a ___-
4
tetrahedron
diamond is very hard because : (3)
Each carbon atom is covalently bonded to four other carbon atoms
The covalent bonds are very strong
The hardness of diamond makes it useful for cutting tools
diamond has a high melting point because (2):
It has a giant covalent structure
There are strong covalent bonds between atoms which need lots of energy to break
in graphite, each carbon atom is bonded to __ others
3
in graphite there are ___ electrons
free, delocalised
properties of graphite (4)
soft
slippery
high melting point
conduct electricity and heat (electrons can move between the layers in graphite)
why can graphite conduct electricity and heat
because there are delocalised electrons as carbon atoms only form 3 bonds, the delocalised electrons are free to move
why does graphite have a high melting and boiling point
this is because each carbon atom forms 3 other strong bonds which need a lot of energy to break.
Because it has a giant covalent structure
