Covalent Bonds Flashcards
What are covalent bonds?
Why do atoms do this?
Strong bonds where atoms share electrons to form a full outer shell.
So that they feel like they have a full outer shell and are stable like a noble gas.
Each covalent bond provides what for each atom involved?
So a covalent bond is a …… …… of electrons
An extra shared electron
a shared pair
Hydrogen - covalent bonds
How many extra electrons does H need for a full outer shell? So how many atoms does it bond with?
What does the drawing of the covalent bond look like?
What does the symbol diagram look like?
What does the simple dot and cross diagram look like?
What is the chemical formula for Hydrogen then?
1, 1
The two H atoms in the centre of two circles. The two circles meat like a venn diagram, in between these are a cross and a dot, the atoms’ electrons.
H-H ( - …represents a covalent bond)
H *. H (where *. is a cross above a dot)
H2
Chlorine - covalent bonds
How many extra electrons does Cl need for a full outer shell? So how many atoms does it bond with?
What does the drawing of the covalent bond look like?
What does the symbol diagram look like?
What does the simple dot and cross diagram look like?
What is the chemical formula for Chlorine then?
1, 1
The two Cl atoms in the centre of two circles with dots and crosses all the way round. The two circles meat like a Venn diagram, in between these are a cross and a dot, the atoms’ electrons.
Cl - Cl
Cl *. Cl with the other six dots/crosses around the outside
Cl2
Methane - covalent bonds
How many extra electrons does carbon need for a full outer shell? So how many does must it bond with?
What does the drawing of the covalent bond look like?
What does the symbol diagram look like?
What does the simple dot and cross diagram look like?
What is the chemical formula for methane then?
4, 4
A big circle in the middle, with C inside that, with four crosses around the edge, evenly spaced. Next to each cross is a dot belonging to a hydrogen ring overlapping the carbon ring, like Venn diagrams.
C in the middle with four lines coming out like a cross with Hs on the ends
C with a dot and cross at the top bottom left and right, with an H after each pair of shapes.
CH4
Hydrogen Chloride - covalent bonds
How many extra electrons does Chlorine need for a full outer shell? So how many atoms does it bond with?
What does the drawing of the covalent bond look like?
What does the symbol diagram look like?
What does the simple dot and cross diagram look like?
What is the chemical formula for Hydrogen Chloride?
1, 1
The chlorine atom with a full outer shell but one. One dot is in the Venn gap from a hydrogen atom on its side.
H-Cl
H *. Cl ( with the other three pairs of crosses around it, top bottom and right)
HCl
Ammonia - covalent bonds
How many extra electrons does nitrogen need for a full outer shell? So how many atoms does it bond with?
What does the drawing of the covalent bond look like?
What does the symbol diagram look like?
What does the simple dot and cross diagram look like?
What is the chemical formula for ammonia?
3, 3
N in the middle with one complete pair of crosses at the bottom. On the other three sides the crosses are paired with dots from three H atoms.
H
H- N - H (where the is a line between the top H and the N)
N with one side of two crosses. On the other three sides are one cross and one dot. Hs sit outside the dot and crosses pairs
NH3
Water - covalent bonds
How many extra electrons does oxygen need for a full outer shell? So how many atoms does it bond with?
What does the drawing of the covalent bond look like?
What does the symbol diagram look like?
What does the simple dot and cross diagram look like?
What is the chemical formula for water?
2, 2
O in the middle with two complete pairs of crosses. There are two pairs of dot and cross, the dots belonging to the joint H atoms.
H-O-H
O with two complete pairs of XX, on the other two sides dot X with an H outside of it.
H2O
Oxygen - covalent bonds
How many extra electrons does oxygen need for a full outer shell? So how many atoms does it bond with?
What does the drawing of the covalent bond look like?
What does the symbol diagram look like?
What is the chemical formula for oxygen?
2, 1
Two O atoms next to each other with two sets of XX or . . then in the Venn gap there are . . and XX next to each other, they are sharing 4 between them.
O=O because there are two covalent bonds
O2
What can substances with covalent bonds form?
Simple molecules
The atoms form …. …… covalent bonds to form small …. of several …..
very strong
molecules
atoms
In contrast to a covalent bond how strong are the forces of attraction between molecules made of covalently bonded atoms?
Very weak
What is the result of weak intermolecular forces?
Low melting and boiling points because the molecules can be easily parted.
The stronger covalent bonds between the individual atoms don’t get touched.
What state are most molecular substances in?
Gas or liquid, the can be solid
What do most molecular substances not do?
Conduct electricity as there are no ions so there’s no electrical charge
So simple molecular substances had very weak ….. forces, but very strong ….. forces
inter-molecular
intra-molecular
What are macromolecules?
Giant covalent structures similar to ionic lattices but with no charge
How are the atoms in a macromolecule bonded?
What does this mean for their melting and boiling points?
What don’t they do still (except for graphite) ?
Strongly by covalent bonds
They are very high
Conduct electricity
What are the main examples for macromolecules?
Diamond and graphite, made from carbon atoms
and silicon dioxide (silica)
Diamond - each atom forms how many covalent bonds?
In what kind of structure?
This structure makes diamond the what? So it’s used for..
It’s also ….
A molecular diagram of diamond would look like…
4
Rigid
Hardest natural substance, it’s used for drill tips
Pretty and sparkly
A pyramidal structure with every atom branching off further….
Graphite - each carbon atom only forms how many covalent bonds?
What does this mean? So graphite is … and …. .
How is graphite used as a pencil?
3
This creates layers that are free to slide over each other
Soft and slippery
The layers rub off onto paper due to the weak intermolecular forces between the layers
Graphite is the only ……. that is a good ….. of heat and …….
Each carbon has one… These are what … the heat and ….
non-metal, conductor, electricity
Delocalised electron. Conduct electricity
What does a diagram of graphite look like?
Hexagonal shaped molecule sheets on top of each other with gaps in between the layers with dots joining them, the weak intermoleclar forces.
What is sand made of?
Each grain of sand is one…..
Silicon dioxide (silica) giant structure of oxygen and silicon.
What is so important/different about metallic bonds?
They bond and leave delocalised electrons on the outer shell of every metal atom in the structure, giving metals their properties.
What can electrons in a metal structure do?
So they are good at ….
Move freely through the whole structure
…conducting heat and electricity
How do the electrons effect a metal’s structure? (2)
They hold the atoms together in a regular structure as there is strong electrostatic attraction between the positive metal ions and the electrons.
They also allow the layers of atoms to slide over each other so metals can be bent or shaped.
Alloys are ……… than pure metals
harder
Pure metals often aren’t….
So ………………….. are mixed together to create an …. with the ……
right for the job
two or more metals …. alloy….. properties they want.
How are alloys harder than normal metals?
Different elements have different sized atoms so when two are mixed together, the new atoms will distort the layers making it more difficult for them to slide over each other.
What are the four types of structure?
Giant ionic
Simple molecular
Giant covalent
Giant metallic
