3.1.3 Bonding Flashcards
Substance
Made out of one repeating unit
What is a mixture
Made out of different repeating units
What is a compound?
A substance containing atoms of more than one element
What is the electron sea model
Metals are made up of a lattice of cation surrounded by a sea of delocalised electrons.
How do delocalised electrons allow a metal to conduct electricity
They are freely moving throughout the metal and are charged
What is metallic bonding?
The electrostatic attraction between cations and delocalised electrons.
Why are metals malleable and ductile?
The layers of cations can slide over each other without breaking any metallic bonding
Why do metals have high melting and boiling point?
They have strong electrostatic attraction between the cation and delocalised electrons
Why does the melting point of metals increase across a period?
Group 1 metals form + charges
Group 2 metals form 2+ charges
Group 3 metals form 3+ charges
This means that as they go across the melting point increases as they form metallic bonding with more higher charged cations
Down a group, the melting point….
Decreases.
This is because the size of the cations increase which means theres a larger distance between the nucleus and outer electrons so there are weaker attraction
State and explain the general trend in melting point if the period 3 metals.
Across a period the charge of the cation increases, so there is a stronger attraction between the cation and delocalised electrons.
This stronger attraction means the strength of the metallic bonding increases across a period and so therefore the melting point too
What are positively charge ions called?
Cations
What are negatively charged ions called?
Anions
Define ionic bonding.
Electrostatic forces of attraction between oppositely charged ions formed by electrons transfer
What are the simplest ion
a single atom which have either lost/gain electrons so that they’ve got a full outer shell.
What are ionic crystals called?
giant lattice of ions.
Is the melting a point of ionic compounds high or low?
High
Charge of sliver
+
Charge of Zinc
2+
Charge of iron
2+/ 3+
Charge of copper
+\2+
Charge of lead
2+\4+
Sulfate ion and charge
So4(2-)
Nitrate ion and charge
NO3(-)
Manganate ion and charge
MnO4(2-)
Phosphate ion and charge
PO4 (3-)
Hydrogen carbonate ion and charge
HCO3(-)
Hydroxide ion and charge
OH(-)
What state can ionic compounds conduct electricity
Liquid or molten as they are free to move around.
Why do ionic compounds have high melting and boiling points?
There is a strong attraction between the cations and anions
The larger the charge between two charges the ___ the ionic bonding is
Stronger
The ____ the distance between two ions the _____ the ionic bonding
- Larger
- Weaker
Down a group the size of ions…
Increases
When are covalent bonds formed
When atoms share a pair of electrons
Examples of micromolecular structures
- Graphite
- Diamond
what is the structure of graphite?
Carbon is arranged in sheets of flat hexagon. The fourth outer electron of each carbon atom is delocalised.
what property graphite used as dry lubricant and pencils
the weak bonds between the layers in graphite are easily broken, so the sheets can slide over.
explain why graphite is a good electrical conductor.
the delocalised electrons in graphite aren’t attached to any carbon. Therefore, are free to move and can conduct electricity.
Explain why graphite has a very high melting point.
They have strong covalent bonds which need high amounts of energy to overcome.
Explain why graphite is insoluble in any solvent.
The covalent bond s are too strong to break so therefore they aren’t able to dissolve.
Substance made of molecules have
- Low melting and boiling point
- Dont conduct electricity
what is diamond made up of?
it is made up of carbon atoms. Each carbon atom is covalently bonded to four other carbon atoms. They arrange themselves in a tetrahedral shape.
Properties of diamond:
- very high melting point
- good thermal conductor
- can’t dissolve in any solvent.
What is a dative bond
One atom contributes both electrons to the shared pair
To have a dative bond you need..
A dative bond donor- a lone pair of electrons
What is valence bond theory?
It states that if two atoms have orbitals which contain unpaired or single electrons then the orbitals will overlap, forming a covalent bond.
Sigma bonds
Overlap end on
Pi bonds
Overlap side on
What will an oxygen-oxygen double bond form
One pi bond and one sigma bond
What will two nitrogen atoms form when triple bonded?
1 sigma bond and 2 pi bond
What do double bonds consist of?
All double bonds consist of one sigma bond and one pi bond.
What do single bonds consist of
Sigma bonds
What is electronegativity
An atoms’s ability to attract electrons in a covalent bond
What are the two factors that determine the strength of ionic bonding?
1.The charge.
Larger charge=stronger ionic bonding
- Larger ions.
Larger ions = weaker ionic bonding.
What is an isoelectric ion?
Ions with the same number of electrons
How could we determine the size of isoelectric ions?
As they have the same number of electrons, the ions with the higher nuclear changes is the smallest.
Are ionic compounds soluble or insoluble?
Soluble in water
Can ionic compounds conduct electricity?
Yes! When they are molten
What are atoms in molecules held together by?
Covalent bonds
What is a molecule?
An uncharged group of two or more atoms stuck together
What is a covalent bond?
When two atoms share a pair of electrons.
What are the two factors that affect the length of a covalent bond?
- The size of the atoms
Larger atoms form longer bonds - Single,double or triple bond.
Single is the longest and triple is the shortest .
The shorter a bond, the ____ the covalent bond is.
Stronger
What is a dative covalent bond?
When one atom contributes both electrons to the shared pair.
What is a dative bond represented with?
——>
When do dative bonds form?
Generally with species that have a lone pair.
Do covalent bonds have higher or low melting and boiling points?
Low melting and boiling point!
Can covalent compound conduct electricity?
No they can’t
Where does the electron pair typically lie?
Close to the more electronegative atoms
What are the trend in electronegativity across a period?
It increases across a group of
What are the trends in Electronegativity across a period?
Increases across a period.
What are the trends in Electronegativity across a period?
Increases across a period.
What are the trends in Electronegativity down a group?
Decreases down a group
What are intermolecular forces?
Forces between molecules.
What are the three types of intermolecular forces?
Dipole-dipole
Van der waals
Hydrogen bonding
What are dipole dipole forces?
These form between molecules with permanent dipoles/ polar molecules.
What is hydrogen bonding?
When a hydrogen is directly bonded to a N/O/F
What are van der waals forces?
When the movement of of electrons in a molecules create s temporary dipoles
What force do all molecules have?
Wan der waals forces
When melting and boiling a substance what gets weakened?
The intermolecular forces not the bonding eg covalent bonds
Are non polar molecules soluble?
No they aren’t
Only polar are soluble
What are molecular solids?
Solids that are held together by intermolecular forces
Examples of intermolecular solids?
Ice
Iodine
What is a macromolecule?
A massive Covalently bonded molecule which consists of thousands of atoms
When a lattice is made up of macromolecules what do we call it?
Giant covalent lattice
What is diamond?
A macromolecule held together by covalent bonds between carbon atoms
In diamond each carbon atom bonds to how many other carbon atoms?
4 other carbon atoms
In graphite each carbon atom bonds to how many other carbon atoms ?
3 different carbon atoms
What is graphite?
A macromolecule with sheets held by intermolecular forces (vdw).
What are allotropes?
The different structures that can form when atoms of that element bond together.
Eg carbon made diamond and graphite
Why do graphite have delocalised electrons?
In graphite, each carbon uses 3 electrons to make single bonds to other carbon atoms. This leaves one electron in the 2p orbital. These 2p orbitals overlap and have delocalised electrons.- bonding between carbons are strong due to this
Why can graphite conduct electricity but diamond can’t?
Graphite has delocalised electrons which can move freely between each layer and carry a charge. Diamonds outer electrons are in a covalent bond so there are not delocalised electrons to carry a charge.
Why is graphite so soft?
As to separate the layers in graphite you only need to break the weak intermolecular forces between them.
Why is diamond so hard?
You need to break strong C-C bonds
Why do graphite and diamond have high melting points?
as you need to break the string covalent bonds between the carbon atoms
