Bonding Flashcards
Define ionic bonding
Ionic bonding involves electrostatic attraction between oppositely charged ions in a lattice
Formula of these ions
Sulfate
Hydroxide
Nitrate
Carbonate
Ammonium
Phosphate
Sulfate - SO4 2-
Hydroxide OH-
Nitrate NO3 -
Carbonate CO3 2-
Ammonium NH4 +
Phosphate PO4 3-
atoms are neutral because …..
number of protons in nucleus = number of electrons
why do many atoms react
Many atoms react in order to achieve the electron configuration of a noble gas
e.g. Sodium can achieve the same electron configuration as neon by losing 1 electron
Chlorine can achieve the same electron configuration as the noble gas argon by gaining 1 electron
Describe what happens in ionic bonding
Example . NaCl
metal reacts with non-metal
In ionic bonding, the electrons are transferred from the metal to the non-metal
In NaCl, the electron in the outer shell of the sodium atom is transferred to the outer shell of the chlorine atom
Because sodium atom has lost an electron, now forms the sodium ion - with charge of 1+
Chlorine atom gained electron - forms ion 1-
both ions have same electron configuration as noble gases
What do the square brackets show in dot and cross diagrams of ionic compounds
The square brackets tell us that the charge is spread over the whole ion
How are ions attracted
These positive and negative charged ions are now attracted to each other by electrostatic forces of attraction
dot cross diagram of magnesium oxide
https://cdn.savemyexams.com/cdn-cgi/image/w=1920,f=auto,width=629,height=446/uploads/2019/12/Magnesium-Oxide-dot-cross-diagram.png
Describe how ionic compounds form a giant ionic lattice
when we react sodium with chlorine, we form a huge number of ions
These ions arrange themselves into a giant ionic lattice
Every ion in the lattice is attracted to every other oppositely charged ion. These are called electrostatic forces of attraction
structure:
Ionic compounds are held together by strong electrostatic forces of attraction between oppositely charged ions. These forces act in all directions in the lattice and this is called IONIC BONDING
Use the idea of the giant ionic lattice to explain the properties of ionic compounds
describe and explain properties of ionic compounds
Very high melting and boiling points
Soluble in polar solvents such as water
Do not conduct electricity when they are solid
cONDUCT ELECTRICITY WHEN MELTED OR DISSOLVED IN WATER
Very high melting and boiling points
Explain this property of ionic compounds
A lot of energy is required to overcome the strong electrostatic forces of attraction BETWEEN THE POSITIVELY AND NEGATIVELY CHARGED IONS. This can only be achieved at high temperatures
Sodium chloride has a melting point of 801 degrees celcius
Magnesium oxide has a melting point of 2852
Explain why
Mg ion has a charge of 2+
O2- ion has a charge of 2-
This means that these ions experience very strong electrostatic forces of attraction
These take a very large amount of energy to overcome
Soluble in polar solvents such as water
Explain this property of ionic compounds
When we dissolve an ionic compound in water, which is a polar molecule, water molecules surround the ions.
This can overcome the electrostatic attraction between the ions and because of this, many ionic compounds can dissolve in polar solvents
If charges on ions increase, what does this mean in terms of solubility
If the charges on the ions increase e.g. in MgO, the solubility often decreases
In this case the water molecules cannot overcome the electrostatic forces of attraction
Do not conduct electricity when they are solids
explain this property of ionic compounds
Ionic compounds do not conduct electricity as solids
This is because the ions are locked in place by the electrostatic forces of attraction
Because the ions cannot move from place to place, they cannot carry a charge
This is because, the ions are fixed in position in a giant lattice. They vibrate but cannot move around and carry a charge
explain why ionic compounds can conduct electricity as liquid or molten
Ionic compounds can conduct electricity when they are melted or dissolved in water.
This is because the ions are free to move and can carry a charge.
Ionic compounds can conduct electricity when molten.
This is because the high temperature provides enough energy to overcome the many strong electrostatic forces between the oppositely charged ions. Ions are free to move around within the molten compound and can carry a charge
Ionic compounds can conduct electricity when dissolved in water.
This is because the water molecules separate the ions from the lattice. The ions are free to move around within the solution and can carry a charge.
Describe what happens if we melt or dissolve an ionic solid in water
Explain why this happens
If we melt an ionic solid or dissolve it in water then it can conduct electricity
This is because in these cases, the ions are now free to move
What do many covalent bonds contain
Multiple bonds contain multiple pairs of electrons
covalent bonding is between
covalent bonding is between two non-metals
Explain what happens when two hydrogen atoms react
Both have one electron in the one S orbital of their outer shell
When the two hydrogen atoms react, their 1s orbitals overlap
And the electrons are now shared between the two atoms (**FULL OUTER SHELL)
This shared pair of electrons forms the covalent bond
single covalent bond is formed
Formed molecule H2
The pair of electrons is attracted to the two nuclei of the atoms forming the bond - called covalent bond
Both atoms now have two electrons in their outer shell - giving them the same electron configuration as the noble gas helium
Why are covalent bonds strong
The pair of electrons is attracted to the two nuclei of the atoms forming the bond - called covalent bond
stick diagram for H2
What does the stick represent
H - H
line represents a shared pair of electrons - a covalent bond
Explain why for F2. H2 and HF
only one covalent bond is formed
Each atom originally required one more electron to achieve the same electron configuration as the nearest noble gas in the periodic table
Not all follow the rule
Having /does not achieve the same electron configuration as the nearest noble gas in the periodic table
E.g. draw BF3
Trigonal planar
the boron atom only has 6 electrons in outer shell
Draw PCL3
has 5 e- in outer shell
only needs 3e- more to achieve outer shell
therefore by forming three covalent bonds, phosphorus will have eight electrons in the outer shell giving it the same electron configuration as the noble gas argon
in this molecule, the phosphorus atom has used three of its outer electrons to form covalent bonds
but that means that phosphorus has a pair of electron in its outer shell which are not used to form a covalent bond - called a lone pair of electrons
What are a lone pair of electrons
A pair of electrons in a non-metals outer shell which are not used to form a covalent bond
Rule breaker:
dRAW PCL5
draw SF6
Has 10 e- in outer shell - PCL5
Has 12 e- in outer shell - SF6 - TO DO THIS SULFUR USES ITS 3D SUB SHELL
Phosphorus is in period 3#
Means phosphorus atoms have the 3D subshell
Because of this, phosphorus atoms can use all five of their outer electrons to form covalent bonds, meaning that the phosphorus atom ends up with ten electrons in its outer shell
Using the d subshell in this way is called expansion of the octet
This cannot take place with elements in periods 1 or 2 as these elements do not have a d sub shell
What is a daive covalent bond (co-ordinate bond)
A co-ordinate (dative covalent) bond contains a shared
pair of electrons with both electrons supplied by one
atom. (in the bond)
EXPLAIN HOW NH4 Is formed from ammonia and H + ion
In ammonia, the nitrogen atom has formed three covalent bonds to hydrogen atoms
This means that the nitrogen atom also has a lone pair of electrons
This means that the nitrogen atom can use its lone pair of electrons to form a covalent bond
E.g. reaction with the H+ ion
Hydrogen ion has no electrons, so it cannot contribute any electrons to a covalent bond
So in this case, the nitrogen atom uses its lone pair of electrons to form a covalent bond to the hydrogen ion
forming ammonium ion NH4 +
When an atom uses a lone pair of electrons to form a covalent bond - called dative bond
Draw displayed formula of ammonia ion
https://s3.eu-west-2.amazonaws.com/elements.cognitoedu.org/36dd8d7e-e6da-4e44-b249-d2f6c2c74b69/ammonium-ion-formation-diagram.png
arrow heaad points away from the element which is providing the lone pair
Rules about dative bonds
For a dative bond to form, the acceptor atom must be electron deficient (there are available orbitals for the electron to occupy)
Dative covalent bond is exactly the same as a normal covalent bond
All of the bonds in the ammonium ion are the same length
All of the bonds have the same average bond enthalpy (tells us strength of bond)
dative bond in nh4+ ion has same bond strength as other bonds
Define metallic bonding
Metallic bonding is the electrostatic attraction between delocalised
electrons and positive ions arranged in a lattice
attraction between lattice of mg 2+ ions and delocalised electrons
describe the structure of a metal
In a metal, the positive metal ions are closely packed together with the negative delocalised electrons and are arranged in regular layers.
Explain why the particles that make up a metal are described as positively charged ions
The particles that make up a metal are described as positively charged ions . This is because, the metal atoms lose their outer shell electrons into a ‘sea’ of (delocalised) electrons,
Therefore, there are more protons (+) than electrons (-)in each metal atom,
more protons (+) than electrons (−), causing the metal ions to become positive.
Define electrostatic attraction
The electrostatic attraction is the attraction between opposite charges
why are metals ductile
have layers of ions
which can slide over each other
explain why Ca has stronger melting point than Sr
Ca has higher mp than Sr because its delocalised electrons are closer to positive ions
Has stronger attraction between + ions and delocalised electrons (stronger metallic bonding)
simple molecular substances
have small molecules with a fixed number of atoms
atoms are covalently bonded to each other
non-polar substances are soluble in/dissolve very well in
non-polar solvents
when substances disolves the solvent molecules form van der waals forces to iodine molecules
