Bonding Flashcards by A A

Define ionic bonding

Ionic bonding involves electrostatic attraction between oppositely charged ions in a lattice

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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-

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atoms are neutral because …..

number of protons in nucleus = number of electrons

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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

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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

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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

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How are ions attracted

These positive and negative charged ions are now attracted to each other by electrostatic forces of attraction

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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

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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

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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

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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

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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

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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

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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

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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

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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