SC5,SC6 & SC7 Flashcards
What are bonds?
Bonds are forces of attraction that holds atoms together
What happens when bonds form between atoms?
Energy is released from the atoms which makes them more stable (less reactive)
More stable with a full outer shell
How are ions formed?
It’s the transfer of electrons between atoms which form charged particles (ions)
What is ionic bonding?
Metal and non metal
What happens when metals react?
They lose outer shell elections to leave a full electron shell
What happens when non-metals react?
They gain electrons to achieve a full electron shell
What are cations?
When metals lose electrons to form positive ions
What are anions?
When non-metals gain electrons to form negative ions
What are electrostatic forces?
The force of attraction between all positively and negatively charged objects
Hold oppositely charge ions together and form an ionic bond between them
How many electrons are lost or gained in group 1 elements?
What is the charge on the ion?
1 electron is lost
1+
How many electrons are lost or gained in group 2 elements?
What is the charge on the ion?
2 electrons are lost
2+
How many electrons are lost or gained in group 6 elements?
What is the charge on the ion?
2 electrons are gained
2-
How many electrons are lost or gained in group 7 elements?
What is the charge on the ion?
1 electron is gained
1-
What are ionic compounds?
They’re formed by the loss and gain of electrons
Held together by strong electrostatic forces of attraction between oppositely charged ions
What is a lattice structure?
The strong bonds allow ‘billions’ of ions that are packed together in a regular repeating arrangement called a lattice structure
What is the formula of ionic compounds?
Needs to contain the same number of positive charges as negative charges
What are the melting and boiling points like in ionic compounds?
The forces are strong
A lot of energy needed to overcome forces
Need to be heated on high temperatures before they change state
High melting and boiling points
What happens if an ion has more than 1 charge?
They attract other ions more strongly than ions with 1 charge
More energy needed to overcome electrostatic forces of attraction
Melting points = higher
When do ionic compounds conduct electricity?
When they are molten or dissolved in water
Not when they are solid
What are the conditions for a substance to conduct electricity?
Must contain charged particles (carry the current)
Particles must be free to move
Where are the negative ions (anions) attracted to?
They’re attracted to the positive electrode, called the anode
Where are the positive ions (cations) attracted to?
They’re attracted to the negative electrode, called the cathode
Do the ions or electrons move to conduct electricity?
The ions moving enable ionic compounds to conduct electricity
What are molecular substances?
Contain groups of atoms that are held together by strong bonds called covalent bonds
What is a covalent bond?
When are covalent bonds formed?
A covalent bond is a shared pair of electrons
When non-metals react together
Produced by sharing pairs of electrons
What happens when the bond forms?
It makes the atom more stable as they use the shared electrons to complete their outer shell
E.g noble gases
What are the forces of attraction like in the bonded atom?
Strong electrostatic forces between the positive nuclei and negative electrons
Weak forces between molecules (intermolecular forces), doesn’t take much energy to overcome the weak intermolecular forces
What are compounds?
Compounds contain atoms of more than one element, chemically joined together by bonds
What is the conduction of electricity like in molecules?
They can’t conduct electricity as the electrons are free to move as there are strong electrostatic forces that hold the negatively charged electrons and positive nucleus together
What is a polymer?
A polymer is formed when monomers (small,simple molecules) are joined in a chain
What do most polymers contain?
Contain a chain of carbon atoms
What are the features of longer polymers?
More intermolecular forces between them
Have higher melting and boiling points than shorter ones
What are allotropes?
Different forms of the same element
What are fullerenes?
Simple molecules formed by carbon in which each carbon atom is covalently bonded to 3 other carbon atoms
What are the features of fullerenes?
They have weak intermolecular forces between molecules
Low melting point and boiling point
Soft and slippery
Molecules strong due to covalent bonds
What is graphene?
Not a simple molecule
Consists of sheets of carbon atoms with no fixed formula
Light (one atom thick) but covalent bonds make it very strong
Is graphene a good electrical conductor?
Yes it is because it’s electrons are free to move to across the surface
Name to allotropes of carbon that aren’t simple structures?
Diamond and graphite (covalent, giant molecular structures)
What is the melting point in diamond and graphite?
The melting point is high as it has strong covalent bonds that need lots of energy to be broken
How many covalent bonds does graphite have?
3 covalent bonds for each atom
Gives a layered structure so not all electrons are held together in covalent bonds
What are delocalised electrons?
Electrons that are free to move and can carry an electrical current
Graphite is a good conductor (and cheap and not reactive)
Why is graphite soft?
Held together by weak forces of attraction which allow layers to slide past each other
How many covalent bonds does diamond have?
Held together by 4 covalent bonds
What is the structure like in diamond?
Rigid network of carbon atoms in a tetrahedral arrangement, held together by strong covalent bonds
What is diamond useful for?
Tools
Is diamond an electrical insulator?
Yes it is because it has no free charged particles
What happens to the lecterns in the outer shell of metal atoms?
Lost from each atom and become free to move randomly throughout the metal
What happens once the outer electrons are lost from the metal atom?
They form a giant lattice of positive metal ions surrounded by a sea of delocalised electrons
What is metallic bonding?
Electrostatic attraction between the positive ions and the negative delocalised electrons
Attraction is strong so metals have high boiling and melting points
Why are metals malleable?
The layers of ions slide over each other when the metal is hit
Sea of electrons holds ions together so metal changes shape
How do metals conduct electricity?
Delocalised electrons move randomly between positive metals in all directions
When voltage applied, electrons move to positive side so transfers energy and forms an electrical current
Why do some substances conduct electricity better than others?
The electrical conductivity of metals increases as the number of delocalised electrons increases
Which has a higher electrical conductivity: magnesium or sodium?
Magnesium as it has a 2+ charge so contributes 2 electrons to the sea of electrons whereas sodium has a 1+ charge so only contributes 1 electron to the sea of electrons
Magnesium has better electrical conductivity than sodium
What are simple molecules?
Non metal elements and compounds
What are the properties of simple molecules?
Low melting/boiling points
Few soluble in water
Most don’t conduct electricity
What are the bonds like between giant covalent?
Covalent bonds formed when atoms share pairs of electrons
What are the properties of giant covalent structures?
High melting/boiling points
Insoluble in water
Most don’t conduct electricity (carbon as graphite does)
What is the structure of metallics?
Billions of ions held together in a giant lattice structure of positive ions in a sea of negative delocalised electrons
What is the properties of metallics?
High melting/boiling points
Insoluble in water
Conduct electricity when solid or liquid
