Chemistry - Atomic Structure (C2) Flashcards
Revision on Atomic structure and the C2 Structure
Define Atom
The smallest part of an element that can still be recognised as that element
Define Element
A substance made up of only one atom
Define Molecule
A substance made of two or more different atoms chemically bonded together (can be atoms of the same type)
Define Mixture
A substance made of more than one thing not chemically bonded together
State the three subatomic particles
Protons, Neutrons, Electrons
State the relative charges of the subatomic particles
Protons +1, Neutrons 0, Electrons -1
State the masses of the subatomic particles
Protons 1, Neutrons 1, Electrons 0
How are the subatomic particles arranged in an atom?
Protons and Neutrons in the nucleus and electrons orbiting the outer shells.
What is the plum pudding model?
A ball of positive charge with negative electrons studded into it
What did Rutherford’s alpha scattering experiment prove?
Atoms have a small dense nucleus with a positive charge
How did Bohr adapt the model of the atom?
He said electrons orbit the nucleus at specific distances
What is the atomic number of an atom?
The number of protons in an atom
What is the mass number of an atom?
The number of protons + the number of neutrons in an atom
How do you calculate the number of neutrons in an atom?
Mass number - atomic number
How are the electrons arranged in atoms?
Orbiting the nucleus in shells
How many electrons can go in the first shell?
2
How many electrons can go in the other shells?
8
How were elements arranged in the early attempts of the periodic table?
By atomic weight
How are elements in the periodic table arranged?
By atomic number
How are elements in the periodic table arranged?
By atomic number
What are groups in the periodic table?
The columns, numbered 1, 2, 3, 4, 5, 6, 7, 0/8
What do you know about elements in the same group?
They have similar properties (reactions) as they have the same number of electrons in the outer shell
What can the group tell you about the electrons in an atom?
How many electrons in the outer shell. E.g. carbon is in group 4 so has 4 electrons in the outer shell
What are periods in the periodic table?
The rows in the periodic table
What can the period tell you about the electrons in an atom?
How many shells an atom has. E.g. carbon is in the second period so has two shells
Why did Mendeleev swap the order of some elements?
So they were in the same group as elements they had similar chemical properties with
Why did Mendeleev leave gaps in his periodic table?
For elements that had not been discovered yet
What is an ion?
A charged particle
An atom which has lost or gained an electron
How many electrons does calcium have?
20 (same as atomic number!)
How many electrons does silicon have?
14 (same as atomic number!)
How are the electrons in sulphur arranged?
2.8.6 (18 electrons total)
How are the electrons in magnesium arranged?
2.8.2 (12 electrons total)
How many electrons are in the outer shell of boron?
3 (it is in group 3!)
How many electrons are in the outer shell of phosphorous?
5 (it is in group 5!)
How many electrons are in the outer shell of sodium?
1 (it is in group 1!)
An element has three shells and three electrons in the outer shell. What element is it?
Aluminium (group 3, period 3
How many electrons are in the outer shell of Gallium?
3 (it is in group 3!)
How can solids be separated from liquids?
Filtration
What is crystallisation?
When a solution is heated until crystals start to form then left to cool until all the water evaporates
What does distillation do?
Separates mixture of liquids with different boiling points
What decides what element an atom is?
The number of protons. E.g. carbon always has 6 protons
Why do atoms have no charge?
They have the same number of protons and electrons
What is the approximate radius of an atoms
0.1nm (1x10-10m)
How big is the radius of the nucleus compared to that of the atom?
1/10000 the size (so 1x10-14m)
What is an isotope?
An atom with the same number of protons but a different number of neutrons.
How do you calculate the relative atomic mass of an isotope?
Multiply the isotope mass by the abundance for each isotope, add them together and divide the answer by 100
What type of ions do metals form?
Positive ions as they lose electrons to get a full outer shell - Cations
What type of ions do non-metals form?
Negative ions as they gain electrons to get a full outer shell - Anions
In terms of electrons, what do group 1 (the alkali metals) elements have in common?
1 electron in the outer shell
What do atoms become ions?
To get a noble gas formation as these are very stable
full outer shell
Describe ionic boning
When a metal losses electron(s) to become a positive cation and a non-metal gains these electron(s) to become a negative anion
The anion and cation have strong electrostatic forces of attraction and form an ionic bond
What does a dot and cross diagram show?
How ionic and covalent bonds are formed
See Figure 10
What structures do ionic bonds form?
Giant Ionic Lattice
Describe Giant Ionic Lattices
Regular lattice
Alternating positive and negative ions
(See Figure 11)
What force are Giant Ionic Lattices held together by?
Strong electrostatic forces of attraction between oppositely charged particles
Describe some of the properties of ionic compounds
High melting and boiling point
Conduct electricity as liquids or if dissolved in water but not as solids
Why do ionic compounds have high melting/ boiling points?
Many strong ionic bonds between ions
A lot of energy is required to break these bonds
Why do ionic bonds conduct electricity as liquids or if dissolved in water but not as solids?
In solids the ions are trapped in the regular lattice and thus can not carry charge
In liquids the ions are free to move and can thus carry charge
When dissolved in water the ions separate and are free to move and can thus conduct electricity
Describe covalent bonding
When non-metals bond by sharing electrons
How do covalent bonds work?
The electrons in the outer shell are attracted to the nuclei of both atoms and thus hold them together through electrostatic force of attraction
How strong are covalent bonds?
Very strong
What causes some elements to be diatomic?
They covalently bond to each other to become stable
What are the three models for simple molecular covalent bonds?
Dot and cross
Displayed formula
3D model
(See Figure 12)
What type of substances do covalent bonds form?
Simple molecular or giant covalent structures
How strong are the intermolecular forces attraction in simple molecular covalent bonds?
Very weak
Why are the melting/ boiling points of simple molecular covalent bonds so low?
Despite strong covalent bonds, intermolecular forces of attraction in covalent molecules are very weak and not much energy is needed to separate them
Describe the conductivity of simple molecular compounds
None, they are not charged
Describe a polymer
Chain of repeating monomers
Describe the bonding in polymers
Covalent
How do we draw polymers?
We draw a single repeating unit
See Figure 13
What are macromolecules?
Giant Covalent Structures
Describe properties of macromolecules
High melting and boiling point
Do not generally conduct electricity
- (graphite in an exception)
What 3 Macromolecules do I need to know?
Diamond
Graphite
Silicon Dioxide
What is the boiling point of diamond and why?
Non-existent due to the strong covalent bonds in every direction
(Not possible to create on Earth)
Describe how hard diamond is and why
Diamond is extremely hard due to the strong covalent bonds in every direction
Describe the structure of diamond
Rigid
Forms all 4 potential bonds
(See Figure 14)
Describe the structure of Graphite
Hexagonal layers
Weak intermolecular forces
One free electron per atom
(See Figure 14)
Describe the structure of Silicon Dioxide
One silicon atom for every two oxygen
Very strong covalent bonds
(See Figure 14)
What three Allotropes of Carbon do I need to know?
Diamond
Graphite (graphene)
Fullerenes
What is an allotrope of Carbon?
Different structural forms of carbon in the same state
Describe the conductivity of diamond
None, it forms all four potential bonds and thus does not have any free electrons
Why is graphite soft and slippery?
There are no covalent bonds between layers, only weak intermolecular forces which can be easily broken
Describe the conductivity of graphite
It is conductive of both heat and electricity as it only forms 3/4 potential bonds and thus has a delocalised electron which can carry charge
Describe Graphene
A single layer of graphite
How thick is graphene?
1 atom
Why is graphene used in tents rackets or bows?
It is very light and strong
How many atom molecules are in Buckminsterfullerene?
60 (C60)
Describe Fullerenes
Molecules of carbon shaped as either closed tubes or hollow balls
(See Figure 15)
What are fullerenes used for?
They can trap other molecules so are used to deliver drugs
Have large surface area so can be used as industrial catalysts
Also make good lubricants
What kind of structures do metals form
Giant metallic structures
Describe metallic bonding
The metals loose an electron to form positive cations and the delocalised electrons form a sea around the cations
(See Figure 16)
Why are most metals solid at room temperature?
Electrostatic forces of attraction between ions and delocalised electrons are strong and thus a lot of energy is needed to break this
Why are metals good conductors?
They have delocalised electrons which can carry charge and energy
Why are metals malleable?
All of the ions are the same size and thus can roll over each other easily
What are alloys?
A compound of different metals
Why are alloys harder than pure metals?
The atoms are not all the same size and thus do not slide over each other
What are the three states of matter?
Solid
Liquid
Gas
Describe the structure of a solid
Strong forces of attraction between particles Regular lattice arrangement Particles in a fixed position Fixed shape and volume Particles vibrate (See Figure 17)
Describe the structure of a liquid
Weak forces of attraction between particles Constantly moving in random motion Take the shape of their container Free to move around each other Constant volume (See Figure 17)
Describe the structure of a gas
Very weak forces of attraction between particles Take the shape of their container No definite shape or volume Travel in straight lines Rarely touch (See Figure 17)
What happens when a solid is heated?
Melting
As the particles gain energy the vibrate more
Eventually the bonds between particles weaken and they become a liquid
(See Figure 17)
What happens when a liquid is heated?
Evaporation
The particles gain energy and move around each other faster
Eventually the bonds between particles weaken and they become a gas
(See Figure 17)
What happens when a gas is heated?
The particles gain energy and expand
This increases the pressure
(See Figure 17)
What happens when a solid is cooled?
The particles loose energy and stop vibrating as much
What happens when a liquid is cooled?
Freezing
The particles loose energy and stop moving as much
Eventually bonds form and it becomes a solid
(See Figure 17)
What happens when a gas is cooled?
Condensing
The particles loose energy and stop moving as much
Eventually bonds form and it becomes a liquid
(See Figure 17)
What is sublimation?
When an element goes straight from solid to gas
See Figure 17
What is another name for coarse particles?
Dust
What is the diameter of a coarse particle?
Between 2.5X10^-6m and 1X10^-5m
Between 2, 500nm and 10, 000nm
What is the diameter of a fine particle?
Between 1X10^-7m and 2.5X10^-6m
Between 100nm and 2, 500nm
What is the diameter of a nanoparticle?
Between 1X10^-9 and 1X10^-7
Between 1nm and 100nm
What is the equation for surface are to volume ratio?
Surface area to volume ratio = surface area / volume
Why are nanoparticles useful?
They have large volume to surface area ratios
Why does having a large surface area to volume ratio make for good catalysts?
Reactions happen on the outside of particles, therefore if more of the particle is the surface, more reactions can occur
What could nanoparticles be used for in medicine?
Delivering drugs right into cells when necessary
Why are silver nanoparticles useful?
They have antibacterial properties
What can silver nanoparticles be used for?
They can be put into
- surgical masks
- wound dressings
- deodorant
What are advantages of using nanoparticles in suncream?
Better skin coverage
Protects from harmful UV rays
What are disadvantages of using nanoparticles in suncream?
We do not know if they could harm your body cells
We do not know if once washed away, they may damage the environment
Why should products with nanoparticles be clearly labelled?
We still do not know their long-term effects
