P1 - Atomic Structure and the Periodic Table Flashcards
What is an element?
A substance containing only one type of atom
What is a compound?
A substance containing 2 or more different types of atoms chemically bonded
What is a mixture?
A substance containing 2 or more different types of atoms not chemically bonded
Does filtration separate an insoluble or soluble solid from a liquid?
Insoluble
What equipment do we use for filtration?
- Filter funnel
- Filter paper
- Conical flask
Does crystallisation separate an insoluble or soluble solid from a liquid?
Soluble
When sodium chloride is dissolved in water, what is the solute and the solvent?
The solute is the dissolved sodium chloride
The solvent is the water
What equipment do we use for evaporation?
- Evaporating dish (crucible)
- Tripod
- Bunsen burner
What are the 2 benefits of the separating method ‘evaporation’?
- Quick
- Easy
What is 1 issue of the separating method ‘evaporation’?
Some solids will decompose from the heat (thermal decomposition)
TRUE OR FALSE: We use crystallisation for solids that are susceptible to thermal decomposition
True
Is the separating technique ‘evaporation’ quicker or slower than ‘crystallisation’?
Quicker
How can we heat our solution more gently in crystallisation?
With a water bath
(instead of a bunsen burner like in evaporation)
Do we continue heating the solution when we see start to see crystals forming once some solvent has evaporated in crystallisation?
No
In crystallisation, after heating the solution we leave it to cool and see more crystals. Why is this?
As the solution cools, more crystals will start to form because solids are less soluble at colder temperatures.
How do we dry crystals in crystallisation?
Warming them in an oven.
What’s an aqueous solution?
A solution in water
When do we use simple distillation?
When we want to separate a dissolved solid from a liquid but want to keep the liquid
In short, how do we carry out simple distillation?
- Evaporate the liquid by heating which turns it into vapour
- We condense the vapour back to a liquid by cooling
How do we carry out simple distillation? Full answer
Hints:
1- Vapour
2- Glass tube, thermometer
3- Boiling, vapour, condenser
4- Condenser, condense
5- Beaker, flask
The heated solution turns into vapour.
As it rises up the glass tube the thermometer reading increases.
We continue heating until the solution is boiling and then the vapour is in the condenser.
The condenser contains circulating cold tap water which causes the vapour to condense into a liquid.
We collect the liquid in a beaker and we’re left with crystals of the solid in the flask
In simple distillation, does the condenser heat or cool the vapour?
Cools
TRUE OR FALSE: We can use simple distillation to produce drinking water
TRUE: However it’s not recommended since lots of energy is used up
Extra: We have other, more efficient techniques for this
When do we use fractional distillation?
When we want to separate several liquids with different boiling points
What are the hundreds of glass beads in fractional distillation called?
Fractionating column
How do we carry out fractional distillation?
Hints:
1- Heat, evaporate
2- Condense, fractionating column, flask
3- Lower boiling point chemical, fractionating column
4- Thermometer, mixture, lower boiling point
5- Condenser, liquid, mixture
6- Thermometer, stops, condensed, fresh beaker
7- Thermometer
8- Thermometer, stops, condensed, fresh beaker
9- Separation
We heat the mixture and both liquids will begin to evaporate.
The 2 vapours condense in the fractionating column and drip back into the flask.
This repeated process increases the amount of the lower boiling point chemical in the factionating column.
The themometer reading rises as the vapours reach it but the mixture contains more of the lower boiling point.
They pass through the condenser and turn into a liquid but are still a mixture
The thermometer reading stops rising and that’s when the lower boiling point chemical gets condensed and drips into a fresh beaker
The reading rises again
The reading stops rising again and the higher boiling point chemical gets condensed and drips into another fresh beaker
Now they’re separated!
During fractional distillation, what are the 2 factors that mean we either can’t separate the liquids or struggle to?
- Similar boiling points: We may need to carry out multiple rounds
- Large volume (e.g. crude oil) : The equipment we use isn’t suitable
What do all separation techniques have in common?
Being a physical process
Extra: This means they don’t involve chemical reactions
No new substances are made
What does paper chromotography allow us to do?
To separate substances based on their different solubilites
How do we carry out the chromotography paper experiment?
Hints:
1- Chromotography paper
2- Pencil
3- 2 colours
4- Paper, solvent
5- Solvent, ink, 2 colours
6- Ink
1- Take chromotography paper
2- Draw a pencil line near the bottom
3- Put a dot of the first colour on the pencil line and next to it, place another dot of a second colour
4- Place the bottom of the paper into a solvent
5- Solvent moves up the paper and dissolves the ink in the 2 coloured dots
6- The ink is carried up
What do we call the paper in paper chromotography?
Stationary phase
Extra: Because it doesn’t move
What do we call the solvent in paper chromotography?
Mobile phase
Extra: Because it moves
How do you know a colour is a pure colour in paper chromotography?
There’s only 1 spot of the single colour
How do you know a colour is a mixture of colours in paper chromotography?
The single colour has separated into more than 1 different spots
TRUE OR FALSE: In paper chromotography, a pure compound will produce 2 spots of a single colour in all solvents
FALSE: A pure compound will produce a single spot in all solvents
In paper chromotography, will the compounds in a mixture separate into different spots depending on the solvent?
Yes
Why does paper chromotography work?
Because different substances have different solubilities
TRUE OR FALSE: In paper chromotography, a more soluble substance is more attracted to the mobile phase (solvent) than a less soluble substance
TRUE
In paper chromotography, does a less soluble substance travel further than a substance which is more soluble?
No
A MORE soluble substance travels further than a LESS soluble substance
Common exam question for paper chromotography:
WHY DO WE DRAW OUR STARTING LINE IN PENCIL?
Because if we drew the line in pen, the pen ink could dissolve in the solvent and move up the paper
What’s a solvent?
A liquid that will dissolve substances
For paper chromotography, how many colours can we use?
Several colours
Extra: As long as there’s enough space
Why was the alpha scattering experiment used?
To find out if the Plum Pudding Model was correct
What happened in the alpha scattering experiment + how was it carried out?
Hints:
1- Gold foil
2- Particles
3- Through
4- Deflected
5- Bounced
- Piece of gold foil because it’s easy to hammer down gold into a few atoms thick
- Tiny alpha particles were fired at the gold foil
- Most alpha particles went straight through
- Some alpha particles were deflected
- Some alpha particles bounced straight back
In the alpha scattering experiment, what did scientists find out because most alpha particles went straight through the gold foil?
That atoms are mainly empty space
Extra: They immediately knew the plum pudding model was wrong
In the alpha scattering experiment, what did scientists find out because some alpha particles were deflected?
The centre of the atom has a positive charge
In the alpha scattering experiment, what did scientists find out because some alpha particles bounced straight back?
The centre of the atom contains lots of mass
What model was the Plum Pudding Model replaced with?
The Nuclear Model
What charge do alpha particles have?
Positive
Why would alpha particles get deflected when going near the positive centre of an atom?
Alpha particles are positive so they would be repelled and change direction
In the nuclear model, how much of the atom is empty space?
In the nuclear model, most of the atom is empty space
What scientist proposed the idea that electrons orbit the nucleus in an atom?
Niels Bohr proposed the idea
What do we call the orbits in an atom?
- Energy levels
OR - Shells
Why does the nucleus have a positive charge?
The nucleus has a positive charge because of protons
What determines the amount of positive charge in the nucleus?
Number of protons determines it
What scientist discovered that the nucleus contains neutrons
James Chadwick discovered it
What’s the radius of an atom?
0.1 nanometres (1x10^-10 m)
What’s the radius of the nucleus?
1x10^-14 m
TRUE OR FALSE: Half of an atom’s mass is found in the nucleus
FALSE: Nearly all of the mass of an atom is found in the nucleus
TRUE OR FALSE: Atoms have no overall charge
TRUE
What’s the relative charge and relative mass of:
Protons, neutrons, electrons
Proton = +1, 1
Neutron = 0, 1
Electron = -1, very small
What are isotopes?
Isotopes are atoms of the same element with different numbers of neutrons
What are ions?
Ions are atoms which have an overall charge
Extra: Because they have lost or gained electrons
What does the number of electrons in the outer energy level tell us?
The group number of that element on the periodic table
What is group 0 on the periodic table called?
Noble gases
Are the metal elements in group 1 highly unreactive or reactive?
Reactive
Are the non-metals in group 7 highly unreactive or reactive?
Reactive
Why do elements in the same group have similar chemical properties?
They have the same number of electrons in their outer energy level
Who called elements that came in threes “triads”?
Johann Dobereiner
What do lithium, sodium and potassium all react rapidly with?
Water
Who ordered the elements in order of increasing atomic weight?
John Newlands
Who created “law of octaves” (every 8th element reacting in a similar way)?
John Newlands
What was a problem with John Newlands’ law of octaves?
Some elements with very different properties were grouped together
Who developed the 1st modern periodic table?
Dmitri Mendeleev
How did Dmitri Mendeleev creat the periodic table?
Firstly, he arranged all elements in increasing atomic weight
However, he would swap specific elements so they fitted other elements in the same group
Secondly, he left space for undiscovered elements
What did Mendeleev predict correctly?
The undiscovered elements for where he left the gaps in the periodic table
What’s 1 difference between Mendeleev’s periodic table and the modern periodic table?
They are now arranged in order of atomic number (number of protons)
Why is ordering elements by atomic weight wrong?
Some will appear in the wrong order due to isotopes
What group on the periodic table was not fully discovered at Mendeleev’s time?
Group 0
Are the noble gases very unreactive or very reactive elements?
Very unreactive
Why are some elements unreactive?
- Full outer energy level
When are atoms stable?
When they have a full outer energy level
Do the noble gases have boiling points of above or below room temperature?
Below
Do the boiling points of the noble gases increase or decrease as the relative atomic mass increases (moving down group 0)
Increase
Where do we find metals on the periodic table?
On the left and the centre
Where do we find non-metals on the periodic table?
On the right side
When metals react, do they lose or gain electrons?
Lose electrons to achieve a full outer energy level
When metals achieve a full outer energy level, what electronic structure does it give them?
The electronic structure of a group 0 noble gas
TRUE OR FALSE: Metals always form negative ions
FALSE: Metals always form positive ions
