AS and Periodic table Flashcards
What is meant by an atom?
An atom is the smallest part of an element that can exist.
What is meant by an element?
A substance that consists of only one type of atom.
What is meant by a compound?
A substance composed of two or more different elements chemically bonded together in fixed proportions.
What is meant by a mixture?
Two or more substances not chemically bonded together.
What is meant by a molecule?
2 or more different or same elements chemically bonded together.
Describe the properties of compounds in comparison to they elements it’s made from?
- Properties of compounds are different to properties of the elements they are made from.
Describe the properties of mixtures in comparison to the elements they are made from.
The properties of a mixture are the same as that of the elements they are made from. The properties are unchanged.
How can compounds be separated?
Through chemical reactions
How can mixtures be separated?
Through physical separation processes
How are compounds formed?
From chemical reactions.
What 2 things do chemical reactions always involve
- The formation of new substances
- A detectable energy change
What is filtration used to separate?
Insoluble solids from liquids.
eg X(s) from Y(l)
Summarise the process of filtration
- Place filter paper in filter funnel
- Put filter paper and funnel in a conical flask
- Pour the mixture into the filter paper
- The filter paper contains pores that allow liquid to pass through
- The insoluble solid will remain in the filter paper as it can’t pass through the pores, this is called the residue.
- The liquid will pass through the filter paper pores into the conical flask, and this is called the filtrate.
Give an example of filtration:
Filtering rock from water
What is crystallisation used to separate?
Soluble solids from liquids.
eg X(aq) from Y(l)
Summarise how crystallisation works:
- Leave solution in apparatus such as beaker for a few days.
- Water(or any liquid) evaporates
- Leaving behind crystals of solid substance that was once dissolved in the liquid.
OR
- Place solution in evaporating dish
- Heat evaporating dish GENTLY on Bunsen burner flame for water/liquid to evaporate
- This leaves behind crystals of the solid substance that was once dissolved in the liquid.
Why do scientists prefer evaporation over a few days rather than with a Bunsen burner during crystallisation?
- Because with a bunsen burner some chemicals break down due to heat (thermal decomposition).
- This effects the properties of the solid crystal produced (they will change).
Give an example of crystallisation:
Sodium chloride,NaCl, from salt water.
(salt from salt water to make salt crystals).
What is simple distillation used for?
To separate a dissolved solid from a liquid while also keeping the liquid.
What 2 main processes does simple distillation include, to obtain the liquid?
- Evaporation of liquid by heating.
- Condensation of liquid by cooling.
Describe the set-up for simple distillation.
- Flask connected to continuous glass tube
- Beaker at the end of continuous glass to collect liquid
- Glass tube is surrounded by a condenser that keeps the internal glass tube cold
- Cold water continuously runs in and out of the condenser
- Thermometer is also part of the apparatus
(Look at image).
Example of what simple distillation can be used for.
Production of drinking water from sea water.
A lot of energy is required from simple distillation so other techniques are used to do this.
Why is simple distillation not commonly used to provide drinking water from sea water?
A lot of energy is required from simple distillation so other techniques are used.
Explain the process of simple distillation.
- Solution is heated in a flask using a Bunsen burner until it boils.
- Liquid evaporates and turns into vapour.
- Vapour rises and as it rises the thermometer reading increases.
- Vapour passes into the continuous internal tube that is surrounded by a condenser.
- The condenser is cold bc tap water is continuously circulating around it.
- This causes the vapour to condense to a liquid
- The liquid is passed into the beaker
- And we are left with solid crystals in the flask and liquid in the beaker.
What is fractional distillation used to separate?
- A mixture of different liquids with different boiling points, from each other.
Example of simple distillation?
Separating seawater from salt to keep salt and sea water.
Example of fractional distillation?
Separating crude oil into diff hydrocarbon chain lengths.
or
Water from vinegar
What does the set up of fractional distillation have that simple distillation doesn’t?
A fractionating column containing glass beads.
Explain the process of fractional distillation.
- Start by gently heating the liquids in the flask using a bunsen burner
- Liquids will begin to evaporate to form a vapour, but the liquid with the lower boiling point evaporates more easily.
- As the mixture of vapours rise, they reach the fractionating column.
- There, the condense and drip back into the flask where they evaporate again.
- The repeated condensation and evaporation increases the amount of the lower BP liquid vapour in the fractionating column.
- So eventually the vapour of the lower BP liquid will travel ahead of that of the higher BP liquid in the fractionating column.
- So the thermometer reading will increase to show a mixture of vapours is passing through.
- Vapours pass into the condenser and condense into the beaker.
- This is still a mixture of liquids but mainly the lower BP liquid.
- This process continues until the temperature on the thermometer reading stops rising and reaches a constant temperature, the vapour sample is relatively pure.
- This shows that only the vapour of the lower BP liquid is passing thru.
- Now we collect this liquid in a fresh beaker.
- After some time the temperature of thermometer reading will begin to rise again until it reaches a constant temperature.
- Bc vapour of higher BP is passing over it.
- This will condense - collect this in another fresh beaker.
^^NOT USEFUL FOR LARGE VOLUME EG CRUDE OIL
If the two liquids in fractional distillation have a VERY similar boiling point, what should we do and why?
- It will be harder to separate these liquids so
- Carry out several rounds of fractional distillation
Chromatography
Look at other flashcards
State 1 way a scientific model could be replaced or changed?
If new experimental evidence is proposed/released.
Explain how the modern nuclear model of the atom came about.
- Ancient greeks believed atoms were tiny spheres that couldn’t be divided.
- Then the electron was discovered leading to the Plum Pudding Model of the atom; atom is a ball of positive charge w negative electrons embedded within it, by JJ Thompson.
- Scientists wanted to see if PPM is true so conducted the Alpha Scattering Experiment
- They fired tiny alpha particles at gold foil from an alpha particle source.
- Alpha particles have a positive charge, and gold foil was used bc it can be hammered to a few cm thick.
OBSERVATIONS + CONCLUSIONS - Most alpha particles passed straight thru gold foil w no change in direction; atoms are mainly empty space (PPM = wrong)
- some alpha particles deflected; centre of atom/nucleus = positive charge bc + alpha particles were repelled (PPM = wrong)
- sometimes alpha particles bounced straight back; mass of atom concentrated in the centre of it/nucleus. (PPM = wrong)
- Then, after carrying out calculations which experimental data supported, Bohr discovered that electrons orbit the nucleus at specific distances called energy levels, this meant the alpha scattering = wrong bc suggested they were all at one level.
- Later experiments showed that the positive charge of the nucleus could be divided into a WHOLE number of smaller particles which each have the same amount of positive charge, these are called protons.
- Then Chadwick provided evidence for the existence of neutrons (this idea was alr accepted for abt 20 yrs)
Why did the new evidence from the scattering experiment lead to a change in the atomic model
- Alpha particles have a positive charge, and gold foil was used bc it can be hammered to a few cm thick.
OBSERVATIONS + CONCLUSIONS - Most alpha particles passed straight thru gold foil w no change in direction; atoms are mainly empty space (PPM = wrong, bc it said that ball of positive charge with negative electrons embedded within it)
- some alpha particles deflected; centre of atom/nucleus = positive charge bc + alpha particles were repelled (PPM = wrong bc it said atom was ball of + charge, this says + charge is ONLY in centre)
- sometimes alpha particles bounced straight back; mass of atom concentrated in the centre of it/nucleus. (PPM = wrong, bc PPM suggest mass is everywhere, and that mass isn’t concentrated in nucleus, it doesn’t acknowledge one)
Describe the differences between the plum pudding model of the atom and the nuclear model of the atom (4 marks)
- PPM atom mass spread evenly throughout NM mass is concentrated in the centre.
- PPM negative electrons are embedded within atom uniformly, NM negative electrons are found at the edge of the atom.
- NM, atom is mainly empty space, PPM - negatively charged electrons embedded throughout so not empty space.
- PPM electrons and protons are distributed uniformly
NM electrons on edge and protons in middle.
What is the radius of the atom?
0.1nm or 1 x 10^-10m
What is the radius of the nucleus?
1 x 10^-14m (less than 1/10 000 of that of an atom)
Where is the mass of an atom concentrated?
In its nucleus.
What is meant by the relative mass of a particle?
The mass of one particle compared to another particle.
What is meant by the relative charge of a particle?
The charge of one particle compared to another particle.
Relative masses of protons neutrons and electrons:
P = 1
N = 1
E = very small
Relative charges of protons neutrons and electrons
P = +1
N = 0 (don’t have charge)
E = -1
Explain why atoms have no overall charge (2 marks)
- They have the same number of protons which are positive as electrons which are negative.
- So their charges cancel out
What is the bottom number on an atom?
The atomic number (represents the number of protons in an atom /and electrons of not an ion)
What is the top number?
The Relative atomic mass number (represents the sum of the protons and neutrons in an atom), Ar.
What does the mass number represent?
The sum of the protons and neutrons in an atom.
How to work out no. of neutrons?
Mass no. - Atomic no.
(top - bottom)
What is meant by an isotope?
Atoms of the same element with a different number of neutrons but the same number of protons.
What is meant by an ion? (2 marks)
An atom that has an overall charge (1) due to the loss or gain of electrons (1).
Have positive ions lost or gained electrons?
Lost. (to become more positive)
Have negative ions lost or gained electrons?
Gained. (to become more negative)
Can you do this?
Students should be able to calculate the numbers of protons, neutrons and electrons in an atom or ion, given its atomic number and mass number.
Yes = good
No = practice
What do electrons orbit on in atoms?
Energy levels/shells
Each energy level can hold how many electrons (up to fourth)
1st shell = 2 electrons
2nd shell = 8 electrons
3rd shell = 8 electrons
4th shell = 18 electrons
How do we write to display the number of electrons in each shell of an atom?
[x,y,z]
where x y and x represent a new shell.
How can we work out which group each atom is from?
From the number of electrons in their outermost energy level.
Eg Lithium, Li has 1 electron in its outermost energy level, this means its in group 1 of the Periodic table.
elements with a full outermost shell are found in which group?
Group 0, noble gases
How are elements in the periodic table arranged and why? 2 marks
- In order of atomic (proton) number
- So that elements with similar properties are in columns, known as groups.
Why is the periodic table called the periodic table?
because similar properties within elements occur at regular intervals.
Explain how the position of an element in the periodic table is related to the arrangement of electrons in its atoms and hence to its atomic number.
Elements positioned in the same group in the periodic table have the same number of electrons in their outer shell.
So they have similar chemical properties and react in a similar ways.
Describe the steps in how the periodic table was developed by Mendeleev.
- He arranged atoms in order of atomic weight, but not strictly.
- He switched the order of specific elements so they fitted the pattern of their groups, when necessary.
- He left gaps in the PT for elements that hadn’t been discovered and predicted their properties based on the other elements in the same group.
^^when the elements were discovered, they matched the predictions which led to scientists taking him seriously.
Elements with similar properties in the periodic table are found in what?
Groups.
Explain why elements in the same group have similar chemical properties/react in a similar way.
they hv the same number of electrons on their outermost shell.
Summarise the changes to the periodic table that led to the modern periodic table.
1 - Dobereiner’s Triads
- noticed that elements w similar chemical properties often occurred in threes called triads.
- this led scientists to wonder if elements could be arranged in a logical order
2 - Newlands’ Law of Octaves
- Arranged elements in order of increasing atomic weight and saw that every 8th element reacted in a similar way.
- However the law of Octaves wasn’t taken seriously by scientists because it broke down after calcium and it meant that elements were grouped tg even if they had v diff chemical properties.
3 - Mendeleev and the 1st modern PT
- He arranged atoms in order of atomic weight
- He switched the order of specific elements so they fitted the pattern of their groups, when necessary.
- He left gaps in the PT for elements that hadn’t been discovered and predicted their properties based on the other elements in the same group.
^^when the elements were discovered, they matched the predictions which led to scientists taking him seriously.
Issues w Newlands’ law of Octaves
- Placed elements STRICTLY in order of atomic weight
- This meant some elements were placed in inappropriate groups ie completely diff properties.
What was wrong w Mendeleev’s Periodic table?
He arranged some elements in order of atomic weight, instead of proton number, this is because protons hadn’t been discovered yet.
However knowledge of isotopes made it possible to explain why the order based on atomic weights was not always correct.
How did knowledge of isotopes allow scientists to know that ordering the PT based on atomic weight was incorrect?
Before scientists knew about isotopes, they thought each element had a single atomic weight. However, when they discovered isotopes—different versions of the same element with varying numbers of neutrons—they realized that elements can exist in different forms with slightly different atomic weights. This discovery explained why the order of elements based solely on atomic weights was not always accurate, as elements with isotopes could have slightly different masses affecting their positions in the periodic table.
Modern PT vs Mendeleev:
- Modern PT has noble gases, Md’s doesn’t bc they weren’t completely discovered.
- Modern PT is arranged in order of atomic number, Md’s table was arranged in order of atomic weight, bc protons hadn’t been discovered yet.
Why is it wrong for Mendeleev to have ordered the PT in order of atomic weight.
Because elements were then put in the wrong groups.
Students should be able to relate size and scale of atoms to objects in the physical world.
Can you do this?
Yes ? Good
No ? Practice
Explain how testing a prediction can support or refute a new scientific idea.
Testing a prediction can either support or refute a new scientific idea by comparing the expected outcome (prediction) with the actual outcome of experiments.
If the experimental results match the prediction, it provides evidence in favor of the idea.
Conversely, if the results do not align with the prediction, it indicates that the idea may need revision or could be incorrect.
What is Group 0 called?
The Noble gases.
Were the noble gases included in D Mendeleev’s periodic table?
No, they hadn’t been discovered yet.
Explain the reactivity of noble gases (3 marks)
- Very unreactive
- Bc full outer energy level
- So stable
Are the boiling points of noble gases higher or lower than room temperature.
Lower, which is why they are gases at room temp.
Describe the boiling point of noble gases, Group , as you move down.
Bp increases (as relative atomic mass increases), as you move down the group.
Where are metals and non-metals found on the periodic table?
Metals on LEFT of stepped-line OR, left to bottom
Non-metals on RIGHT of stepped-line OR right to top
What type of element makes up majority of the periodic table, metals or non metals?
Metals.
Group 1 and 2 metals are very reactive and transition metals are less reactive, true or false?
True.
What happens when metals react?
4 marks
They LOSE electrons (1) to have a full outer energy level (1) in order to achieve the stable electronic structure of a noble gas (1)
By doing this they form a POSITIVE ion (1)
How many electrons do noble gases have on their outermost shell?
8, except for helium which only has two electrons on their outermost shell.
What are group 1 metals called?
Alkali metals
How many electrons are on the outermost energy level of group 1 metals?
1 electron.
Are group 1 metals soft or hard?
Soft - making them malleable.
How do group 1 metals react with oxygen.
- Very rapidly to form a metal oxide.
- G1 metal donates 1 electron from its outer most shell to oxygen which is in group 6.
- G1 metal becomes stable, but oxygen isn’t
- So another of the same G1 metal donates its outermost electron oxygen.
- That atom and oxygen are now stable.
Here’s the equation
4x + O2 -> 2x2O
where x is the group 1 metal
eg 4Li + O2 ->2Li2O
ions formed: G1 metal forms +1 ion, O2 forms oxide -2 ion
be sure to notice which is big and which is the small the coefficient and which is the subscript.
How do group 1 metals react with chlorine.
- Very rapidly.
- They donate their outer electron to the chlorine atom, which is in group 7 to form a stable +1 ion and chlorine forms a stable chloride -1 ion
Here’s the equation
2x + Cl2 -> 2xCl
insert the metal.
How do group 1 metals react with water
- Very rapidly
- A gas is produced (this is detected by effervescence)
- An alkaline solution of metal hydroxide is produced (this can be shown in universal indicator turning purple).
Here’s the equation
2x(s) + 2H2O (l) -> 2xOH (aq) + H2 (g)
insert metal - take note of state symbols
Describe and explain the trend in reactivity of group 1 metals as you go down the group.
- Reactivity increases as you go down the group.
- This is because the radius of the atoms of each metal increases bc the atomic number increases, so more electrons.
- This means there’s a greater distance between the nucleus and the outermost electron resulting in there being a lower attraction between outer electron and nucleus.
- Another reason is shielding - shielding increases as you go down the group; the outer electron faces more repulsion as you decrease down the group bc more electrons in internal energy levels, this decreases attraction between outer electron and nucleus.
Summary
- More reactive as you go down bc of increased distance and shielding.
What are group 7 elements known as?
Halogens.
Are group 7 elements metals or non-metals and what type of ion do they form?
Non-metals, so gain 1 electron to form a negative -1 ion.
How many electrons do group 7 metals have on their outermost shell?
7 electrons.
True or false, group 7 elements are diatomic?
True
Explain why group 7 elements are diatomic?
- Each G7 element has 7 electrons on their outermost shell
- So they react together by covalently bonding to share 1 electron each from their outermost shell (see image).
- They do this by overlapping their outermost shells
- This can be represented using the chemical symbols and placing a stick in between to represent a covalent bond, eg F - F meaning F2.
Describe the melting and boiling point of group 7 elements as you decrease down the group.
Melting point and boiling point increases as you go down the group.
more IMF between electrons and positive nucleus.
In group 7, which elements are gases?
Fluorine and Chlorine.
In group 7, which elements are liquid?
Bromine.
In group 7, which elements are solids?
Iodine
If the melting point is lower than 20 deg celc and boiling point is lower than 20 deg celc, what is the state of the element?
Gas
If the melting point is lower than 20 deg celc and the boiling point is higher than 20 deg celc, what is the state of the element?
Liquid
If the melting point is higher than 20 deg celc and the boiling point is higher than 20 deg celc, what is the state of the element?
Solid
Group 7 elements form what type of bonds with non-metals?
Covalent bonds.
- overlap outermost shells
Group 7 elements form what type of bonds with metals?
Ionic bonds
What happens during ionic bonding of G7 element and a metal.
- They gain one electron to become stable and achieve electronic structure of noble gas.
- So they form a -1 halide ion
Halogen ions end in -ide.
Describe the reactivity as you go down group 7
Reactivity decreases as you go down group 7
Reactivity decreases as you go down group 7, explain why.
- The radius of atom increases, so there’s a greater distance between the nucleus and the outermost electron, this means it is harder for G7 elements to attract other electrons from metals.
- Greater shielding, bc more internal electrons repel the outermost electrons and electrons from other metals, this reduces the attraction between outermost e- and electrons from metals and the nucleus.
- This makes it harder for G7 elements to attract electrons into their outermost energy level (bc less attraction to nucleus).
True or false, a more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt?
True.
eg Potassium Iodide + Chloride -> Potassium Chloride + Iodine
because chlorine is MORE reactive than iodine.
This is called a displacement reaction
Potassium Iodide + Chloride -> Potassium Chloride + Iodine
what type of reaction is this called?
A displacement reaction.
Properties of Alkali metals:
- texture (soft or hard)
- density
- melting points
- Reactivity
- Soft
- Low density
- Low melting points
- React v rapidly w O2, Cl2 and H2O
Properties of transition metals in comparison to alkali metals.
Texture (soft or hard)
Density
Melting points
Reactivity
- hard and strong
- high melting points apart from mercury which is a liquid at room temperature
- high density
- less reactive
Remember to say highER or hardER when comparing
True or false, one atom of an element of a transition metal can form ions with different charges?
True, unlike alkali metals.
True or false, transition metals can form coloured compounds?
True, unlike alkali metals
Can transition metals be used as catalysts?
Yes, unlike alkali metals
