C1 - Atomic structure and periodic table Flashcards
Who is the best tutor?
Lucy
What is in the nucleus of an atom?
Protons and neutrons
What is the charge of a nucleus?
Positive
What is the mass and charge of a proton?
1 mass
+1 charge
What is the mass and charge of a neutron?
1 mass
0 charge
What is the mass and charge of an electron?
Very small mass
-1 charge
What is the charge of an atom?
0
What is an ion?
An atom or group of atoms that has lost or gained electrons
What does the atomic number tell you?
Number of protons
What does the atomic mass tell you?
Number of protons and neutrons
How do you find out how many neurons there are?
Mass number - atomic number
When are the number of protons and neutrons not the same?
In in ion
What decides the type of atom?
The number of protons in the nucleus
What is an element?
A substance made up of only one type of atom
What is an isotope?
Different forms of the same element, which have the same number of protons but a different number of neutrons.
What is the calculation for relative atomic mass?
relative atomic mass = sum of (isotope abundance x isotope mass number) / sum of mass abundances of all the isotopes
What is relative atomic mass?
Average mass taking into account the different masses and abundances (amounts) of all the isotopes that make up the element
What is a compound?
Substances formed from two or more elements, in fixed proportions, held together by chemical bonds.
How can a compound be separated into the original elements?
This is difficult and a chemical reaction is needed
What kind of bonding is in a compound made of a metal and a non-metal?
Ionic
What is ionic bonding?
The metal atoms lose electrons to form positive ions, and the non-metal atoms gain electrons to form negative ions. The opposite changes of the ions mean they are strongly attracted to eachother.
In compounds made up of non-metals, what type of bonding is there?
Covalent
What is covalent bonding?
Where non-metal atoms share electrons with other non-metal atoms.
What is the formula for carbon dioxide?
CO2
What is the formula for ammonia?
NH3
What is the formula for water?
H2O
What is the formula for sodium chloride?
NaCl
What is the formula for carbon monoxide?
CO
What is the formula for hydrochloric acid?
HCl
What is the formula for calcium chloride?
CaCl2
What is the formula for sodium carbonate?
Na2CO3
What is the formula for sulfuric acid?
H2SO4
What are the substances on the left hand side of a chemical equation called?
Reactants
What are the substances on the right hand side of a chemical reaction called?
Products
Are there chemical bonds between different parts of a mixture?
No
Give some examples of mixtures
Air (nitrogen, oxygen, carbon dioxide, argon)
Crude oil (mixture of different length hydrocarbon molecules)
What are the properties of a mixture?
Mixture of the properties of the separate parts. The chemical
properties of a substance aren’t affected by it being part of a mixture
Do you need a chemical reaction to separate a mixture?
No, can use physical methods
What is paper chromatography used for?
Separation of dyes in an ink
Describe the steps for paper chromatography
1) draw a line near bottom of sheet of filter paper in pencil
2) at spot of ink to the line and place the sheet in a beaker of solvent (solvent depends on what is being tested). make sure ink doesn’t touch the solvent
3) place lid on top of container to stop solvent evaporating
4) solvent will creep up paper and carry the ink
5) each dye in the ink will move up the paper at a different rate and form a different spot
6) insoluble dyes will stay on baseline
7) when solvent is nearly at the top of the paper, take it out to dry
8) end result is called a chromatogram
Why would you use filtration?
To separate insoluble solids from liquids
Or it may be used in purification (solid impurities in the reaction mixture)
What are the two ways to separate soluble solids from solutions?
Evaporation and crystallisation
Describe the steps of evaporation to separate soluble solids from solutions
1) pour the solution into an evaporating dish
2) slowly heat the solution and the solvent will evaporate, the solution will get more concentrated, and crystals will start to form
3) keep heating until all you have left is dry crystals
When would you use crystallisation over evaporation?
When the soluble salt in the solution decomposes (breaks down) when it’s heated
Describe the steps of crystallisation
1) pour solution into an evaporating dish and gently heat the solution. some of the solvent will evaporate and the solution will get more concentrated
2) once some solvent has evaporated / when you see the crystals start to form (point of crystallisation), remove the dish from heat and leave the solution to cool
3) salt should start to form crystals as it becomes insoluble in the cold, highly concentrated solution
4) filter the crystals out of solution and leave in a warm
place to dry (could also use a drying oven or a desiccator)
What is rock salt?
Mixture of salt and sand
How do you separate rock salt? (or any mixture made of up of an insoluble solid and a soluble solid)
1) grind the mixture to make sure salt crystals are small and dissolve easily
2) put mixture in water and stir - salt will dissolve but sand won’t
3) filter the mixture, grains of sand won’t fit though the holes in the filter paper and will collect on paper. sand will pass through filter paper as part of solution.
4) evaporate the water from the salt so it forms dry crystals (could also use crystallisation)
What is simple distillation used for?
Separating out mixtures that contain liquids - it separates out the solutions
Describe the steps of simple distillation
1) solution is heated, and the part of the solution with the lowest boiling point evaporates first
2) vapour is cooled, condenses and is collected
3) the rest of the solution is left behind in the flask
What are the limitations of simple distillation?
Can only separate things with very different boiling points
What method of separation would you use for a mixture of liquids with very similar boiling points?
Fractional distillation
What happens if you do simple distillation with a mixture of liquids with very similar boiling points?
If the temperature goes above the boiling point of the substance with the highest boiling point, they will both evaporate and mix again
Describe the steps of fractional distillation
1) put mixture into a flask and stick a fractionating column on top, heat it
2) different liquids will all have different boiling points so will evaporate at different temperatures
3) liquid with lowest boiling point evaporates first, when the thermometer matches the boiling point of the liquid it will reach the top of the column
4) liquids with higher boiling points may also start to evaporate, but the column is cooler towards the top. so they will only get part of the way up before condensing and running back down towards the flask
5) when the first liquid has been collected, raise the temperate until the next one reaches the top
What is an example of what fractional distillation used for?
Separation of crude oil
Describe the history of the atom
1) John Dalton - described it as a solid sphere. thought different spheres made up different elements
2) J J Thompson - plum pudding model, positively charged pudding with negatively charged electrons
3) Rutherford - did alpha particle scattering experiments (fired positively charged alpha particles at a thin sheet of gold). because the particles were more deflected than expected (and some were backwards) the plum pudding model couldn’t be right. came up with nuclear model of the atom with the electrons in a cloud
4) Bohr realised a cloud of electrons would be attracted to a nucleus and therefore atom would collapse, therefore the electrons must be orbiting the nucleus in fixed shells
Which energy level is filled first?
The lowest one
How many electrons can go in each shell?
2, 8, 8 etc
How were elements originally arranged in the periodic table?
Atomic weight
How is the period table set out now?
In orders of increasing atomic (proton) number
What does arranging elements in atomic number mean
They are repeating patterns in the properties in the elements
How can you find elements with similar properties?
Look in the same column
What does the group number in the periodic table tell you?
The number of electrons in the outer shell
What is a row called in the periodic table and what does it represent?
A period and it represents another full outer shell of electrons
What kind of ions do metals form when they react?
Positive
Why do atoms react?
To form a full outer shell of electrons
Why do metals get more reactive going down the periodic table?
Outer electrons are a long way away from the nucleus so feel a weaker attraction, and therefore not much energy is needed to remove the electrons
Why do non-metals reactivity decrease going down the periodic table?
The more you go down the table, there is more electron shells and therefore there is a long distance between the outermost shell and the nucleus. Therefore harder to attract an electron as greater energy is needed
What are the physical properties of a metal?
Strong
Malleable
Good conductor of heat
Good conductor of electricity
High melting point
High boiling point
What are the physical properties of a non-metal?
Dull-looking
Brittle
Aren’t always solid at room temperate
Don’t usually conduct electricity
Often have a lower density
How many electrons do group 1 metals have in their outermost shell?
1
Properties of alkali metals
Soft and have low density ( first 3 are less dense than water )
Trend of alkali metals going down the group?
Increasing reactivity
Lower melting and boiling points
Higher relative atomic mass
What do compounds made up of metals and non-metals look like? What kind of bonding is this?
Usually white solids that dissolve in water to form colourless solutions.
Ionic bonding
What are the products when you react water with group 1 metals?
Metal hydroxide and hydrogen
For example, if it is sodium with water, you will get sodium hydroxide and hydrogen
What are the products when you react group 1 metals with chlorine?
Metal chloride salts
For example - react sodium with chlorine to get sodium chloride
What are the products when you react group 1 metals with oxygen?
Metal oxides
For example - react lithium with oxygen to get lithium oxide
What are the elements in group 1 called?
Alkali metals
What are the elements in group 7 called?
Halogens
Properties of fluorine?
Very reactive
Poisonous
Yellow gas
Properties of chlorine?
Fairly reactive
Poisonous
Dense green gas
Properties of bromine?
Dense
Poisonous
Red-brown volatile liquid
Properties of iodine?
Dark grey crystalline solid
or
Purple vapour
How do all halogens exist in an atomic form?
Molecules which are pairs of atoms
What is the trend going down group 7?
Less reactive
Higher melting and boiling points
Higher relative atomic masses
What kind of bonds to halogens form?
Covalent with non-metals and ionic with metals
What kind of ions do halogens form in ionic bonding?
Negative
When will a displacement reaction occur?
Between a more reactive halogen and the salt of a less reactive one
How can you tell if a displacement reaction has occurred?
The colour of the products will be different to the reactants, depending on the halogens in the solution
What are group 0 elements called?
Noble gases
Properties of noble gases?
Inert, colourless gases
How do group 0 elements exist in atomic form?
Monatomic gases (single atoms not bonded to each other)
What are the trends in group 0 going down the periodic table? And why?
Higher boiling points. This is due to the increase in number of electrons, and therefore greater intermolecular forces between them which need to be overcome
