C1 - Atomic Structure And The Periodic Table Flashcards
Information on filtration.
Filtration separates insoluble solids from liquids
Used if your project is an insoluble solid that needs to be separated
Solid impurities in the reaction mixture can be separate with filtration ‘purification’
Information on evaporation
Separates soluble solids from solutions
Solution into evaporation dish
Slowly heat solution > solvent evaporates and solution will get more concentrated > crystals will start to form
Only use if salt doesn’t decompose when heated otherwise have to use crystallisation
Information on crystallisation
Pour solution into evaporation dish and gently heat
Some solvent will evaporate and solution becomes more concentrated, once crystals start to form, leave it to cool and the salts will form crystals as it becomes insoluble in cold, concentrated solutions
Filtration and crystallisation to separate rock salt
Mixture of salt and sand, salt dissolves, sand doesn’t.
Grind mixture and make sure salt crystals are small
Pour into water and stir until salt dissolved
Filter mixture to remove sand
Evaporate water so salt forms dry crystals
Number of protons =
Number of electrons
Why do atoms have no charge
Protons and electrons charge cancel each other out
Relative mass and charge of proton, neutron and electron
Electron mass of almost 0, charge of -1
Proton mass of 1, charge is +1
Neutron mass of 1, charge is 0
What’s the atomic number
How many protons
What’s the mass number
Total number of protons and neutrons
Neutrons = atomic number - mass number
What’s an isotope
Different forms of the same elements
Same protons but different number of neutrons
E.g carbon 12 and carbon 13
What are elements
Elements consists of atoms with the same atomic number.
Each atom has a different number of protons, neutrons and electrons. The proton amount determines what atom it is
Why is there a relative atomic mass
As many elements exists as isotopes
Formula of relative atomic mass (Ar)
Relative atomic mass = sum of (isotope Abundance x isotope mass number)/ sum of abundance’s of all isotopes
Example of relative atomic mass calculation
Copper
Cu 63 abundance of 69.2%
Du 65 abundance of 30.8%
(69.2 x 63) + (30.8 x 65) / 69.2 + 30.8 = 63.6
What are compounds
Two or more atoms joined together to make a compound
Substances formed from 2 or more elements.
Atoms in fixed proportions and chemically bonded
Why is it hard to separate compounds
Because you need a chemical reaction
Properties of a compound are different to elements
Compound with metals and non-metals consist of ions
Compounds with non-metals consist of molecules
Compounds can be shown with a formula
Common compound formulas of ammonia, sodium chloride, carbon monoxide, hydrochloric acid, calcium chloride, sodium carbonate and sulphuric acid
Ammonia - NH3 Sodium chloride - NaCl Carbon monoxide - CO hydrochloric acid - HCl Calcium carbonate - CaCl2 Sodium carbonate - NaCO2 Sulphuric acid - H2SO4
What are chemical equations
Equations that show a chemical reaction
Symbol equations are shorthand
What is meant by balancing an equation
Same number of atoms on each side
John Dalton to atom
Described atoms as solid spheres
JJ Thomson on atoms
Atoms contained smaller electrons - plum puddin
Rutherford on atoms
Alpha particle scattering experiment
Fired positively charged alpha particles at gold foil - most of through
Some deflected, some changed direction kind of due to alpha particles hitting tiny nucleus
Therefore atom mostly empty space
Bohrs nuclear Model
Suggested atoms in shells - electrons orbit at fixed shells(energy levels)
James Chadwick on atoms
Provided evidence for neutrons
Where’s the lowest energy level
Closest to the nucleus - always filled first
Electronic structure of electrons
Always 2, 8, 8, 8 etc
Why is it better to have a full outer shell
So the atom doesn’t want to react to fill it - unstable
Early 1800s periodic table
Elements arranged by atomic mass - no idea on protons, neutrons or electrons
Only measure relative atomic mass
Dimitri Mendeleev’s periodic table
1869 Mendeleev took 50 known elements and arranged them and left gaps
He put in order of atomic mass but switched order if properties didn’t match
E.g iodine has a smaller mass, but placed after tellurium as it had similar properties to elements in that group
Some gaps indicated undiscovered elements
How did isotopes support mendeleev’s table
Proved not to order on relative atomic mass but to take into account properties
Isotopes have different masses but same chemical properties
Information on modern periodic table
Ordered in increasing atomic number - repeating properties
Metals on left, non-metals on right
Elements with similar properties form columns
Vertical columns form groups
What do group numbers on the period table tell you
Group number tells you how many electrons on the outer shell
Group 1 = 1 electron
Group 0 = full outer shell
This is useful as atoms react depending on number of electrons in outer shell
Rows are called…
Periods. Each new period represents another full outer shell of electrons
Information on metal elements
Metal Elements form positive ions when reacted
They’re on the bottom and left of table
Information on non-metal elements
Non-metals are far right and top
Don’t generally form positive ions when they react
Why do atoms react
To try form a full outer shell of electrons - by gaining, loosing or sharing electrons
How to metals to the left and bottom react
Left - Don’t have many electrons to remove - easier to remove electrons as there’s not as many
Bottom - more electrons but they’re further away from nucleus so feel a weaker attraction - not much energy needed to remove so it’s feasible for these elements to form positive ions
How do non-metals to the top and right react
Right - lots of electrons to remove
Top- outer electrons close to the nucleus - strong attraction
Therefore more likely to gain or share electrons so not as much energy is used to get rid of them
Properties of metals
Metallic bonding
Strong, can be bent or hammered(malleable)
Good heat + electric conductors
High boiling and melting points
Properties of non-metals
No metallic bonding Dull looking Brittle Aren’t always solid at room temperature Lower density Don’t really conduct electricity
What are group 1 metals
Alkali metals, they’re reactive soft metals
List the Alkali metals(group 1)
Lithium Li, sodium Na, potassium K, rubidium Rb, caesium Cs, francium Fr
Properties of group 1 alkali metals
1 electron in outer shell, very reactive soft and low density
Increasing reactivity as you go down - electrons further from nucleus
Lower melting and boiling points as you go down
Higher relative atomic mass as you go down
What do alkali metals form with non metals
Form ionic compounds
Group 1 don’t need much energy to lose their outer electron - readily forms 1+ ion
So easy they only ever react to form ionic compounds
Compounds generally white solids that dissolve in water to form colourless solutions
What happens when group 1 reacts with water
Vigorous reaction
Li, Na and K float, move and fizz on surface. They produce hydrogen when reacting
K and below ignite hydrogen with their energy
Group 1 reaction with oxygen
Lithium oxide
Sodium oxide or potassium peroxide
Potassium peroxide or potassium superoxide
Group 1 reaction with chlorine - what does it produce
Produces salt.
Group 1 reacts vigorously when heated in chlorine gas to form white salts and metal chlorides
Go down group = more vigorous
What are the group 7 elements
Called halogens - all non metals and coloured vapours
Group 7 coloured vapours and their reactive ness
Fluorine - very reactive, poisonous yellow gas
Chlorine - fairly reactive, poisonous dense green gas
Bromine - dense, poisonous red brown volatile liquid
Iodine - dark grey crystalline solid or purple vapour
There’s also astatine
Properties of group 7 elements
All exist as molecules which are pairs of atoms
As you go down - become less reactive as it’s harder to gain an electron - further away
Higher melting/boiling points
Higher relative atomic mass
Halogens can form…
Molecular compounds
Halogens share electrons via covalent bonding with other non-metals to achieve full outer shell
Compounds that form when halogens react with non metals all have simple molecular structures
What do halogens form with metals
Form ionic bonds
Halogens with 1- Ions are halides when they bond with metals
Compounds formed have ionic structures
More reactive halogens will displace…
Less reactive ones
Displacement reaction can happen between more reactive halogens and the salt of a less reactive one.
E.g chlorine displace bromine and iodine form an aqueous solution of its salt
Chlorine + potassium iodide -> iodine + potassium chloride
What are group elements
All inert colourless gases
Properties of group 0 elements
All eight electrons in outer (helium has 2)
Outer shell energetically stable - don’t have to give up or gain electron
Inert as they don’t react much - also non flammable
Exist as monatomic gases - single atoms NOT bonded to each other
All colourless at room temperature
As you go down, increase boiling point, increase relative atomic mass
Increase in boiling due to the number of electrons in each atom - greater inter molecule forces between them - harder to overcome
