C1 - Atomic structure & The Periodic Table Flashcards
What is an Element?
A substance where all of the atoms are the same (made of one type of atom)
What is a compound?
A substance made up of two or more different elements chemically combined in fixed proportions.
What is a mixture?
2 or more elements or compounds that are not chemically combined.
What is a molecule?
Any elements chemically combined even if they’re the same element
What are the 2 stages of simple distillation
- Evaporate the liquid by heating.
- Condense the vapour back to a liquid by cooling.
In Chromatography, what is the stationary phase (1), and the mobile phase (2)?
- Paper - It does not move.
- Solvent - moves up the paper.
What does a pure compound (1) and a compound in a mixture (2) look like when chromatography has taken place?
1) Singular spot in all solvents.
2) Separate into different spots depending on the solvent.
Why do we draw the starting line in pencil when carrying out chromatography?
If we drew the line in pen, the pen ink could dissolve in the solvent and move up the paper.
Filtration:
Used to separate an insoluble solid from a liquid.
Mixture poured through filter paper.
Crystallisation:
Used to separate a soluble solid from a liquid.
If left for a few days, liquid evaporates & leaves behind the soluble solid.
Gently heating the solution speeds up the process.
Fractional distillation is used to…
Separate a mixture of different liquids.
Describe how the results of the alpha scattering experiment lead to the nuclear model
Alpha particles (with positive charge) fired at gold foil.
Pass straight through - Atoms are mainly empty space.
Deflected - Centre of atom (nucleus) has positive charge.
Bounce back - Centre of atom (nucleus) contains a great deal of mass.
Modification of nuclear model: Discovery of electron energy levels
Bohr proposed that electrons orbit the nucleus at specific distances
Modification of nuclear model: The proton
Positive charge in nucleus is due to tiny positive particles called protons
Modification of nuclear model: The neutron
Chadwick discovered the nucleus also contains neutral particles called neutrons
Radius of an atom:
0.1 nanometres
1 x 10^-10 m
Radius of the nucleus:
1 x 10^-14 m
Relative charges of Proton, Neutron & Electron
Proton: +1
Neutron: 0
Electron: -1
Relative mass of Proton, Neutron & Electron
Proton: 1
Neutron: 1
Electron: Very Small
Define Atomic number & Mass number
Atomic number - Number of protons & electrons
Mass number - Number of protons & Neutrons
Mass number - Atomic number = Number of Neutrons
Atoms of the same element have:
Same number of protons.
However number of neutrons is not fixed.
Define Isotopes
Atoms of the same element with different numbers of neutrons
Define Ions
Atoms which have an overall charge.
(They have lost or gained electrons)
Describe Relative atomic mass
An average that takes account of the abundance of the isotopes of the element.
Relative atomic mass equation:
(Mass no. of isotope 1 x percent abundance of isotope 1) + (mass no. of isotope 2 x percent abundance of isotope 2)
________________________________________
100
Describe early attempts to arrange the elements into a periodic table
Arranging elements in order of their atomic weights.
Newlands “Law of octaves”:
In order of increasing atomic weight.
Every 8th element reacts in a similar way.
Explain why Mendeleev’s periodic table successfully predicted the properties of elements
• Arranged elements in order of increasing atomic weight.
• If needed, he switched the order of specific elements to for the patterns of other elements in the same group.
• Realised that some elements had not been discovered - left gaps where he thought an element was missing.
• Predicted the properties of undiscovered elements based on other elements in the same groups.
How are elements arranged in a modern periodic table
• Arranged in order of atomic number
• Group 0: noble gases
Why are group 0 elements unreactive?
They have a full outer shell, so they are stable.
This means they won’t react.
How do the boiling points of group 0 elements vary down the group?
The boiling point increases as you go down the group.
Where are metals & non-metals positioned on the periodic table?
• Metals are found to the left and towards the bottom
• Non-metals are found towards the right and top
Describe how metals react to form positive ions
• They lose electrons to achieve a full outer shell
• This gives them the stable electronic structure of a group 0 noble gas.
*Metals always form positive ions
Group 1 metals reaction with oxygen
2 metal atoms transfer their outer electrons to oxygen.
2 metal ions are formed & an oxide ion is formed.
A metal oxide is formed
Group 1 metals reaction with chlorine
Metal atom & chlorine atom react.
Metal ion & chlorine ion is made.
A metal chloride is formed.
Group 1 metals reaction with water
• The metal reacts rapidly & there is effervescence - tells us that a gas is being produced.
• Alkaline solution is made.
Explain why group 1 metals reaction more rapidly as we move down the group
• Outer electrons are more easily lost.
• This is because there is a greater distance between positive nucleus & negative outer electron.
• As this distance increases, the outer electron is less attracted to the positive nucleus
• Outer electron is repelled by electrons in the internal energy levels (shielding) - decreases the attraction between the nucleus and outer electron
• Shielding increases as we move down group 1 as elements have more electrons in internal energy levels.
Describe how group 7 elements consist of molecules with 2 atoms
2 atoms of a group 7 element react and share a pair of electrons to form a covalent bond.
Group 7 molecule is produced.
Describe how melting and boiling points of group 7 elements change down the group
The melting & boiling points increase as we move down group 7
Describe how group 7 elements form covalent compounds when they react with non-metals
Both elements require 1 extra electron so they form a covalent bond.
A covalent compound is formed.
Describe how group 7 elements form Ionic compounds when they react with metals
When a halogen atom reacts with a metal atom, the halogen gains 1 electron.
The extra electron gives the halogen an overall charge of -1 (Chloride ion)
Describe & explain how the reactivity of halogens changes down group 7
•The halogens get less reactive as we move down group 7.
• Electrons are gained less easily as the distance between the nucleus & outer electron increases.
• Greater shielding of outer electron.
A (…) halogen can displace a (…) halogen from an aqueous solution of its salt
1) (more reactive)
2) (less reactive)
Describe the properties of transition elements
• Hard & strong metals.
• High melting points.
• High density
• Much less reactive than group 1 metals
• Can form ions with different charges
• Form coloured compounds
• Useful as catalysts
