C1 atomic structure and the periodic table Flashcards
Element
A substance that cannot be broken down chemically
Compound
A substance that contains at least two different elements chemically combined and fixed proportions
Elements
Are made up of atoms that are all the same
Compounds
Are made from atoms or charged atoms of different elements which are been chemically joined together
Mixtures
Can be easily separated because of the chemicals in them or not join together.
Mixture of separation techniques
Filtration, crystallisation, simple distillation, fractional distillation and chromatography.
Democritus
400 BC
Describe the materials has been made of small particles which could not be divided. These particles were atoms. He had no evidence
John Dalton
1803
He described an atom a billiard ball which could not be divided
J.J. Thomson
1897
Who describes atoms using a plum pudding model. The negative electrons were thought to be embedded in a ball of positive charge (protons)
Geiger and Marsden
1909
They conducted an experiment with gold leaf and alpha particles. This showed that the atom had a positively charged nucleus in the centre where most of the mass of the atom is concentrated and much of the atom was empty space
Niels Bohr
1913
He confirmed previous experiments although explained that electrons orbiting the nucleus
James Chadwick
1920
Term proton was used for positively charged atoms
1932
Neutron discovered
Atoms
Is made up of a nucleus that is surrounded by electrons
Electron shells
Electrons occupy the space around the nucleus in shells. The space between the nucleus and the electron shells is empty space.
Atomic radii
A typical atomic radius is about 0.1 nm (1×10 to the -10 m)
However the radius of an atom increases within a group of elements. The atomic radii a Li,Na,K increase as more electrons are added to the atom
The atomic number
The number of protons/ electrons in an atom
Relative atomic mass
Number of protons and neutrons
Isotopes
A form of an element that has the same number protons but different number of neutrons
Relative abundance calculation
Ar = (mass of first isotope x % Of first isotope) + (Mass of first isotope x % of first isotope) /100
Electron shell formation
2,8,8,18,18,32,32
Periodic table
The periotic table is arranged in order of proton number
Rows show how many shows how many electron shells it has
Columns show how many electrons it has and that shell
Row
Column
Period
Group
Group 1
Group 7
Group 0/8
Highly reactive metals
The halogens-react with group 1 metals to make Salts
Are are unreactive-noble gases
Döbereiner
1829
Noticed that sometimes three elements have similar properties. These were called Döbereiner triads
1860
I need a list of more accurate atomic weight was published
John Newlands
1865
Noticed that when he put elements in atomic weight order some of them seem to be in the wrong place there was often a pattern of similar properties every eight element. He called his new theory the law of octaves. He noticed the patterns but did not make predictions
Dimitri Mendeleev
1869
Decided to swap some elements around so that the patterns of chemical behaviour fitted better
was able to imagine that were undiscovered elements
Left gaps in his table for later discoveries
Put eka infront of names , 3 elements were discovered in his lifetime
Periodic table modern day
1932
Theory developed and supported with evidence- isotopes explained why order was wrong. Discovery of neutron explained why it had to be by number of protons
Physical properties of metals
Lustrous Hard High density High tensile strength High melting point and boiling point Good conductors of heat Good electrical conductor
Physical properties of nonmetals
Dull Soft, brittle, liquid or gas Low density Low or no tensile strength or gas Low melting point and boiling point Poor or no thermal conductivity Poor or non conductors of electricity
Chemical properties of metals
Result of reactions with oxygen or acids to make salts and hydrogen gas
Form basic oxides
Chemical properties of nonmetals
Result of reaction with oxygen
Eg carbon with oxygen to make CO2
Form acidic (or neutral) oxides
Metals and nonmetals in the periodic table
Metals are on the left hand side and non metals are on the right hand side
Positions of elements in the table
If it makes a positive ion it is a metal
Nonmetals make negative ions
Stable atoms
The noble gases or stable atoms as they have a full outer shell
What can happen to the electrons in the outer shell
They can be transferred to the outer shell of another atom
They can have electrons are added to the outer shell from another atom
They can be shared with another atom
Group 0
All unreactive
All gases
Why does helium stay as a gas at lower temperatures?
Exist as single atoms not molecules
The smaller the atom it is it is for them to keep moving around rapidly
Why do elements in group 0 exist as single atoms?
They do not make compounds with other elements and are unreactive. This is because they have 8 electrons in their outer shell
Properties of group 1 elements
They are less dense than water so they would float
React vigorously with water to produce hydrogen
Burn in water to form oxides (sodium)
Reaction trends of alkali metals
Lithium reacts vigorously with water
Sodium reacts very vigorously with water sometimes an orange flame produced
Potassium reacts extremely vigorously with water and produces a lilac flame
What is an ion
When an atom loses or gains an electron
Halogens
Are non metals Exist as a pair of atoms React vigorously with group 1 metals Make gases or liquids such as acids Are solid or gas at room temp
Reactivity
1 increases down group
7 increases up the group
Trends across the table
Metal to non metal
Across and down depend on atomic structure and electronic structure
Period 2&3 outer electrons increase by 1 from group 1
Group 2 with 2 outer electrons up to group 7 with 7 outer electrons
Group 1 lose electron to form +ions easier
Group 7 gain 1 electron to form ions
Transition elements
Are metals and have typical metallic properties
Found in the middle part of the periodic table
Less reactive than elements in group 1
Often catalysts
A catalyst
An element or compound that changes the rate of a chemical reaction without taking part in the reaction as a reactant. Catalysts are unchanged by the reaction.
Ions and coloured compounds
A compound that contains the transition element is often coloured
Can form 2 types of positive ions.
