Atomic Structure And The Periodic Table Flashcards
What are atoms
The smallest pieces of an element that can exist
They have a radius of 1 x 10^-10 m
Radius of nucleus is 1 x 10^-14
What are compounds
Contains at least 2 different elements
Atoms of different elements combine to form compounds
What are elements
Substance of one type of atom
What are mixtures
Made up of 2 or more substances that haven’t been chemically bonded togerher
What are examples of separation techniques
Crystallisation
Chromatography
Filtration
Simple distillation
Fractional distillation
A what is crystallisation
Separates solutions into their constituent parts-dissolved solids and liquids
Heat the mixture so the solvent evaporates
Cool the solution and the solid starts to crystallise as it becomes less soluble at lower temps
What’s chromatography
Separates solutions with a number of diff solutes in the solvent
Place a piece of paper with a spot containing a mixture in beaker with solvent
Solvent level slowly rises separating the mixture into components
What’s filtration
Separated mixtures of insoluble solids and liquids. Done by pouring the mixture through filter paper because the particles are too big to fit through the paper
Filtrate is substance that comes through
What is distillation
Special technique used to separate mixtures of liquids. It used the different boiling points of liquids to separate them
What did JJ Thompson discover in 1897
Electrons
How did Jj Thompson discover electrons
He modelled it as a “plum pudding” a ball of positive charge with negatively charged electrons mixed in with the dough
What did Ernest Rutherford calculate in 1909
Discovered that alpha particles could bounce off of atoms
Concluded that an atoms mass is concentrated in its centre. Called the nucleus and contained positively charged protons
How did Ernest Rutherford discover the nucleas in 1909
A beam of alpha particles was aimed at very thin gold foil and their passage through was detected
Some of the alpha particles emerged from the fo I’ll at different angles and some came straight back
Most particles went through showing it was mostly empty space
What did Niels Bohr conclude
That electrons orbited the atom at fixed distances
Later showed positive charge of any Nucleas could be subdivided into a while number of smaller particles each having the same amount of positive charge
What did James Chadwick discover in 1932
That some particles in the nucleus had no charge at all. He called them neutrons
What are the three different subatomic particles
Protons
Neutrons
Electrons
What is the info about protons
Relative charge of +1
Found in the nucleus
Relative mass of 1
What is the information about neutrons
Neutrons have no charge
Found in the nucleus
Relative mass of 1
What is the information on electrons
Relative charge of -1
Found in fixed orbits around the nucleus
Very small mass
How do you find the number of protons and electrons in an atom
By identifying the atomic number which is the bottom number
How do you find the number of neutrons in an atom
By subtracting the mass number (top number) from the atomic number (bottom number)
What was John newlands periodic table like
Ordered his table in order of atomic mass
Realised similar properties occurred every eighth element “law of octaves”- but broke down after calcium
The table was incomplete and some elements were placed in inappropriate groups
What was Dimitri Mendeleevs periodic table like
Ordered his table in order of atomic mass but not always strictly like in some places he changed the order based on atomic weights
Left gaps for elements that he tho if he’s had not been discovered yet
What was the outcome of mendeleevs periodic table
Knowledge of isotopes made it possible to explain why the order based on atomic weights was not always correct
What are the properties of metals
High melting and boiling points
Conductors of heat and electricity
All solids (except mercury)
React to form positive ions
What are the properties of non metals
Lower melting and boiling points
Often found as gases
Generally don’t conduct heat or electricity
Do not form positive ions
What are isotopes
The same number of protons however a different number of neutrons
What are the three isotopes of hydrogen
Protium
Deuterium
Tritium
What is the information about protium
1 proton and 0 neutrons
99.98% of hydrogen atoms are protium
Used in hydrogen fuels cells and production of plastics
What is the information about deuterium
1 proton and 1 neutron
0.02% of hydrogen atoms are deuterium
Used in nuclear fusion
What is the information about tritium
1 proton and 2 neutrons
Very very rare
Used in thermonuclear fusion weapons
What is the relative atomic mass
RAM= isotope abundance x isotope mass number / 100
What are noble gases
The elements of group 0
For example argon or neon
What are the physical properties of noble gases
Low boiling points
The attractive forces between the atoms becomes stronger
Going down group 0 the atoms become larger
The intermolecular forces become stronger
More energy is needed to overcome those forces
What are the chemical properties of noble gases
They are inert. They are unreactive because they have a full outer shell of electrons
Te boiling points increase going down the group
Why are noble gases unreactive
When elements react, their atoms complete their outer shells by losing, gaining, or sharing electrons. Atoms of group 0 elements already have stable arrangements of electrons. This means that they have no tendency to lose, gain, or share electrons. This is why the noble gases are unreactive. It also explains why atoms of group 0 elements do not share electrons to form molecules.
What are the physical properties of halogens
7 outer electrons
Diatomic molecules-halogens share electrons to make diatonic molecules
What are the trends of halogens
The further down a group the higjer it’s melting and boiling point is
This is because
The molecules get larger
The intermolecular forces become stronger
More energy is needed to overcome those forces
What are the reactions with metals like with halogens
The halogens react with metals to produce salts. The salts are made up of ions, which are held together by ionic bonds.
What’s re the reactions like with nonmetals with halogens
The halogens react with non-metals such as hydrogen. When a halogen reacts with hydrogen, the product is a compound called a hydrogen halide.
What are the physical properties of group 1 metals
They are soft
Have relatively low melting points
Have low densities
What is the difference between the plum pudding model and the nuclei model
In plum pudding model there’s a positive sphere with negative charge randomly placed within. There is no empty space
In nucleur there is a central positive tiny nucleus with mostly empty space and lots of negative charges a long way from the nucleus
The mass in plum pudding is distributed equally throughout the sphere. The mass in the nucleus model is concentrated in the nucleus
Electrons orbit the nucleus in nucleur model
What is the relative atomic mass
An average value that takes account of the abundance of the isotopes of an element
What is the periodic table
Elements are arranged in order of atomic number and so that elements with similar properties are in columns
Elements with the same periodic group have the same amount of electrons in their outer shell giving them similar properties
What is the important of a peer review of resukts
Helps to detect false claims and establish a consensus about which claims should be regarded as valid
Scientific development in the popular media are not subject to peer review and may be oversimplified, inaccurate or biased
Properties of alkali metals
They have characteristic properties due to the single electron in their outer shell
React vigorously with water to create an alkaline solution and hydrogen
React with oxygen to form an oxide
React with chlorine to form a white precipitate
Reactivity increase going down the groip
What are all the lithium reactions
Oxygen- burns with a strong red flame and produces a white solid
Water-fizzes steadily gradually disappear
Chlorine-white powder is produced and settles on the sides of the container
What are the sodium reactions
Oxygen- strong orange flame and produces white solid
Water- fizzes rapidly, melts into ball and disappears quickly
Chlorine- burns with yellow flame, clouds of white powder produced
What are potassium reactiodn
Oxygen-large pieces produce lilac flame, smaller ones make solid immediatley
Water- ignites with sparks and a lilac flame
chlorine- reaction is more Vigourous that with sodium
Why does the reactivity decrease going down the halogen group
Halogens react by gaining an electron to increase their number of outer shell electrons. The number of shells of electrons increases going down the group so down the group the elements attracts electrons from other atoms less so can’t react as easily
This means that a more reactive halogen can displace a less reactive halogen in an aqueous solution of salt
What is simple distillation
Separates liquid from a solution
Solution is heated The liquid boils off and condenses. Thermomètre reads the boiling point of the pure liquid
Pure water collects in a beaker
Why would an element help Mendeleev period table be accepted
Fitted in a gap
Properties were predicted correctly
Why did Mendeleev reverse the order of some pairs of elements
So properties matched the group
Why does the reactivity increase in group one metals
The outer electrons are further from the nucleus so there is less attraction between the nucleus and the electron. So the atoms lose electrons more easily so the reactivity increases
