C1&2 Atomic structure and Periodic Table Flashcards
What is an element
a substance with only one type of atom
What are groups
Columns in the periodic table containing elements with the same number of atoms on the outer shell
What are periods
Rows in the periodic table that contain elements with the same number of electron shells
What is an ion
an atom that has lost or gained electrons and has an overall charge
what is the atomic number of an atom
the number of protons in the atom (bottom number)
What is the mass number of an atom
The total number of protons and neutrons in the atom (top number)
what are isotopes
isotopes are different forms of the same element which have the same number of protons but different number of neutrons
What is the formula for working out the relative atomic mass of elements
sum of (isotope abundance x isotope mass number) / sum of abundance’s of all the isotopes (100)
What is a compound
compounds are make from two or more different elements combined together in fixed proportions and they’re held together by chemical bonds
What is a mixture
consists of two or more elements or compounds which are not chemically combined together
What is the method of distillation
Liquid boils off and condensed in the condenser. the thermometer will read the boiling point of the pure liquid and the vapour is cooled and condensed back to liquid and is collected
What mixture is separated by simple distillation
soluble salt dissolved in a liquid
what type of mixture is separated by crystallisation / evaporation
a soluble solid and a liquid
Evaporisation method
pour the solution into an evaporating dish and slowly heat the solution and the solvent will evaporate and the solution will get more concentrated. Crystals will form and keep heating the fish until all that is left are dry crystals
Crystallisation method
Pour solution into evaporating dish and gently heat. Once some of the solvent evaporates crystals start to form (the point of crystallisation is reached) take the dish off the heat and leave to cool. The salt should start to form crystals as it becomes insoluble in the cold, highly concentrated solution. Filter the crystals out of solution or leave in a warm place to dry
Type of mixture separated by filtration
an insoluble solid in a liquid
type of mixture separated by chromatography
a mixture of dissolved substances
Method of Chromatography
Line is drawn in pencil by the bottom of filter paper. A spot of ink is placed on the line and the sheet is placed in a beaker of solvent. Place a lid on the beaker to stop solvent evaporating. The solvent seeps you the water carrying ink with it and each different dye will move up the paper at a different rate so the dye separates and forms dots in different places. Once solvent has reached the top, dry paper.
Type of mixture separated by fractional distillation
Soluble liquids with different boiling points
Method of Fractional distillation
Mixture of liquids is heated and all liquids evaporate at different temperatures. the liquid with the lowest boiling point evaporated first and when the temperature on the thermometer reaches the boiling point it will reach the top of the column. The fractionating column has a temperature gradient so the liquids with higher boiling points might start to evaporate but will condense before they reach the cooler top. Liquid then passes through a condenser and is collected. Once first liquid has been collected you raise the temperature until the next one reaches the top
What did John Dalton do
In the 19th century John Dalton described atoms as solid spheres and said that different spheres make up different elements
What did JJ thomson conclude
Plum Pudding model theory that atoms were a ball of positive change with negative electrons embedded in it
what experiment did Ernst Rutherford and Marsden carry out? and what were his results?
They fired positively charged alpha particles at an extremely thin sheet of foil and were expecting the particles to pass straight through the foil or be slightly deflected. However although some passed through, many were deflected and a small number were deflected backwards
What did the experiments lead Rutherford to conclude?
The mass of the atom is concentrated at its centre with is positively charged and the nucleus is surrounded by a ‘cloud’ of negative electrons. When alpha particles come near the nucleus they are deflected and when they hit the nucleus they are deflected backwards
What was Niel Bohr’s theory of the atom?
Scientists realised that a ‘cloud’ of electrons would be attracted to the nucleus and cause the atom to collapse. Niel Bohr’s model suggested that electrons were contained in shells and orbit the nucleus in their fixed shells
What did later experiments of the atom and the work of James Chadwick conclude?
The idea that the positive charge of the nucleus can be subdivided into a whole number of smaller charge with each particle having the same amount of positive charge - protons. James Chadwick showed the existence of neutrons within the nucleus
How many electrons fit on each shell
First energy level - 2
Second energy level - 8
Third energy level - 8
How was the periodic table arranged before the discovery of protons, neutrons and electrons?
Scientists attempted to classify elements by arranging them in their order of atomic weights and their properties were not taken into consideration
what did Mendeleev do to the periodic table
He left gaps for elements he thought had not been discovered and in some places he changed the order based on atomic weight if the order of properties meant it should be changed. Elements with properties Mendeleev predicted were later discovered and filled the gaps.
How is the modern periodic table arranged
Isotopes of the same element have different atomic masses but same chemical properties so occupy the same position in the periodic table. Arranged in order of atomic (proton) number so that elements with similar properties are in columns known as groups. Elements in the same group (column) have the same number of electrons on their outer shell and elements in the same period have the same number of shells.
Metals are found towards the right and top of the periodic table
What happens to noble gases as you go down the group?
•Boiling points increase due to in increase in electrons which means greater intermolecular forces to overcome
Properties of group 0 (noble gases)
Full outer electron shells
Unreactive and do not easily form molecules
Properties of Group 1 (alkali metals)
- Soft
- low density (first 3 are less dense than water)
- all have one electron on outer shell
- Very reactive
What happens to alkali metals as you go down the group
- Increasing reactivity as the outer electron is further away from nucleus so weaker attraction
- Lower melting and boiling points
- Higher relative atomic mass (larger atom)
- Outer electron is lost more easily
Alkali metals reaction with water
React vigorously to produce hydrogen gas and metal hydroxides
Alkali metals reaction with chlorine
React vigorously when heated in chlorine gas to form white metal chloride salts
Alkali metals reaction with oxygen
React to form a metal oxide. This means they tarnish and a full metal oxide layer is formed in air. This is why they are stored under oil to stop them reacting with oxygen (or water) in air
Alkali Metals compared to transition metals
- Alkali metals are more reactive
- Alkali metals are less dense, strong and hard
- Alkali metals have lower melting points
Properties of group 7 - Halogens
- Have 7 electrons on outer shell
- Have coloured vapours
- Consist of molecules made up of pairs of atoms (Cl2)
- Form ionic salts with metals (-1 charge)
- Form molecular (simple covalent) compounds with other non-metallic elements
What happens to group 7 as you go down the group?
- Halogens become less reactive as it’s harder to gain an extra electron due to weaker attraction forces
- Have higher melting and boiling points
- Have higher relative atomic masses
What happens in displacement reactions
A more reactive halogen will displace a less reactive halogen from an aqueous solution of its salt.
e.g. chlorine will displace bromine and iodine for an aqueous solution of its salt
Properties of Transition metals
- Good conductors of heat and electricity
- Very dense, strong and shiny
- Do not react vigorously with water or oxygen
- Have ions with different charges
- Have coloured compounds
- Are useful as catalysts
