Topic 1 - Atomic Structure And The Periodic Table Flashcards
What is a compound?
When an atom is chemically combined with another atom to make a compound
What are the four key features of a chemical reaction?
- compounds are broken up or formed
- at least one new substance is formed
- there is a measurable energy change
- no atoms are created or destroyed
What are mixtures?
2+ substances that haven’t been combined chemically and can be separated
Do the chemical properties change in mixtures?
No
What does chromatography separate?
Solutions with a number of different solutes (solids) in the solvent (liquid)
What does filtration separate?
Mixtures that contain insoluble solids and liquids
What does crystallisation separate?
Solutions into their separate parts (dissolved solids and liquids)
What does fractional distillation separate?
Lots of liquids with different boiling points
What does simple distillation separate?
Two liquids with different boiling points
How does simple distillation work?
1) The mixture is heated until the liquid with the lower boiling point starts to boil
2) the vapour released passes through a condenser, where the gas cools back into a liquid
Why is a thermometer used in simple distillation?
To make sure the highest boiling point isn’t exceeded otherwise both liquids would boil and the process would not separate them
What did John Dalton describe atoms as?
Solid spheres
What did JJ Thompson discover?
Electrons and came up with the ‘plum pudding model’ which shows atoms as a ball of positive charge with electrons stuck in it
What experiment did Ernest Rutherford do?
The alpha particle scattering experiment - he fired positively charged alpha particles at a thin sheet of gold
What conclusion did Ernest Rutherford reach?
The mass of an atom was concentrated in the centre and has positively charged protons
What atomic model did Rutherford come up with?
The nuclear model
What did Bohr discover?
Electrons orbit the nucleus at fixed distances
Who discovered neutrons?
James Chadwick
What is an element’s atomic number?
How many protons it has
What is an element’s mass number?
The total number of protons and neutrons
What are isotopes?
Atoms of the same element with the same number of protons but a different number of neutrons
What is a relative atomic mass?
The average mass of all of the isotopes of an element
What are elements on the periodic table organised by?
In order of their atomic number (how many protons they have). Every time you move an element to the right, the proton number increases by 1
Why do elements in the same column/group react in similar ways?
They have the same number of electrons on their outer shell
How did John Newlands organise the periodic table?
It was ordered by the mass of an element but the table was incomplete and some elements were placed in inappropriate groups
What did Mendeleev do to the periodic table?
He recognised that there may be many undiscovered elements so added gaps to account for them. He also predicted the properties and masses of the undiscovered elements.
- he put elements in order of relative atomic mass
Where are metals found on the periodic table?
The left because they have few electrons on their outer shell
Properties of metals:
High melting and boiling point
Solid @ room temperature
Good conductors of heat and electricity
Where are non-metals found on the periodic table?
The right hand side because they have many electrons on their outer shell
Properties of non-metals:
Low melting and boiling points
Normally found as gases
Generally do not conduct heat or electricity
Where are noble gases found?
In group 0
Properties of noble gases:
Unreactive because they have a full outer shell already
Can be used in light bulbs as don’t react with the hot metal filament
Low boiling point
Low density
What does it mean by ‘noble gases are monatomic’
Noble gases exist as single atoms instead of forming molecules because they are unreactive
What happens to the boiling point of noble gases as you go down the periodic table?
The boiling point increases
Due to the number of electrons increasing meaning there are greater intermolecular forces
What happens to the density of noble gases as you go down the group?
It increases because of the increasing relative atomic mass.
Low density makes them useful for balloons
Where are halogens found?
Group 7
Properties of halogens:
- very reactive because they easily accept an electron into the outer shell
- form negative ions
- diatomic molecules
What happens to the reactivity of halogens as you move down the periodic table?
It decreases because the distance between the outer electron shell and the nucleus increases so the attraction between the nucleus and the electron (to be gained from another element) decreases
What can happen to less reactive halogens?
They can be displaced by more reactive halogens from compounds
What are the elements found in group one referred to as?
Alkali metals
What happens to the reactivity of alkali metals as you move down the periodic table?
It increases because the distance between the outer electron and the nucleus increases meaning there is a weaker force of attraction between them and it’s easier for an electron to be lost
How do group one metals react with water?
The metal floats on the surface and melts to create a metal hydroxide. The energy released in fed reaction is enough to melt the metal
How do group one metals react with chlorine?
A metal chloride is formed which dissolves in water to give a colourless solution
How do group one metals react with oxygen?
The metal rapidly turns from silvery/shiny to dull as a metal oxide is produced
Where are transition metals found?
In the middle of the periodic table
Relative to the alkali metals what are the properties of transition metals:
- higher density
- greater strength and hardness
- lower reactivity
- higher melting points
- can be used as catalysts
