1.1 Atoms Flashcards
define atoms
atoms are the smallest thing that exists
define elements
an element is a substance made up from only one type of atom
define compounds
a compound is a substance made up of two or more elements chemically combined.
define mixtures
a mixture is a substance made up of two or more elements NOT chemically combined so can be separated by physical processes
Explain the history of the atom
1800- John dalton
discovered that atoms were the smallest thing that existed
1897- j.j Thompson
discovered the ‘plum pudding model’ which was a positive-charged ball which has negative charged particles spread over it.
1911- Ernest Rutherford
discovered that there was a positive nucleus at the centre.
1913- Neils Bohr
discovered that electrons moved in orbits and the positive charge of the nucleus was made up of particles called protons.
1932- James Chadwick
discovered the neutron which is found inside the nucleus with the proton.
Give the relative charge of each subatomic particle
proton- +1
neutron- 0
electron- -1
define atomic number
atomic number = number of protons
define mass number
mass number = number of protons + number of neutrons
give the relative mass of each subatomic particle
proton- 1
neutron- 1
electron- very small (1/200)
define isotopes
isotope contains the same amount of protons but different amount of neutrons
how do you calculate:
number of protons-
number of neutrons-
number of electrons-
to calculate:
number of protons = atomic number
number of neutrons = mass number - atomic number
number of electrons = atomic number (for atoms, not ions)
define relative atomic mass
The relative atomic mass of an element is an average value that takes account of the abundance of
the isotopes of the element
formula for relative atomic mass?
relative atomic mass =
total mass of all atoms of element/ total number atoms of that element
describe the electronic structure of an atom
2,8,8,2
How are elements arranged in the periodic table?
Elements are arranged in the periodic table by:
- atomic (proton) number
- how many electrons are in their outer shell
explain the development of the periodic table
Before the discovery of protons, neutrons and electrons scientists attempted to classify which group elements belonged in with their atomic weights.
Mendeleev overcame problems with undiscovered elements and so left gaps for them to be later investigated.
how do you know if an element is non-metal or metal?`
elements that react to form positive ions are metals
elements that react to form negative ions are non-metal
where are non-metals and metals positioned in the periodic table?
non-metals are found towards the top and right.
metals are found towards the bottom and left.
Group 0 information
group 0:
- it is named the noble gases
- it is unreactive as it has a full outer shell
- their boiling points increase as you go down the group
Group 1 information
group 1:
- they are known as the alkali metals
- have a low density
- react with non-metals to form ionic compounds [these compounds are white solids which dissolve in water to form colourless solutions]
- react with water, releasing hydrogen
- form hydroxides that dissolve in water to give alkaline solutions
- the reactivity of the elements increase going down the group
Group 7 information
group 7:
- they are known as the halogens
- have 7 electrons in their outer shell
- are non-metals
- the boiling/melting point increases further down the group
- the reactivity decreases going down the group
- a more reactive halogen can displace a less reactive halogen
comparison of group 1 (alkali metals) with transition metals
similarities:
- thermal conductor
- electrical conductor
- react with non-metals to form ionic compounds
- shiny when polished
differences:
(alkali metals) (transition metals)
-low melting points -high melting points
- low density -high density
-very soft -hard
-very reactive -low reactivity
-react to form 1+ ions -react to form ions with
-compounds are white different charges
-do not act as catalysts -compounds are colour
-are often catalysts
