Atomic Structure Flashcards
what is an atom?
smallest part of an element that can exist, they make up everything
what is an atom made up of?
proton - +1, 1 mu
neutron - 0, 1 mu
electron - -1, 1/2000 mu
how are subatomic particles distributed?
neutrons and protons are stored in the nucleus which is positive and contains most of the atom’s mass
electrons orbit the nucleus in fixed positions in shells, following the 2.8.8 rule
what is an element?
a substance made up of one type of atom
what is a compound?
a substance made up of two or more different elements chemically combined
what is a mixture?
a substance that contains tow or more elements and/or compounds that aren’t chemically combined
how can you separate mixtures?
chromatography
filtration
crystallisation
distillation
fractional distillation
when is chromatography used?
to separate a mixture of liquids (inks) using a stationary phase
when is filtration used?
to separate insoluble solids from liquids
when is crystallisation used?
to separate a mixture of a dissolved solid from a liquid with heat
when is distillation used?
to separate two liquids with different boiling points using heat and condensation
when is fractional distillation used?
to separate a mixture of liquids with different boiling points using heat, condensation and fractionating tower
what is the atomic mass of an atom?
the number above the chemical symbol + the sum of protons and neutrons in an atom
what is the atomic number if an atom?
the number under the chemical symbol + the number of protons/electrons in an atom
how do you find the number of neutrons in an atom?
atomic mass - atomic number
what is an isotope?
atoms of the same element with the same number of protons but a different number
of neutrons
what is relative atomic mass (RAM)?
the average mass of all the different isotopes of an atom
RAM equation
(atomic mass x percentage)+(atomic mass x percentage)/100
what is an ion?
a charged atom
cation - positive
anion - negative
development of atom model
19th century - John Dalton = atoms = solid spheres + different spheres = different elements
1897 - J J Thompson = plum pudding model = ball of positive charge with electrons embedded in it
1909 - Ernest Rutherford = alpha particle scattering experiment = positively charged alpha particles fired at thin sheet of gold = most passed through atom + some were deflected + others deflected backwards = plum pudding wrong = mass concentrated in positive nucleus + cloud of negative electrons + atom is empty space
Niels Bohr = electrons orbit in fixed shells + discovered protons
James Chadwick = neutrons
how are elements arranged in the periodic table?
by their properties (physical and chemical)
atomic mass
metals = right non metals= left
rows = periods = no. of shells
columns = groups = elements with similar properties
how did Dmitri Mendeleev change the periodic?
1869 - rearranged periodic table and left gaps
elements were mainly arranged in order of atomic mass but some were switched due to their properties
gaps = elements with similar properties in same group + existence of undiscovered elements
how are metals and non-metals different?
metals
- strong
- malleable
- conductors
- high melting/boiling points
- lustrous
non-metals
- dull
- brittle
- usually not solids at room temp
- aren’t really conductors
- lower density
group 0 (noble gases) properties
- full outershell = inert/unreactive
- monatomic
- colourless gases at room temp
- non-flammable
- boiling/melting points
increases as you go down the
group - low melting/boiling points
- glow brightly when high voltage
electricity pass through them
eg. neon lights
group 1 ( alkali metals) properties
- very reactive
- soft
- low density
- reactivity increases + lower
melting/boiling points as you
go down the group
reaction with water - react vigorously = hydrogen
gas released + metal hydroxide
produced
reaction with chlorine - react vigorously = white metal
chloride salts produced
reaction with oxygen - metal oxide formed
group 7 (halogens) properties
- coloured vapours
- diatomic
- less reactive +higher
melting/boiling points as you
go down the group
transition metal properties
- conductors
- very dense
- strong
- shiny
- form more than ion = colourful
eg. copper sulfate - good catalysts = iron for Haber
process = ammonia
transition metals vs alkali metals - 6 marker example 6/6
transition metals are strong, shiny and good conductors similar to ‘proper’ metals. transition metals can form multiple ions whereas alkali metals can only form a positive ion. transition metals have much higher points than group 1 metals. alkali metals are soft and some such as potassium can float on water however transition metals like nickel are much harder and sink in water. transition metals don’t react as vigorously with water, oxygen and group 7 elements for example, sodium reacts vigorously with water and produces a flame but manganese doesn’t react with water at room temp
