topic 1 atomic structure Flashcards
what are group 0 elements known as
noble gases
what kind of gases are noble gases at room temp
colourless gases
how many electrons do group 0 or noble gases have on their outer shell
8, a full outer shell- which makes them very unreactive
as noble gases are very unreactive, where are some reactions carried out
in the atmosphere that only contains a noble gas instead of air
what happens to the relative atomic masses of group 0 elements as you go down the group and to the boiling and melting poin
it increases
if an atom has more electrons what does it mean
it means it has a stronger force and a higher boiling and melting point
what are group 7 elements known as
halogens
the halogens form molecules that contain how many atoms
2 atoms such as Cl2
as you go down group 7, what happens
- they become less reactive- its harder to gain an extra electron as the outer shell is further from the nucleus
- have a higher melting and boiling point
what type of compounds do halogen (group 7) make
molecular compounds
what bond does halogens form
covalent bonds as they react with non-metals to gain an extra electron
how are halides formed
when halogen atoms bond with metals (ionic bonding)
a more reactive halogen will ,,,
displace a less reactive halide
what are group 1 elements known as
alkali metals
give 3 properties of alkali (group 1) metals
soft
- light
- have a low density
as you go down the reactivity series of group 1 what happens
- reactivity increases- the outer electron is more easily lost as it gets further from the nucleus. That’s because it is less attracted to the neclus
- melting and boiling points get lower
- relative atomic mass increases
group 1 alkali metals become what type of ions
1+ ions as they lose one electron on their outer shell to form an full shell
finish the equation
“alkali metal+water —->”
metal hydroxide and hydrogen
what happens when alkali metals are reacted with water
-the reactions are vigorous and produce a metal hydroxide and hydrogen gas
as you go down the in the group of alkali metals what happens to the reactions
the more violent the reaction is because the metal is more reactive
what happens when group 1 metals are heated in chlorine gas
they act vigorously and form white salts called metal chlorides
finish the equation
“alkali metal+chlorine —->”
metal chloride
when group 1 elements are reacted with oxygen what do they form
metal oxide
as group 1 metals are shiny and they become a dull grey colour once reacted with oxygen, why does this happen
because a layer of metal oxide is formed on the surface
what type of ions do metals form when they react
positive ions
what type of ions do non-metals produce
negative ions
if atoms have a full outer shell, what does it mean
it means that they are more stable
what properties do metals have (3)
- they are strong (hard to break) but can be bent or hammered into different shapes (malleable)
- great at conducting heat or electricity
- high melting and boiling points
what properties do non-metals have (5)
- dull looking
- more brittle so break easily if you bend it
- not always solids at room temp
- don’ always conduct electricity
- have a low density
in the 1800s how were elements arranged
by atomic mass
as some elements were in order of atomic mass in the 1800s what did it mean for some elements
they were in the wrong group
what did Demitri Menddeleev do in 1869
- ordered them by atomic mass
- put the elements with similar properties in the same group
- some gaps were left for elements that hadn’t been found yet so Mendeleev used them to predict the properties of these elements
what was discovered after Mendeleev made his table of elements
isotopes but they have the same position on the periodic table
how many elements are there
100
how are elements laid out in the periodic table
in order of increasing atomic number
the group number of an atom tells you what
how many electrons it has on its outer shell
the rows (periods) tell you what about an atom
how many shells it has
what do electrons move on
shells or energy levels
what was the plum pudding model
it showed the atom as a ball of positive charge with electrons scattered in this ball
to test out the plum pudding model what type of experiment did scientists carry out
alpha particle scattering experiments
what was the alpha particle scattering experiment and what did scientists do
-they fired positively charged alpha particles at a very thin sheet of gold
they expected some particles to go through the sheet and some to change direction by a small amount
why was the plum pudding model wrong the whole time
because when scientists fired the particles, they changed direction more than expected and some even went backwards
what was the nuclear model of the atom (3) this was after the plum pudding experiment
- there’s a tiny, positively charged nucleus at the centre of the atom
- most of the mass is in the nucleus
- the nucleus is surrounded by a “cloud” of negative electrons
what did Niels Bohr suggest about the nuclear model of the atom
-suggested that the electrons orbit (go around) the nucleus in shells
-each shell is a fixed distance from the nucleus
(and he was correct)
what did the experiments carried out by James Chadwick suggest
-that the nucleus contained neutral particles(neutrons)
what do mixtures contain
at least 2 different elements or compounds
what is air a mixture of
gases, mainly nitrogen, oxygen, carbon dioxide and argon
what is crude oil a mixture of
different length hydrocarbon molecules
how can different parts of a mixture be separated out by
- filtration
- simple or fractional distillation
- chromatography and more
what forms when 2 or more elements react
they form compounds
what are compounds
substances that contain atoms of different elements
what are atoms in compounds held together by
chemical bonds
what is an element
a substance made up of atoms that all have the same number of protons in their nucleus
what are isotopes
atoms with the same number of protons but a different number of neutrons- so they have the same atomic number but different mass number
what is the formula for the relative atomic mass of a number
sum of (isotope abundance x isotope mass number
————————————————————————–
sum of all the isotopes
what is the atomic number
number of protons and electrons
what is the mass number
number of electrons
how do you work out the number of neutrons
mass number - atomic number
in a positive ion: number of electrons =
atomic number - charge
in a negative ion: number of electrons =
atomic number +charge
How ate compounds formed
When elements react, atoms combine with each other to form compounds
group 0 elements act as …. gases
monatomic- single atoms not bonded together
what gases are group 0 elements at room temp
colourless gases
what happens to the boiling point as you go down group 0
it increases
why does the boiling point increase as you o down group 0
because there is an increase in number of electrons leading to greater intermolecular forces between them
fluorine is a very reactive. poisonous
yellow gas
chlorine is a fairly reactive. poisonous ….
dense green gas
bromine is a dense, poisonous
red-brown volatile liquid
iodine is a
dark- grey crystalline solid or a purple vapour
the halogens all exist as m…
molecules
what bonds do halogens form
covalent bonds because they bond with non-metals
but what do halogens form ionic bonds with
metals
what happens when alkali metals dissolve in water
they are often white solids that form colourless solutions
what do alkali metals produce
hydrogen
as you go down group one, what happens to the reaction between chlorine
it gets more vigorous
what do group 1 metals form when reacted with oxygen
metal oxide
what ions do metals form, positive or negative
positive
what bonds do all metals have
metallic bonds
how are elements laid out in the periodic table
by increasing atomic number
how were elements set out in the early 1800s
by atomic mass
why did mendeleev leave gaps in the periodic table
to predict the properties of unknown elements
what are compounds
substances formed from 2 or more elements
how are atoms held together in compounds
by chemical bonds
a compound that is formed from a metal and a non-metals consists of what
ions
a compound formed from non-metals consists of what
molecules
