atomic structure and the periodic table Flashcards
what are isotopes?
atoms of the same element that have a different number of neutrons
what is an example of an isotope
chloride 35 and chloride 17
what are the characteristics of chloride 35
18 neutrons
17 protons
17 electrons
abundance 75%
what are the characteristics of chloride 37
20 neutrons
17 protons
17 electrons
abundance 25%
why is the chloride on the periodic table called chloride 35.5 and not chloride 36?
the relative atomic mass is the average value for the isotopes of an element therefore
75% x 35 + 25% x 37 = 35.5
(abundance x atomic mass)
The atomic charge of of protons,neutrons and electrons (numbers)
Protons = +1 Neutron = 0 Electrons = -1
The atomic mass of protons,neutrons and electrons
Protons = 1 Neutrons = 1 Electrons = 1/2000 or negligible
what is found in the nucleus of an atom
protons and neutrons
what is found in the shells of an atom
electrons
what charge do protons,electrons and neutrons have
protons = positive electrons = negative neutron = neutral
why is an atom neutral?
Atoms are neutral because they have equal numbers of positive protons and negative electron.
what is the mass number
number of protons and neutrons
what is the atomic number
number of protons
how do you calculate the number of neutrons?
mass number - atomic number
what are the elements on the left side of the periodic table called?
alkali metals
what are the elements on the right side of the periodic table called
non metals (have intermidiate chemical properties)
what is the special name for group 7 elements
halogens
what is the special name for group 8 / 0
noble gases
what is the ‘staircase’ on the right side of the periodic table called
metaloids / semi metals
what are they called semi metals?
Because they have properties of both metals and non metals
what are the elements in the middle called
transition metals
How are the metals arranged
In increasing atomic order
Groups are …
periods are …
vertical
horizontal
what do elements in the same group have in common?
Elements in the same group have similar properties e.g group 1 and group 7 because they have the same number of electrons in the outer shell
what can the last number in an electric configuration tell you
Number of electrons in the outer shell is the group number
what can all the numbers in an electric configuration tell you
Number of shells is the period number
what is a chemical reaction
The loss or gain of electrons
what is an ion
An atom that has loss or gained electrons
Metals always …
metals always LOSE electrons to form POSITIVE ions
None metals always ….
Non metals always GAIN electrons to form NEGATIVE ions
what does the electronic configuration become of an ion?
e. g 2.8.1 to 2.8 for metals
e. g 2.8.7 to 2.8.8 for non metals
how do you write an atom as an ion?
put brackets around it and add the charge
what is the ionic symbol of a metal
+
what is the ionic symbol of a non metal
_
Example of ions
Aluminium 2.8.3 Loses 3 becomes 2.8 = Al 3+
Oxygen 2.6 gains 2 becomes 2.8 = O2-
oxidation
A chemical reaction with oxygen
Group one the alkali metals reactivity
increases as you go down
Balanced equation for lithium oxide
lithium + oxygen = lithium oxide
4 Li + O2 (small 2) = 2 Li (small 2) 2O
lithium burns with a
red flame
sodium burns with an
orange flame
potassium burns with a
lilac flame
what do the group 1 metals look like?
dull
what do group one metals look like after you cut it?
shiny
why are group one metals dull on the inside and dull on the outside?
Because the outside is the part of the metal that has been oxidised giving the dark colour,the shiny bit has not been oxidised.
why are group one metals stored in paraffin oil?
To prevent oxidisation with the oxygen in the air / prevent reaction with oxygen
what is a characteristic of the group one metals after cutting them as you go down the periods?
As you go down group one after you cut the metal the metals react quicker with oxygen / oxidise quicker
why are group one metals called the alkali metals
because when you react them they create an alkali which can be found when using universal indicator which turns it blue/purple
when lithium reacts with water what 3 things does it do?
Fizz
Float
Moves
when sodium reacts with water what 3 things does it do?
Fizz
Float
Melts into a ball
when potassium reacts with water what 3 things does it do?
Fizz
Float
Catches fire with a lilac flame
Why are lithium,sodium and potassium denser than water
Because they float and they’re less dense than 1
What gas is produced during the reaction with group one metals reacting with water?
Hydrogen gas to show there has been a reaction.
Is the reaction with group one metals and water endothermic or exothermic
exothermic - produces heat
equation for sodium reacting with water
sodium + water = sodium hydroxide
2Na + 2 H (small 2) 2O = 2NaOH + H (small 2 ) 2
what would happen if you add universal indicator to the troph of water
When universal indicator is added the water in the troph will turn blue/purple because it’s an alkali solution
what kind of molecules are the halogens
diatomic molecules (has 2 atoms)
what happens to the reactivity in group 7 as you go down
the reactivity decreases
what is the equation for when lithium reacts with chlorine
lithium + chlorine = Lithium chloride
2 Li + Cl (small 2) = 2 Li Cl
what is the equation when sodium reacts with chlorine?
sodium + chlorine = sodium chloride
2 Na + Cl (small 2) = 2NaCl
what is the equation for potassium reacting with chlorine
potassium + chlorine = potassium chlorine
what is unique about the colours of the group seven vapours as you go down the table?
The colours get darker (possibly as dark as black)
colours of the vapours group seven elements going down from fluorine
Fluorine = pale yellow Chlorine = green Bromine - orange / brown Iodine = grey / purple Astatine = black
what do the halogens give off
poisonous vapors
what is unique about the state of the halogens at room tempreture
gas to liquid to solid
what happens to the density of the halogens as you go down
increases
reaction with chlorine and iron wool
iron wool burns and glows brightly
reaction with bromine and iron wool
iron wool glows but less brightly than chlorine
reaction with iodine and iron wool
iron wool has a slight glow
equation for chlorine reacting with iron
chlorine + iron = iron (III) chloride
3Cl (small 2) + 2Fe = 2FeCl (small 3)
Iron = Fe3+
what is a flame test used for?
identifies the presence of a metal ion
flame test for lithium
red / crimson
flame test for sodium
yellow /orange
flame test for potassium
lilac
flame test for calcium
brick red
flame test for copper
blue /green
flame test for barium
Apple green
what is the silver nitrate test used for
identifies the presences of a halide ion e.g chlorine, bromide,iodide
what is the equation for silver nitrate
AgNo3 (small 3)
equation for chlorine and silver nitrate
Ag+ + Cl- = AgCl
equation for bromide and chlorine
Ag+ + Br- = AgBr
equation for iodide and chlorine
Ag+ + I- = AgI
precipitate of chlorine
white
precipitate of bromide
cream
precipitate of iodide
pale yellow
How do you detect hydrogen gas
place a lit splint and listen for a sqeaky pop
what is used in the sqeaky pop test
magnesium metal and hydrochloric acid
