Atomic Structure and Amount of substance Flashcards
Atomic number definition
The total number if protons in an atom of an element
Definition mass number
The total number of protons and neutrons in an atom of an element
What charge are cations
Positive
What charge are anions
Negative
relative atomic mass definition ;
an average mass of an element in comparison to an atom of carbon 12 mass
what is definition of relative molecular mass ;
average mass of 1 formula of that compound compared to 1 atom of carbon
relative isotopic mass definition ?
mass of an isotopic mass in comparison with 1 / 12 of the mass of an carbon 12 atom
proton , neutron and electron charges
+1 , 0 , -1
proton neutron and electron masses
1, 1, 1/1840
define an isotope
atoms of the same element with the same number of proton and electrons but different number of neutrons
define an ion
element with the same number of protons and neutrons but different number of electrons
RAM equation :
( isotope 1 mass no x % abund of iso1 ) + ( isotope 2 mass no x isotope abunance % of iso 2 ) divided by 100
order of development of the atom :
Democitrius - atoms can not be broken down into smaller particles
Aristotole - discovered 4 elements matter is made of : fire , air , earth , water
Boyle - modern version of elements
Dalton - atoms are spheric balls - cannot be created or destroyed , atoms of same element are the same and atoms of different atoms are different + created some chemical symbols
Faraday & Davey - by electrolysis discovered matter is electrical in nature
Crookes - cathod ray discovery by cathod ray tube ( eventually called electrons )
Thompson - plum pudding model +ve charge with negative electrons embedded in it
Goldstein - behind cathode rays are +ve rays emitted . type of ray depemnds on gas in tube . eventually called proton by rutherford .
Bequeral - radioactivity
Geiger and Marsden ( rutherfords students ) gold leaf experiment
Chadwick - neutrons
Bohr - protons
geiger & marsden
rutherford students discovery
most alpha particle went straight through - atoms have ;ots of empty space
some alpha particles were deflected - particles must have passed something ( nucleus )
some alpha particles were deflected right back to where they came from - hit something dense and positivly charged ( nucleus )
how to find percentage abundance of an isotope using ToF
the size of the current produced when the ion hits the detector allows us to discover the abundance of the isotope .
how to find mass of an isotope
time taken for an ion to drift down the chamber
how do elements with low formula mass become ionised :
electron impact -
the sample is vaporised
high energy e- are fired at it . They ‘knock; an electron off leaving the sample to form positive ions .
they are attracted towards a negative electron plate .
how do elements with a high formula mass become ionised :
electrospray ionisation
sample is dissolved in a volatile solvent
injected through hypodermic needle
particles become ionised by gaining protons from a solvent
produce xh ions
attract to negative plate .
what happens at ToF:
sample placed in a chamber
ionisation converts ion to +ve ions
attract to negative plate
ions accelerate - increase kinetic energy of ions
pass through -ve plate
drift down chamber to detector
once reached they gain electrons from detector
lighter the mass- faster it arrives to the detector .
molecular formula definition
actual number of atoms of each element in a compound .
empirical formula definition
simplest whole number ratio of atoms of each element present in a compound .
number of particles - equation
amount ( moles ) x Avogadro’s constant
amount in moles - equation
mass in (g) divided by molar mass
what is a solute ?
something that is dissolving
what is a solvent ?
what the solute is dissolving in
what is a solution ?
what it makes
what does concentrated mean ?
a lot of solute per dm3
what does dilited mean ?
a small amount of solute per dm3
concentration equation
moles divided by volume
how to go from cm3 to dm3
divide by 1000
atom economy equation ?
mass of desired product divided by sum of molecular masses x100
percentage yield equation :
actual divided by theoretical x 100
how many subshells do we have ?
4 : S, P D F
how many electrons does an orbital contain ?
2 e- per orbital
how many orbitals in s subshell
i orbital with 2 e-
how many orbitals in p subshell ?
3 orbitals with 6 e-
how many orbitals in d subshell
5 orbitals with 10 e-
how many orbitals in f subshell
7 orbitals with 14 e-
define ionisation energy ?
energy needed to remove 1 mole of outer electrons from 1 mole of atoms in their gaseous state to form 1 mole of 1 + ions also in gaseous state
what 3 factors affect IE ?
- atomic radius - as no e- increases - the distances between outer e- and nucleus increases , attraction decreases
- charge on nucleus - greater no protons = atomic radius decreases , force of attraction increases
shielding- e- in outer shell repel by e- in inner shells = reduced attraction
IE down group
atomic mass increases
no e- increases
more shielding takes place
repel
attraction decreases
NUCLEUR ATTRACTION is ioffset by these 2 factirs
IE across period
no protons increase
nuclear charge increases
force of attraction increases
atomic radius decreases
when does IE decrease
if goes from s orbital to p orbital
p orbital has higher energy level so less energy needed to remove e-
if e- are in pairs ~(in orbitals
) they will repel and shielding commences so IE is lower as attraction is lower .
