Unit 1.3 Flashcards
First ionisation energy def?
the energy required to remove 1 electron from each atom in 1 mole of gaseous atoms
Ionisation of Sodium?
Na(s) —– Na+ + e-
What does removing successive electrons do?
increases the ionisation energy as positive ions are formed
What is the attraction of the positive nucleus dependent on?
shielding
atomic radii
size of the positive charge
Shielding?
all electrons repel each other as they’re negatively charged
electrons in their inner shell repel electrons in their outer shell
This reduces the effect of the positive nuclear charge + more inner shell, the smaller the attractive force and the lower the ionisation energy
Atomic radius def?
the force of attraction between the nucleus and the outer electron decreases as the distance between the, increases and the lower the ionisation energy
What does the size of the positive nuclear charge mean?
the larger the ionisation energy
Shielding effect def?
the repulsion between electrons in different shells
Successive ionisation energies?
a measure of the energy needed to remove each electron in turn until all of the electrons have been removed from the atom
for example?
Sodium
11 electrons so 11 successive ionisation energies
for example the third ionisation energy = a measure of how easily the 2+ ion loses its electron to form a 3+ ion
Na2+(g) —— Na3+(g)+e-
Why do successive ionization energies always increase?
there is always a greater effective nuclear charge as the same number of protons are holding fewer and fewer electrons
As an electron is removed, there is less electron repulsion and each shell is drawn closer to the nucleus
As the atomic radius decreases the nuclear attraction increases
Atomic radius?
the distance between the positive nucleus and the valence electron
Emission and the absorption spectrum
Light takes the form of an electromagnetic wave
visible light is part of the electromagnetic wave
Different types of wavelengths?
radio waves
microwaves
infrared
invisible
ultraviolet
x rays
gamma rays
Radiowave?
has the longest wavelength but lowest frequency
Gamma rays?
highest frequency but shortest wavelength
What is the equation?
C = F LAMDER
C = speed of light (3x10^8m/s)
F = frequency (Hertz)
Lamder = wavelength(m)
Equation for energy?
E = hf
E= energy(J)
h= 6.63 c 10 ^-34 )(Js)
f = hertz
What is energy directly proportional to?
Frequency
what is Energy inversely proportional to?
wavelength
What is the pattern along the waves?
Their wavelengths decrease going from Radiowaves to Gamma rays
Visible length?
Red = 650 - 700 nm
Yellow = 580n
Green = 540 nm
Blue = 480nm
Violet = 400 nm
What is absorption spectra?
light of all visible wavelengths called whitelight
all atoms and molecules absorb light of specific wavelength
when white light is passed through the vapor of an element , certain wavelengths will be absorbed by the atoms + removed from the light
where the wavelength has been absorbed, black lines will appear on a coloured background known as an absorption spectrum
What is an emission spectra?
when atoms are given energy ( by heating ot being placed in an electric field), the electrons are excited from a lower to higher energy level
when the source is removed, the electrons leave their excited state and fall from a higher to lower energy level, releasing a photon of light
the photon of a light has a specific wavelength and frequency
Emission spectrum = coloured lines on black background
How would the spectrum appear continous?
if electron energy levels were not quantised
When is it discrete?
single lines
When is it continous?
rainbow
What is the Hydrogen Spectrum?
an atom of Hydrogen only has 1 electron, so gives the simplest emission spectrum
this is seen as a series of seperate lines in the UV, visible and Infrared region
What is in the visible region of the spectrum?
only the Balmer series
What is in the infrared region?
Lyman
Paschun
Energy levels?
n= 1Lyman (UV)
n= 2Balmer(Visible)
n=3Paschun
(Infrared)
n=4Brackett
n=5Pfund
n=6Humphreys
Ionisation energy of Hydrogen?
The spectral lines become closer together as the Frequency of the radiation increases until they converge to a limit
What is the convergence limit>
when the spectral lines become so close together, they form a continuos bond which is radiation and spectral lines cannot be distinguished
the convergence limit corresponds to the point at which the energy of an electron is no longer quantitised, so the nucleus has lost all influence over the electron + the atom is ionised
Relative atomic mass?
the average mass of 1 atom of an element relative to 1/12th the mass of 1 atom of Carbon 12
Relative isotopic mass?
the mass of an atom of an isotope relative to 1/12th the mass of carbon 12
Relative Formula mass?
the sum of the Relative atomic mass of all the atoms present in its formula
What is the Mass Spectrometer used for?
used to find the Relative atomic mass of an element
measures 2 factors
the mass of each different isotope of an element
measures the relative abundance of each isotope
Process of MASS SPEC
V
I
A
D
1)the sample must be vaporised
2)the sample is placed in an ionisation chamber
3)the sample is bombarded with a stream of electrons
If the collision is sufficiently energetic, one or more electrons is removed to create a positive ion (mainly 1)
4) An electric field accelerates the positive ions to high speed
5) Deflection - different ions are deflected by a magnetic field
What is it dependent on?
the mass of the ion (light deflected more than the heavy ones)
What alters its deflection?
the charge of the ion
the higher the charge, the ,pre the deflection
Deflection def?
A beam of ions is detected electrically, only ions with the correct M/Z will reach the detector
the other ions collide with the wall, pick up the electrons + are neutralised and removed by the vaccum pump
M/Z?
mass to charge ratio
What is the purpose of the vaccum Pump?
to remove ions + our molecules to prevent collisions
What can be varied to remove ions with the incorrect m/z ratio?
the strength of the magnetic field
Fragmentation?
the splitting of molecules in a mass spec in smaller parts
Uses of the mass spectrometry?
Identifying unknown compounds
( drug testing)
Identifying compounds in forensic science
analysing molecules in space
molecular ions?
positive ions in a mass spectrometer from the whole molecule
Volume of gas?
at a standard temp of O degrees and 1 atm, 1 mole of gas is known as molar gas volume
At a standard temp of 25 degrees, 1 atm, 1 mole of gas occupies 24.5 dm3
What is Boyles law?
1662
at a constant temp, the volume of a fixed mass of gas is inversely proportional to its pressure
Absolute 0?
-273 degrees
where molecules do not vibrate + are still and constant
Avagrado’s principle?
equal volumes of different gases at the same temp + pressure contain the same number of molecules
V is directly proportional to N
constant temp + pressure
What is the formula?
pv = nRT
What is the number of moles but only in 1 dm3 =?
in 1 dm3, the concentration
