Atomic Structure Flashcards
Definition of mass number
Number of protons and neutrons
Definition of atomic number
Number of protons
Isotope
Same number of protons and electrons different number of neutrons
Do isotopes of the same element have the same or different chemical properties
The same chemical properties as they have the same number of electrons
Do isotopes have the same physical properties
No the mass, density and boiling points will be different
What does the time of flight mass spectrometry do?
Measure The relative atomic mass of isotopes
Describe electron spray ionisation
The sample is dissolved in a volatile solvent
It is injected through a fine hypodermic needle to give a fine mist
The tip of the needle has a high voltage
So each particle is ionised by gaining a proton
Describe electron impact ionisation
High energy electrons from an electron gun are fired at the sample and knock off an electron
Explain how ions are accelerated in a time of flight mass spectrometry Omot
Positive ions accelerated by electric field
all with the same kinetic energy
Explain how ions are separated in a time of flight mass spectra
The positive ions with a lower MZ have the same kinetic energy as those with the higher MZ and ions with a lower MZ move faster therefore ions with a lower MZ detector first
Explain how ions are detected in a time of flight mass spectrometer
Positive ions hit the negatively charge plate (the detector) and pick up electrons
A current is generated when the ions gain an electron
The greater the abundance of the ions hitting the detector the bigger the current produced
Explain why it is necessary to ionised molecules and measuring their mass in a TOF mass spectrometry
Ions not molecules will interact with and be accelerated by an electric field
Only ions will create a current when hitting the detector
Relative atomic mass Ar
Average mass of one atom of element/
1/12th mass of an atom of 12C
define the plum pudding model
-ball of positively charged atoms
-with randomly scattered negative electrons
define the bohr model
-a small positively charged nucleus
-surrounded by a cloud of negative electrons
-with most of the atom as empty space
higher principal energy level/down a group
e.g Be : 1s2 2s2 Mg: 1s2 2s2 2p6 3s2
-ionisation energy decreases
-the electron is removed from a higher principal energy level
-the electron is further from the nucleus
-there is more shielding
-less energy is required to remove the electron as theres a weaker attraction between nucleus and outer e-
across a period
e.g Na: 1s2 2s2 2p6 3s1
Mg:1s2 2s2 2p6 3s2
-ionisation energy increases
-the number of protons increase
-shielding is constant/ atomic radius decreases
-More energy is required to remove the electron as theres a stronger attraction between outer e- and nucleus
1st ionisation energy of a group 3 element
e.g Mg: 1s2 2s2 2p6 3s2
Al: 1s2 2s2 2p6 3s2 3p1
-ionisation energy decreases
-the electron is removed from a higher energy p sub-level
-less energy is required to remove the electron/weaker attraction between nucleus and outer e-
ist ionisation energy of a group 6 element
e.g S 1s2 2s2 2p6 3s2 3p4
-ionisation energy decreases
-there is a pair of electrons in a p orbital
-extra repulsion means less energy is required to remove the electron
succesive ionisation energies
e.g C :1s2 2s2 2p2
C+ :1s2 2s2 2p1
-ionisation energy increases
- it is more difficult to remove an electron from a more positive ion
-radius decreases as positive charge increases
