Atomic Structure Flashcards
What is the history of the atom?
- Robert Boyle - 1661 (chemical elements)
- John Dalton - 1803 (elements consist of atoms/invisible particles)
- J J Thomson - 1897 (plum pudding model)
- Neils Bohr - 1913 (atom is orbited by electrons)
- Ernest Rutherford - 1911 (most of mass of an atom is in nucleus)
- Erwin Schrodinger - 1926 (wave equation for electron movement)
What is the mass of a proton, electron and neutron?
Proton- 1
Electron- 1/1840
Neutron- 1
What is the charge of a proton, electron and neutron?
Proton- +1
Electron- -1
Neutron- 0
What is the arrangement of sub-atomic particles?
Protons and neutrons are in the centre of the atom, held by a strong nuclear force
What is the definition of relative atomic mass?
The average mass of an atom of an element compared to 1/12th the mass of carbon 12.
What is an isotope?
An element with the same number of protons but different number of neutrons.
Why do isotopes have all the same chemical properties?
They chemically react in the same way because they have the same electron configuration.
What is the equation for the number of electrons in each shell?
2n^2 n=number of the shell
What is the relative abundance of an isotope?
Percentage of atoms with a specific atomic mass found in a naturally occurring sample of an element.
What is the purpose of mass spectrometry?
To find the relative abundance of each isotope of an element.
What does a mass spectrometer show?
A series of peaks on a graph with relative abundance of isotopes against mass/charge, this can be used to calculate relative atomic mass.
Mass spectrometry can identify elements
What are the conditions required for mass spectrometry to take place?
- In a vacuum, to prevent ions from colliding with air molecules
- Elements in a gaseous state - solids are vaporised
What are the 4 stages of mass spectrometry?
- Ionisation
- Acceleration
- Ion drift
- Detection
What occurs in ionisation / what are the two different types?
Electrospray - sample is dissolved in volatile solvent and this causes the addition of a proton
Electron impact - electrons are fired from electron gun at vaporised sample this causes an electron to be knocked off (1+ ion)
Ionisation is where atoms are converted to ions
What occurs in acceleration?
Ions are accelerated using an electric field so they have the same kinetic energy
Lighter particles have a higher velocity
What occurs in ion drift?
Ions pass through hole in negatively charged plate through flight tube
What occurs in detection?
Lighter ions arrive first due to having higher velocities
The more electrons that his the plate the larger the current and the bigger the peak
What occurs in data analysis?
Data is recorded in a mass spectrum
Why is a negatively charged plate used in mass spectrometry?
To attract positive ions
What are the 4 sub-levels? + how many electrons/orbitals do they have/hold?
s- 2 (1 orbital)
p- 6 (3 orbitals)
d- 10 (5 orbitals)
f- 14 (7 orbitals)
What is the aufbau principle?
Lowest energy sub-levels are occupied
Whats hunds rule of maximum multiplicity?
If two or more orbitals of equal energy are available the electrons will occupy them singly before becoming paired
What is the Pauli Exclusion principle?
Two electrons in the same orbital must have opposite spins (up/down arrows)
Which elements do not follow the rules of normal electronic configurations?
Chromium, Copper
What is coppers electron configuration?
1s2 2S2 2P6 3S2 3P6 4S1 3d10
What is chromium electron configuration?
1𝑠2 2𝑠2 2𝑝6 3𝑠2 3𝑝6 4𝑠1 3𝑑5
Why do copper and chromium contain one electron in their 4s orbital?
4s and 3d orbitals lie close together in energy, if 3d is half full or completely full is a lower energy arrangement
What is ionisation?
Process in which atoms lose of gain electrons and become ions
What is the first ionisation energy?
The energy required to remove one electron from one mole of atoms in a gaseous state
It is a measure of strength of attraction between outermost electron and nucleus
M(g) -> M+ (g) + e-
What factors affect ionisation energy?
- charge on the nucleus
- distance of electron from the nucleus
- number of electrons between outer electrons and nucleus
- whether electron is paired or alone in its orbital
What is the general trend of first ionisation energies of period 3 elements? + why does it have this trend?
Increase in ionisation energy as you move along the period
- number of protons increases
- similar shielding
- atomic radius decreases
What are the anomalies in the graph?
First ionisation energy of sulphur is lower than phosphorus even though it is further along the period
This is because they both have their highest energy electron in the 3p orbital but in Sulphur the electron is paired but in Phosphorus each 3p orbital is occupied. Therefore by mutual repulsion between paired electrons means that less energy is required to remove one in Sulphur.
What is another anomaly of the graph?
First ionisation of Al is less than Mg this is because the electron removed to ionise Al is in a 3p sub-shell which is of higher energy than the electron removed in the 3s sub-shell to ionise magnesium thus removing an electron from a higher energy orbital requires less energy.
What is the second ionisation energy and equation?
The energy required to remove one electron from each ion in 1 mole of gaseous 1+ ions to from 1 mole of gaseous 2+ ions
M+(g) -> M2+(g) + e-
Which ionisation energy requires less energy?
First ionisation energy
What is the ionisation energy trends in group 2?
decrease in ionisation energy
Going down the group, nuclear charge increases
The positive charge felt by the electron from the nucleus is less than the full nuclear charge because inner electrons shield the nuclear charge
