Atomic Structure Flashcards
What is the structure of an atom?
- Mostly empty space
- Dense nucleus containing protons and neutrons giving it an overall positive charge
- Electrons orbit nucleus in orbitals
What are the 3 subatomic particles, their charges and relative masses?
Protons: Positive charge +1, relative mass of 1
Electrons: Negative charge -1, relative mass of 1/1836
Neutrons: Neutral charge 0, relative mass of 1
What holds the atom together?
The electroststic attraction between the positive protons and negative electrons
How is an ion formed?
When an atom gains or loses electrons causing them to become charged
What does the atomic number tell you amd what does it determine?
Atomic number tells you the protons on an atom, it determines the atom or ion
What calculation can be used to determine the number of protons on an atom
Number of protons = Mass number - number of neutrons
Why does am atom have a neutral charge overall?
An atom will have the same number of protons and electrons and so this cancels out causing a neutral charge
What calculation can be used to find out the number of neutrons?
Number of neutrons = Mass number - number of protons
What is an isotope?
An element that contains the same number of protons and electrons but a different number of neutrons
Why do isotopes display the same chemical characteristics?
They have the same number of electrons in their outer shell, which take part in chemical reactions
Why do isotopes have different physical properties?
They are overall neutral particles and so only add mass to the atom, meaning the physical properties are different in terms of small changes in mass and density
What is the calculation of relative atomic mass of isotopes?
(Relative abundance iso1 × mass iso1) + (Ar iso2 × mass iso2) etc / (sum of abundances
What is the formulary for relative atomic mass?
Mass = moles × Mr/Ar
What is tine of flight mass spectrometry used for?
Determining the relative atomic mass of an element based on the abundance and mass of each isotope
What is electrons impact ionisation?
Used for lower Mr compounds/elements
- Sample injected under low pressure and vaporised
- Electrons from ‘electron gun’ fired at it knocking off an electron from each atom
- Each atom becomes a +1 ion
What is electrospray ionisation?
Used for high Mr compounds
- Sample dissolved in volatile solvent and injected through hypodermic needle to give fine mist
- Particles becime +1 ions by gaining a proton from the solvent
What is the acceleration step of ToF mass spectroscopy?
- Ions are accelerated towards the negative plate and so all have the same kinetic energy
- This means that the speed depends on the mass of the ion
- Each ion will have a different time of flight
What is the equation for kinetic energy, and then the rearranged equation for velocity?
KE = ½mv²
v = (square root of) 2KE/m
What is the Ion Drift step of ToF mass spectroscopy?
- Particles are now in Ion Drift area, where they enter the flight tube
- These particles accelerated towards the negative plate, lighter ions give faster/are more deflected
- Deflection also depends on number of positive charges - the more the ion is charged the more it’s deflected
What is the Detection stage of ToF mass spectroscopy?
- Ions reach the end of the tube and strike negatively charged plate
- +1 ions neutralised by gaining an electron
- This process generates a flow of electrical charge and so signals can be received
What is the number of electrons each quantum shell can hold - up to 4 shells?
n = 1: up to 2 electrons
n = 2: up to 8 electrons
n = 3: up to 18 electrons
n = 4: up to 32 electrons
What are the four subshells and how many electrons can they each hold, what order dp they increase?
s orbital = 2
p orbital = 6
d orbital = 10
f orbital = 14 (not really used in a level)
s<p<d<f
