Atomic Structure Flashcards
Which 2 subatomic particles are found in the nucleus?
protons and neutrons
Name the 2 subatomic particles with opposite charges.
protons and electrons
Which came first, the concept of atoms or the concept of electrons?
atoms
What is the relative charge on an electron?
-1
What is the relative charge on a proton?
+1
What is the relative charge on a neutron?
0
Atomic number - Z
the number of protons in an atom
Mass number - A
total number of protons and neutrons in an atom
Isotopes
atoms of an element that have the same number of protons but different numbers of electrons
Time of flight (TOF) mass spectrometer
determines the mass of individual atoms within a sample;
from the information the identity of an element or the relative molecular mass of a compound can be found, isotopic abundance can be determined.
TOF - types of ionisation
electrospray ionisation and electron impact ionisation
TOF - electrospray ionisation
tiny positively charged droplets are produced by gaining H+ ions.
TOF - electron impact ionisation
electrons are fired at a sample, knocking electrons off the target atoms to give 1+ ions.
TOF - acceleration
+ ions are attracted to a negatively charged plate and accelerate towards it; lighter ions and highly charged ions move faster than others.
TOF - ion drift
a beam formed of the + ions passes along the flight tube.
TOF - detection
+ ions arrive at the detector and pick up an electron, causing a current; lighter, faster ions arrive first.
How sub-shells are filled?
Fill from the bottom.
Each orbital can have only 2, opposite electrons.
Electrons repel, so fill orbitals singly before pairing.
Why is the 4s sub-shell filled before 3d?
The 4s sub-shell has lower energy than the 3d.
First ionisation energy
the energy required to remove a mole of electrons from a mole of atoms in the gaseous state to give a mole of gaseous ions, each with one positive charge.
Successive ionisation energies
First electron - easiest to remove.
Closer to the nucleus more energy is needed to remove electrons.
A big jump in ionisation energy can be seen between shells.
Trend in ionisation energies down a group
As the outer electrons get further from the nucleus, less energy is needed to remove them.
This means there is generally a decrease in ionisation energy down a group.
Trend in ionisation energy across a period
As nuclear charge increases, electrons become harder to remove.
This means ionisation energy generally increases across a period.
How do we calculate the number of neutrons in an atom?
mass number - atomic number
What type of ions are produced after ionisation in a time of flight mass spectrometer?
positive
