Atomic structure Flashcards
What is the atomic number?
The number of protons in the nucleus.
What is the mass number?
The number of protons and neutrons in the nucleus.
What is an isotope?
Different number of neutrons but the same number of protons.
What is the mass spectrometer used for?
Analysing samples of elements in terms of the isotopes they contain and their relative amounts.
Why must the system of a mass spectrometer be kept in a vacuum?
So the ions cannot collide with molecules in the air.
How do you calculate relative atomic mass?
mean mass of an atom of the element / mass of one atom of 12C x12
How do you calculate relative molecular mass?
mean mass of a molecule / mass of one atom of 12C x12
How do you calculate relative isotopic mass?
Mass of one atom of the isotope / mass of one atom of 12C x12
When is m/z the same as the mass of the ion?
When the ion’s charge is +1
Why is there a decrease in ionisation energy between magnesium and aluminium in period 3?
The outer electron in the p sub-level is of slightly higher energy than the s sub-level, so is easier to remove.
Why is there a decrease in ionisation energy between phosphorus and sulfur?
In sulfur two of the p-electrons are paired and so repel making it easier to remove.
What is electrospray ionisation?
Sample is dissolved in a volatile solution and forced through a fine needle connected to a high voltage which removes one electron. This produces tiny positively charged droplets.
What is electron impact ionisation?
Sample is vaporised and high energy electron are fired at it from an electron gun. Knocks off one electron from each particle.
