1 - Atomic Structure Flashcards
What is a mass spectrometer used for?
Determining masses of separate atoms to determine relative atomic masses, and to identify elements.
Why are mass spectrometers kept under a high vacuum?
So that air particles do not collide with the ions
What are the four key stages of mass spectrometry?
Ionisation
Acceleration
Ion drift
Detection
What state are samples in mass spectrometry in?
Gaseous
Explain the ionisation stage of mass spectrometry.(electron bombardment)
An electron gun knocks out electrons from sample atoms to form positive ions.
Most form 1+, some form 2+
Explain ion drift.
Ions pass through a hole in the negatively charged plate, forming a beam, and travel along the flight tube to a detector.
Explain the acceleration stage of mass spectrometry.
The positive ions are attracted towards negatively charged plates. Lighter ions go faster. Some ions pass through slits in the plates which forms the ions into a beam.
What is the relative mass of an electron?
1/1840
Explain the detection stage of mass spectrometry.
Lighter ions arrive first as they are faster. Flight times are recorded. Positive ions accept an electron which causes current to flow.
Explain data analysis in mass spectrometry.
Signal from detector is passed to a computer which generates a mass spectrum.
What are the three rules for allocating electrons to atomic orbitals?
Lower energy atomic orbitals are filled first
Atomic orbitals fill singly before pairing because electrons repel
No atomic orbital holds more than two electrons
Describe the trend in ionisation energies across a period.
They increase as the nuclear charge increases
Explain the trend in ionisation energies down the groups
Decreases down the group as the outer electron is further from the nucleus. There is also electron shielding.
What is the atomic number of an element?
Number of protons
What is the mass number of an element?
Number of protons + number of neutrons
