Chapter 2 (2.1.1/2) Flashcards
What is an isotope?
Isotopes are atoms of the same element with different numbers of neutrons and different masses
What does A and Z mean in isotope notation?
A = mass numbers Z = atomic number
What effect does changing the number of neutrons have on an element?
- No effect on chemical reactions
- increasing number of neutrons means larger mass, higher density, higher melting and boiling points and a slower rate of diffusion.
Define relative isotopic mass
The mass of an isotope relative to 1/12th of the mass of an atom of carbon-12
Define relative atomic mass
Ar, is the weighted mean mass of an atom of an element relative to 1/12th the mass of an atom of carbon-12
Describe the unit of atomic mass
u
- the mass of a carbon-12 isotope is defined as exactly 12u
- standard mass for atomic mass is 1u=1/12th a carbon-12 atom
- 1u is approximately the mass of a proton or neutron
What are the stages of mass spectrometry?
- sample placed in mass spectrometer
- sample vaporised, then ionised to form positive ions
- ions are accelerated - heavier ions move more slowly and are more difficult to deflect than lighter ions, so the ions of each isotope are separated.
- ions detected on a mass spectrum as a m/z. each ion reaching the detector adds to the signal, so the greater the abundance, the larger the signal.
Formula for mass-to-charge ratio (m/z)
m/z = relative mass of ion/relative charge on ion
What is a mass spectrometer used for?
- determining relative isotopic masses
- determining relative abundances of isotope
- calculation of relative atomic masses of an element from the relative abundances of its isotopes.
What are polyatomic ions?
Ions that contain more than one atom of more than one element bonded together.
What is a binary compound?
Contains 2 elements only. second element (the non-metal)’s name should end in -ide.
recall common ions: nitrate, carbonate, sulfate, hydroxide, ammonium, zinc, silver
- NO3^-, CO3^2-, SO4^2-, OH^-
- NH4^+, Zn^2+, Ag^+
