module 2: foundations in chemistry Flashcards
what are isotopes?
atoms that have the same number of protons and electrons, but different number of neutrons
what is the atomic number?
the number of protons in an atom
what is the mass number?
the sum of protons and neutrons in an atom
what are the relative charges on the subatomic particles?
proton = 1+
neutron = 0
electron = 1-
where are electrons found in an atom?
arranged around the nucleus in shells
what is the overall charge of an atom?
zero
why do different isotopes of an element react in the same way?
- chemical reactions involve the electrons surrounding the nucleus
- different isotopes have the same number of electrons
- the number of neutrons has no effect on reactions of an element
what is an ion?
a charged atom
what are cations?
positive ions
what are anions?
negative ions
what is the relative isotopic mass?
the mass of an isotope relative to 1/12th of the mass of an atom of carbon-12
what is the relative atomic mass?
the weighted mean mass of an atom of an element relative to 1/12th of the mass of an atom of carbon-12
what properties does the weighted mean mass take into account?
- the percentage abundance of each isotope
- the relative isotopic mass of each isotope
how are the percentage abundances of the isotopes in a sample of an element found using a mass spectrometer?
- a sample is placed in the mass spectrometer
- the sample is vaporised and then ionised to form positive ions
- the 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
- the ions are detected on a mass spectrum as a mass-to-charge ratio m/z
what is a binary compound?
a compound that contains two elements only
