2.1.1 Atomic structure and isotopes Flashcards
Define isotope
atoms of the same element with a different numbers of neutrons and different masses
-Same chemical properties (electrons are not altered) but varied physical properties (relative atomic mass changes)
Define molecule
a group of two or more atoms held together by covalent bonds
Define relative atomic mass
weighted mean mass of an atom of an element compared to 1/12th of the mass of one atom of carbon 12
Define relative isotopic mass
**Mass **of an isotope compared with 1/12th of the mass of carbon-12
Define relative molecular mass
weighted mean mass of a molecule compared to 1/12th of the mass of one atom of carbon-12
How can you calculate relative molecular/formula mass ?
add up the relative atomic mass values
Molecular (simple molecules such as ethene)
Formula (Giant structures such as silicon dioxide)
What is the formula for relative atomic mass ?
∑ isotope mass x isotope abundance / 100
OR (Isotope mass x relative abundance) / total relative abundance
What is the purpose of mass spectrometry ?
the determination of relative isotopic
masses and relative abundances of the
isotope
Abundance is on the Y-axis and isotopic mass (shown as m/c) is on the x-axis
How do you calculate relative atomic mass of an element based on a mass spectra?
- Carefully read values off the graph
- Calculate ∑ isotope mass x isotope abundance / 100.
What is percentage abundancy ?
% value of the number of isotopes available in nature for a given element
How do you calculate percentage abundancy ?
* (x) = a % of the first value (107)
* **(1-x) **= a % of the second value (109)
* Relative atomic mass formula is used
* 107 (x) + 109 (1-x) = 107.9 (given relative atomic mass)
* Solve for X, then multiply by 100
* if x is 55% than (1-x) x 100 will be 45%
