Atomic structure & periodic table Flashcards
What is the mass and charge of
- protons
- neutrons
- electrons
Proton : M= 1 C= +1
Electron: M= almost 0 C= -1
Neutron: M= 1 C= 0
What is meant by ‘atomic number’
The number of protons in the nucleus
What is meant by ‘mass number’
The total number of protons and neutrons in the nucleus
What is an isotope
An atom with the same atomic number but different mass number (same proton number different number of neutrons)
Define ‘ relative atomic mass’
The ‘mean mass’ of an atom of an element compared to 1/12th of the mass of an atom of carbon-12
Define ‘relative isotopic mass’
The mean mass of an atom of an isotope compared to 1/12th of the mass of an atom of carbon-12
When we talk about the ‘relative mass’ in general, what is meant?
Whenever we say relative mass of anything we are comparing the mass of an atom to the mass of a different atom.
How do you work out the ‘relative formula mass’ and when do we use this term ?
- Work it out by adding all the relative atomic mass values of the atoms together.
- We use it when referring to simple molecules
How do you work out the ‘relative molecular mass’ and when do we use this term ?
- Work it out by adding all the relative atomic mass values of the atoms or ions present.
- We use it when referring to giant covalent and ionic compounds
What does ‘Ar’ and ‘Mr’ stand for?
Ar refers to the relative atomic mass
Mr refers to the relative molecular mass
True or False:
The relative atomic mass of an ion is different to the relative atomic mass of the atom.
False - Electron number makes no difference to the mass number so the Ar of an ion is the same as the Ar of the atom.
What is meant by ‘ isotopic abundance’
the percentage of that isotope that exists in a naturally occurring sample
How to calculate the relative atomic mass of an element from its isotopic abundance?
Use the formula:
Relative atomic mass X isotopic abundance (do this for all the values and add them up) T
hen divide by sum of isotopic abundances
How to calculate the isotopic abundance using relative atomic masses:
Use the formula, rearrange to find X (missing value)
Relative atomic mass X isotopic abundance (do this for all the values and add them up)
Then divide by sum of isotopic abundances
What does the X axis of the mass spec tell us?
The X axis tells us the M/Z (mass to charge) ratio.
If the charge is +1, then this is the same as the relative isotopic mass.
What does the Y axis of the mass spec tell us?
The Y axis tells us the relative abundance (%) of the isotopes
What do mass specs do?
They measure the masses of atoms and molecules in samples
What is the ‘molecular ion peak’ aka ‘ The M peak’ and what does it tell us ?
It is the peak with the highest m/z charge and it tells us the molecular mass of a compound on a mass spec.
In what molecules do we have the M+1 peak and what causes it?
The M+1 peak tends to be found in molecules with a large mass and is caused by small samples of carbon-13 that may be present in the sample.
What are the steps to predicting the mass spec of diatomic molecules?
- Write out the different combinations of molecules that can be made using the different isotopes
- Multiply the abundances of the different isotope to the combinations made
- Add up the abundances for combinations that are the same
- Divide all the abundances by the smallest number to make whole number ratios
- Draw Mass spec according to the ratios produced
What is an orbital?
A region within an atom that can hold 2 electrons with opposite spins
What are 2 other words for electron shell?
Quantum shell
Energy level
What are quantum shells divided into?
Sub-shells
What are sub-shells made up of?
Orbitals
