Atoms, Ions and Compounds
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What is the mass of an electron?
1/1836th of the mass of a proton
What is the mass of a proton/neutron?
1
Define atomic number
The number of protons in the nucleus of an atom
Define isotope
Atoms of the same element with same number of protons, different number of neutrons and different masses.
What does ‘A’ represent?
A is the mass number (number of protons + number of neutrons)
What does ‘Z’ represent?
Z is the atomic number ( number of protons)
Do isotopes of the same element react differently? Why?
No. Isotopes of same element have same number of electrons, only a different number of neutrons and therefore there is no effect on reactions of element.
Do isotopes have different physical properties?
Yes. Higher mass isotopes may have higher boiling points, melting points and densities.
What is an ion?
A charged atom where the number of electrons is different to the number of protons.
What is a cation?
A positive ion. Number of electrons fewer than number of protons. Overall positive charge.
What is an anion?
A negative ion. Number of electrons greater than number of protons. Overall negative charge.
Why can you not add together all relative masses of proton, neutron and electron to get total mass?
Strong nuclear force holding together the protons and neutrons comes at the expense of a loss of a small proportion of mass
What is the standard isotope used?
Carbon-12
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
The weighted mean mass if an atom of an element relative to 1/12th of the mass of an atom of carbon-12
What two factors does the weighted mean mass take into account?
Percentage abundance of each isotope Relative isotopic mass of each isotope
What equipment is used to calculate percentage abundance of isotopes?
Mass Spectrometer
Describe process of using mass spectrometer
Sample placed in mass spectrometer Sample is vaporised Sample is ionised to form positive ions Ions are accelerated Heavier ions move more slowly, isotopes are separated Ions are detected on mass spectrum
What does m/z signify?
mass to charge ratio. Relative mass of the ion/ relative charge on ion