ATOMS, IONS AND COMPOUNDS
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Which 2 subatomic particles are found in a nucleus?
Protons Neutrons
Protons and neutrons have the same…
Mass
What is the relative mass of an electron?
1/1836 th the mass of a proton
What charge does a proton have?
Positive charge 1+
What charge does an electron have?
Negative charge 1-
What charge does a neutron have?
No charge, it is neutral
Where is most of the mass of an atom found?
In the nucleus
Atoms contain the same number of….
Protons and electrons
What is the overall charge of an atom?
Zero The charges cancel out - an atom is neutral
What is an Isotope?
Isotopes are atoms of the same element with different numbers of neutrons and different masses They still have the same number of electrons
Does the number of neutrons have an effect in the reactions of an element?
No, therefore different isotopes of an element react in the same way
What is the name of “Heavy water”
Deuterium
What is special about Deuterium compared to normal water?
Greater density Higher melting point and boiling point (by a little) Water would freeze at a higher temp (if deuterium)
What is an ion?
A charged atom Different numbers of electrons So there is an overall charge
What are cations?
Positive ions More protons than electrons Overall positive charge
What are anions?
Negative ions More electrons than protons Overall negative charge
What is the difference between ions and atoms?
Same number of protons But different number of electrons
What is Relative Isotopic Mass?
Relative Isotopic mass is the mass of an isotope relative to 1/12th of the mass of an atom of carbon 12
Mass number is…
MASSive (the bigger number) Sum of the protons and neutrons
What is Relative Atomic Mass?
Relative atomic mass, Ar, is the weighted mean mass of an atom of an element relative to 1/12th of the mass of an atom of carbon 12
How are the percentage abundances of isotopes found?
Using a mass spectrometer
Describe how a mass spectrometer is used to find the percentage abundances of isotopes
• 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 ones, so the ions of each isotope are separated • The ions are 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
How do you determine the m/z ratio of an element?
Relative mass of ion / Relative charge of ion
What does the M in m/z stand for?
Mass