2 Atoms; Structure And Mass Flashcards
What is the plum pudding model?
JJ Thomson developed an atomic model where negatively charged particles were spread throughout the positively charged sphere of the atom. Like the raisins of a plum pudding, these negatively charged particles were called electrons.
Gold foil
Ernest Rutherford fired a beam of positively charged alpha particles and thin sheet of gold foil . Most alpha particles passed straight through the foil, producing flashes of fluorescent screen on the other side, but some particles were deflected as they passed through the foil, and some even bounced back. Rutherford concluded atoms must be predominantly empty space, but have a positive charge located in the centre.
What is electrostatic attraction?
Negative particles attract positive particles, so the electrostatic attraction of the atoms electrons to the protons within the nucleus, keep the atom bound together.
What is the atomic number of an element?
The number of protons in an atoms nucleus.
What is an elements mass number?
The number of the protons and neutrons in an atom.
What are isotopes?
Isotopes are atoms that have the same number of protons, but different number of neutrons. The more significant the number of neutrons are the more unstable. An element can become (radioactive)
What is relative atomic mass?
The relative atomic mass (Ar) is the average mass of atoms of an element relative to the mass of an atom of carbon-12
What is relative, isotopic mass?
The mass of an individual isotope of each element compared to the mass of an atom of carbon-12
What is relative isotopic abundance?
Can be expressed as a percentage abundance, it is the percentage of atoms with a specific atomic mass found in a naturally occurring sample of an element is known as its relative abundance.
How do you calculate the relative atomic mass of an element?
isotope mass x isotope abundance / 100
What is a mass spectrometer useful for?
Is a technique used to measure the mass of atoms or molecules. Determines the relative isotopic masses of elements and their isotopic abundance.
How does a mass spectrometer work?
1 the Sample is vaporised
2 it’s ionised using high energy electrons
3 ions are separated
4 accelerated, according to the mass to charge ratios (m/z) in an electromagnetic field
5 the ions with particular mass to charge ratio are detected by a device which counts the number of ions that strike it.
In a mass spectrum of an element:
- Peaks show number of isotopes
- Position of peak horizontally indicates relative isotopic mass
-The relative heights of the peaks correspond to relative isotopic abundance
