Atoms, Ions And Compounds Flashcards
What are the three fundamental subatomic particles?
Protons, neutrons and electrons
What do both protons and neutrons create?
The nucleus and are collectively called nucleons
What does the mass number represent?
The total number of nucleons (protons and neutrons) in the nucleus
What does the atomic number represent?
The number of protons in the nucleus, which uniquely identifies the element
What is a neutralatom?
An atom which contains an equal number of protons and elections.
What makes the atom a negative ion (anions)?
When there’s more electrons than protons
E.g. A particle with 1 proton and 2 electrons would be a negative ion with an overall charge of -1
What would a particle with 3 protons and 2 electrons considered?
A positive ion. (Cations)
Who proposed the solid sphere model during the early 19th century? And what does it suggest?
John dalton, this model suggests that atoms were indivisible, solid spheres
It also suggests that different elements were made up of different types of these spheres.
What was Thomasons model called and what did it depict?
plum pudding model (1897)
The discovery of the electron by J.J. Thomson proved that atoms were divisible.
His ‘plum pudding’ model depicted atoms as a positively charged ‘pudding’ with negative electrons embedded throughout, similar to the raisins in a plum pudding.
What was Rutherford’s experiment about and what did it prove?
Gold foil experiment,
Firing alpha particles (positively charged) at a sheet of thin gold foil inside a vacuum
Plum pudding = the positive”pudding” slightly deflect most particles
Contrary to expectations - most alpha passed straight through, only few deflected at large angles or even bouncing back
Who discovered the proton?
Henry Moseley who showed that the nuclear charge increases by one unit from one element to the next.
Led to Rutherford to identify positively charged particles within the nucleus, which he named protons
Who predicted then who discovered the neutron?
Rutherford speculated about the existence of another type of nuclear particle.
James Chadwick later discovered the neutron, which provided the mass needed to account for the discrepancy in the nucleus’s weight.
Who introduced the election shells?
Niels Bohr who suggested a model in which:
Electrons orbit the nucleus in specific energy levels, or shells.
They can jump between these shells by absorbing or emitting light of particular wavelengths.
What is the definition of an element?
Substances made up of only one type or atom, where all the atoms of a substance have the same number of protons
What is the definition of an isotope?
Atoms of the same element that have the same number of protons but different numbers of neutrons
Most elements are made up or a mixture of isotopes.
Chemical vs physical properties of isotopes
Chemical properties:
- isotopes have the same electron configuration
- this means they have the same chemical properties (e.g. Reactivity)
Physical properties:
- isotopes have slightly different isotopes (eg. Mass and density)
- this is because physical properties depend on atomic mass.
What is the relative isotopic mass?
The mass of an atom of an isotope compared to 1/12 the mass of a carbon-12 atom.
E.g. The relative isotopic mass Of the 2 main chlorine isotopes ( 35 CL and 37 CL ) are 35.0 and 37.0 respectively
What is the relative atomic mass?
The weighted mean mass of an atom of an element compared to 1/12 the mass of a carbon -12 atom.
What is the relative molecular mass?
The average mass of a molecule compared to 1/12 the mass of a carbon- 12 atom.
E.g. For ethanol (C2H5OH) = (2x12) + (6x1) + (1x16) =46.
What is the relative formula mass?
Used for ionic compounds. Calculated by adding up the ar values of all the ions in one formula unit.
E.g. For calcium fluoride (CaF2).= (1x40.1) +(2x19.0) =78.1
What is the formula to find the ar from isotopic abundance?
sum of (isotopic mass X isotopic abundance)
Ar= ——————————————————————
Sum of abundance of all Isotopes
What is mass spectrometry?
Mass spectrometry is used to identify different isotopes and Find the overall relative atomic mass of an element.
What is “time of fight” (tof)?
Time of flight mass spectrometry records the time it takes for ions of each isotope to reach a detector.
Using this, “spectra” can be produced snowing each isotope present. The signals reflect the abundances of the isotopes present.
From a spectra, how can the Ar be calculated?
Sum of (m/z x abundance)
Ar = —————————————-
Total abundance
