Topic 1 - Atomic Structure and the Periodic Table Flashcards
Definition of Atomic Number
The atomic number of the element is the number of protons in the nucleus of an atom of that element.
Definition of Relative Atomic Mass
The relative atomic mass of an element is the weighted average mass of an atom of that element divided by 1/12 the mass of a carbon-12 atom.
Definition of Relative Molecular Mass
The relative molecular mass of an element (such as O2) or a compound (such as H2O) is the average mass of a molecule of that element or compund divided by 1/12 the mass of a carbon-12 atom.
Definition of Mass Number
The mass number of an isotope of an element is the sum of the number of protons and neutrons in the nucleus of an atom of that isotope.
Definition of Relative Isotopic Mass
The Relative Isotopic Mass is the mass of an atom of that isotope divided by 1/12 of the mass of a carbon-12 atom.
Definition of Isotopes
Isotopes are atoms of the same element that have the same number of protons but diffrent number of neutrons.
Four stages of Mass Spectrometry
Ionisation, Acceleration, Deflection, Detection
Ionisation stage in Mass Spectrometry
The electron gun emits a beam of high energy which removes the electron from the atom. This produces a cation.
Acceleration stage in Mass Spectrometry
The plates of positive potential accelerate the cation.
Deflection stage in Mass Spectrometry
The magnetic field produced by the electromagnet exerts a centripetal force on the cation which causes it to deflect.
The greater the mass, the more momentum, defelction decreases.
Definition of First Ionisation Energy
The first inionisation energy of an element is the energy required to remove one electron from a mole of gaseous atoms of that element.
Equation: A (g) –> A+ (g) + e-
General trend of first ionisation energy down a group
As you go down the group the atomic shielding increases as well as the number of protons. However the most significant factor is the increase in atomic radius. This makes the elctron furthests from the nucleus easier to lose.
General trend of first ionisation energy across a group
Across the period the atomic shielding remains roughly the same and its change is mostly insignificant. The number of protons increases meaning that the atomic radius decreases. This means the forces of attractions between the nucleus and its outermost electron are stonger. Therefore more energy is required to overcome that bond.
Anomilies to the first ionization trends
Oxygen - It contains an orbital with 2 electrons meaning there is repulsion. It is easier to remove an electron
Boron - Contains a p orbital. Thereofre easier to lose an electron.
Definition of an Orbital
An orbital is a region in space occupied by one or two electrons.
