Atomic Structure Flashcards
Electron relative mass
1/1840
Nucleus
- carries virtually all of the mass of the atom
* positively charged
The chemical nature of an atom is determined by…
The number of electron it has, and their arrangement
Relative atomic mass
The average mass of one atom compared to 1/12 that of the mass of one atom of carbon-12
Relative isotopic mass
The mass of one atom of an isotope compared to 1/12 of the mass of one atom of carbon-12
Relative molecular mass
The average mass of a molecule compared to 1/12 of the mass of one atom of carbon-12
Relative formula mass
- the same as relative molecular mass, but for ionic compounds (as these are not molecules and giant covalent substances - the size of the molecule varies - it cannot have a precise molecular mass)
- used for compounds with giant structures
First ionisation energy
The energy required to remove one electron from each atom in one mole of gaseous atoms to produce one mole of gaseous ions with a 1+ charge
Equation for first ionisation energy
X(g) -> X+(g) -> e-
The first ionisation energy size provides information about…
… the force of attraction between the nucleus and the outer electrons
The attraction of an electron to the nucleus depends upon
- the nuclear charge
- the distance from the nucleus (greater = less attraction)
- shielding (more inner electrons = less attraction)
Nuclear charge
- the amount of protons relative to the amount of electrons
* the higher the charge, the greater the attraction
Trend of first ionisation energies across a period
- increase
- electrons are added to the same electron shell (same distance, shielding)
- nuclear charge increases; attraction to nucleus increases
- therefore more energy is needed to remove the electron
Trend across the periodic table for first ionisation energy
- group 1 has the lowest
* noble gases have the highest
Trend for first ionisation energy across a group
- decrease
* distance and shielding increase
Second ionisation energy
The energy required to remove one electron from each 1+ ion in one mole of gaseous ions to produce one mole of 2+ gaseous ions
Ionisation energy
The energy required to remove the readily available electron from an atom, by overcoming the attraction to the nucleus
General principles of first ionisation energy
- as nuclear charge increases, there is a stronger attraction, so ionisation energy increases
- as distance increases, attraction falls very rapidly - ionisation energy decreases
- shielding - inner shells repel outer electrons away from the nucleus
Spin-pairing
Causes repulsion; offsets attraction to the nucleus; paired e-s are removed more easily
Successive ionisions énergies
- give us important information about the electronic structure of an element
- determined which group an element is in
Trend for successive ionisation energies
- the second ionisation energy of an element is always greater than the first
- after each ionisation, nuclear charge increases
- the next electron must be removed from a greater attraction
E.g. successive ionisation energies for potassium
- first electron is removed from the outer-shell
- second electron has to be removed from an inner-shell; requires more energy
- the tenth electron has to be removed from the next inner shell