Definitions Flashcards
Atomic Number:
Number of protons in the nucleus of an atom.
Mass Number:
Sum of number of protons and neutrons in the nucleus of an atom.
Nuclear charge:
- Total charge of all the protons in the nucleus.
- It has the same value as the atomic number.
- Increases as you go across the periodic table.
Isotopes:
Atoms of the same element with the same number of protons but different number of neutrons in the nucleus, e.g. 35Cl and 37Cl.
Relative Atomic Mass:
Average mass of an atom of an element, relative to 1/12th of the mass of an atom of carbon-12.
Relative Isotopic Mass:
Average mass of an atom of an isotope relative to 1/12th
of the mass of an atom of carbon-12.
Relative Molecular Mass:
Average mass of a molecule relative to 1/12th of the mass of an atom of carbon-12.
Quantum shells:
Same as electron shells. They specify the energy level of an electron.
First Ionisation Energy:
The energy required to remove 1 mole of electrons from each atom in 1 moles of gaseous atoms to from 1 mole of gaseous 1+ ions
Second Ionisation Energy:
The energy required to remove 1 mole of electrons from each ion in 1 moles of gaseous 1+ ions to form 1 moles of gaseous 2+ ions (could be asked for any successive
ionisation energy)
Orbital:
A region in an atom that can hold up to two electrons with opposite spins.
Periodicity:
Trends in element properties with increasing atomic number.
Hund’s rule:
When electrons fill the orbitals, they occupy them singly before they pair up, e.g. in case of 2p^3 configuration, we would observe the following arrangement of electrons within the 2 p orbitals
Pauli Exclusion Principle:
Electrons within the same orbital must have opposite spins.
Aufbau Principle:
As the atomic number increases, the electrons are added to the orbitals in order of increasing orbital energy until all electrons are accommodated. Notable exceptions: Cr, Cu.
