Topic 1 Atomic Structure and the Periodic Table Flashcards
(16 cards)
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.
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.
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.
Shielding
A decrease in the nuclear charge experienced by an outer shell electron caused by electron-electron repulsion between the outer shell electron and electrons from adjacent quantum shells.
