Atomic Structure and Periodic Table

Comprehensive vocabulary flashcards covering sub-atomic particles, mass spectrometry, ionisation energy definitions and trends, electronic configurations, and periodicity based on lecture notes.

Atomic number ($Z$)

The number of protons in the nucleus of an atom.

Mass number ($A$)

The total number of protons and neutrons in the atom.

Isotopes

Atoms with the same number of protons, but different numbers of neutrons.

Relative isotopic mass

The mass of one atom of an isotope compared to one twelfth of the mass of one atom of carbon-12.

Relative atomic mass ($A_r$)

The average mass of one atom compared to one twelfth of the mass of one atom of carbon-12.

Relative molecular mass ($M_r$)

The average mass of a molecule compared to one twelfth of the mass of one atom of carbon-12.

Mass spectrometer

An analytical instrument used to determine all the isotopes present in a sample of an element and to identify elements by measuring their $m/z$ (mass/charge ratio) and abundance.

$$m/z$$

The mass-to-charge ratio measured for each isotope or ion in a mass spectrometer.

Molecular ion (parent ion)

The peak in a mass spectrum with the largest $m/z$, which is caused by the complete, unfragmented molecule and equals the $M_r$ of the molecule.

First ionisation energy

The energy required when one mole of gaseous atoms forms one mole of gaseous ions with a single positive charge ($H_{(g)} \rightarrow H^+_{(g)} + e^-$).

Second ionisation energy

The energy required when one mole of gaseous ions with a single positive charge forms one mole of gaseous ions with a double positive charge ($Ti^+_{(g)} \rightarrow Ti^{2+}_{(g)} + e^-$).

Shielding

The repulsion of an electron in an outer shell by electrons in complete inner shells, which weakens the electrostatic attraction of the nucleus.

Successive ionisation energies

The series of ionisation energies required to remove electrons sequentially from an atom; each successive value is larger because removing an electron forms a positive ion that increases attraction on the remaining electrons.

Periodicity

The repeating pattern of physical or chemical properties observed when going across the periods of the periodic table.

Orbital

A mathematical probability region of finding an electron at any point within certain spatial distributions around the nucleus, holding up to $2$ electrons of opposite spin.

Sub-energy level capacities

The defined electron capacities for sub-levels: an $s$ sub-level holds up to $2$ electrons, $p$ holds up to $6$, $d$ holds up to $10$, and $f$ holds up to $14$.

Hund's rule

The rule stating that when filling up sub-levels containing multiple orbitals, each orbital is filled singly before electrons begin to pair up.

$s$ block element

An element whose outer electron is filling an $s$-sub shell.

Macromolecular structure

A giant lattice structure (such as silicon) held together by many strong covalent bonds between atoms, requiring high energy to break and resulting in very high melting and boiling points.

Simple molecular structure

A structure composed of discrete molecules (such as $Cl_{2(g)}$, $S_{8(s)}$, or $P_{4(s)}$) held together by weak London forces, requiring little energy to separate them.