Atomic Structure and Periodicity

Comprehensive vocabulary flashcards covering atomic structure, sub-atomic particles, mass spectrometry, and ionisation energy principles based on the lecture notes.

Plum pudding model

A model of the atom where electrons are located in circular arrays within a sphere of positive charge.

Sub-atomic particles

The smaller particles that make up atoms: protons, neutrons, and electrons.

Nucleons

A collective term for protons and neutrons because they are found in the nucleus.

Relative mass of an electron

$$\frac{1}{1840}$$

Strong nuclear force

The force that holds protons and neutrons together in the nucleus, acting only over very short distances to overcome the repulsion between protons.

Atomic number $Z$

The number of protons in the nucleus of an atom, defining its chemical identity.

Mass number $A$

The total number of protons plus neutrons in the nucleus of an atom.

Isotopes

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

Half-life

The time taken for half of the radioactivity of a radioactive isotope to decay; for ${}^{14}C$, this is $5730$ years.

Quantum mechanics

A theory developed in the 1920s that describes the atom mathematically, treating electrons as having properties of waves as well as particles.

Relative atomic mass ($A_r$)

$$\frac{\text{average mass of 1 atom}}{\frac{1}{12} \text{ mass of 1 atom of } {}^{12}C}$$

Electrospray ionisation

A technique in mass spectrometry where the sample is dissolved in a volatile solvent and forced through a fine hollow needle connected to a high voltage supply to produce positively charged droplets.

Electron impact

A technique in mass spectrometry where high energy electrons from an electron gun are fired at a vaporised sample to knock off an electron, forming a $1+$ ion.

Mass spectrum

A plot generated by a mass spectrometer where the peak height represents relative abundance and the horizontal scale represents the mass/charge ratio ($m/z$).

Atomic orbital

A volume of space in which there is a $95\%$ probability of finding an electron, with shapes represented by the letters $s$, $p$, $d$, and $f$.

Spin

A property of electrons where two electrons in the same orbital must have opposite directions, usually represented by arrows pointing up or down.

Ionisation energy (IE)

The energy required to remove a mole of electrons from a mole of atoms in the gaseous state, measured in $kJ\,mol^{-1}$.

Successive ionisation energies

The energies required to remove electrons one by one from an atom, starting from the outer electrons and working inwards.

Shielding

The effect where inner electrons reduce the actual positive charge 'felt' by an electron in the outer shell from the nucleus.