(🟠 TOPIC 1) Key Definitions … Flashcards
Atomic number (z)
The number of protons in the nucleus of an atom of a certain element
Mass number (A)
The sum of the number of protons and the number of neutrons in the nucleus of an atom of a certain element
Isotopes
An atom of the same element with the same number of protons, but a different number of neutrons, therefore a different mass number
(Isotopes of the same element have identical chemical properties because they have identical electronic configurations)
Relative atomic mass (Ar)
The weighted mean mass of an atom of an element relative to 1/12th of the mass of an atom of carbon-12 which has a mass of 12
Relative isotopic mass
The mass of an atom of an isotope of an element relative to 1/12th of the mass of an atom of carbon-12 which has a mass of 12
m/z
Mass to charge ratio
In mass spectrometry, nearly all ions will have lost one electron, making them +1 ions, but …
If a 2+ ion is formed, m/z = m/+2, so the m/z value is halved
Molecular ion peak (/parent ion peak)
The peak with the highest m/z ratio in the mass spectrum (the M peak). This gives the Mr of the whole molecule.
(It is the last peak (apart from the M+1 peak if visible - very small))
However, the molecular ion peak is also sometimes quite small
Orbital
A region of space within an atom where there is a high probability of finding an electron. It can hold up to two electrons with opposite spins.
(Orbitals increase in size as they move further away from the nucleus (higher quantum shells))
Aufbau Principle
Type of electronic configuration notation (s,p,d,f)
Subshells of lowest energy are filled first
Hund’s Rule
States that electrons will occupy the orbitals singly before pairing takes place.
Type of electronic configuration notation (s,px,py,pz…)
(Eg. P orbital on the x-plane/ axis)
Pauli Exclusion Principle (box notation)
States that two electrons cannot occupy the same orbital unless they have opposite spins.
Type of electronic configuration notation (boxes with half arrows - up,down)
Periodicity
The repeated trend in properties across a period
(Electronic configurations, atomic radii, melting + boiling temperatures, first ionisation energy)
Atomic radius
Distance from centre of nucleus to boundary of electron cloud
Quantum shell
Defines the energy level of an electron.
Electrons in the first quantum shell/energy level have the lowest energy (energy of electrons increases as they go further away from the nucleus)
S-block element
Has highest energy electron in an s-orbital
P-block element
Has highest energy electron in a p-orbital
D-block element
The d-sub shell is being filled
(Cannot be defined in same way as other blocks as the 4s subshell will be filled before the 3d subshell, so has more energy than the 3d subshell. Therefore the highest energy electron is not in the d subshell)
What’s the difference between relative molecular mass and relative formula mass?
Relative molecular mass is the sum of Mr of simple molecules (eg. N2, H2SO4)
Relative formula mass is the sum of Mr of compounds with giant structures (eg. Pb(NO3)2)
M+1 peak
A very small peak that sometimes occurs after the M-peak - caused by the presence of carbon-13 (isotopes)
Base peak
The tallest peak, the most abundant molecule/atom in a sample
Isomer
Compounds with the same molecular formula but with a different arrangement of atoms in the molecule and different properties
Geometric isomerism
Compounds with a C=C double bond with atoms/ groups attached to it at different positions (E/Z, cis/trans)
Crude oil
A mixture of mostly alkanes of different chain lengths and therefore different boiling points
Cracking
The process of breaking excess heavier hydrocarbons into smaller, more useful compounds
Large alkane —> Smaller alkane + alkene (with aluminium oxide catalyst Al2O3)
Reforming
Converting straight chain hydrocarbons into branched and/or cyclic hydrocarbons for efficient combustion
Carbon neutral
No NET release of carbon dioxide into the atmosphere (eg. The rate of carbon released from combustion = to the rate of carbon dioxide taken in by plants through photosynthesis)
Heterolytic fission
Unequal sharing of the electrons in the covalent bond when it breaks to form one +ve ion and one -ve ion (both electrons shift to one of the atoms - shown by full arrow head)
Homolytic fission
Equal sharing of the electrons in the covalent bond when it breaks, resulting in free radicals (shown by half arrow heads)
Sigma bond
A covalent bond formed when electron orbitals overlap end-on (stronger)
Pi bond
A covalent bond formed when electron orbitals [p-orbitals] overlap sideways (weaker) forming two regions of negative charge (above and below the sigma bond)
Note: a double bond is made up of a sigma bond and a pi bond
Electrophile
An electron PAIR acceptor
—> An electron-deficient chemical compound (or atom) that is attracted to electrons and tends to accept pairs of electrons (eg. Positive ion, delta +)
Carbocation
An ion with a positively charged carbon atom within in
Primary carbocation
The carbon with the positive charge is bonded to only one other carbon (least stable)
Secondary carbocation
The carbon with the positive charge is bonded to two other carbon atoms (more stable)
Tertiary carbocation
The carbon with the positive charge is bonded to three other carbon atoms (most stable).
Markovnikov’s Rule
In electrophilic addition, the H (or Br/Cl for diatomic) (ie. The first atom of the molecule to bond), will bond to a carbon so that the most stable carbocation can form (ie. Joins to the carbon with the least carbons attached)
This will form the major product. A minor product is formed when the most stable carbocation is not formed.
Primary halogenoalkane
The carbon which carries the halogen atom is only attached to one other carbon atom (same concept for secondary and tertiary)
Nucleophile
An electron PAIR donor
—> an atom/ion with a lone pair, (or delta -) which is attracted to areas of slightly positive charge or electron deficient atoms
Hydrolysis
Breaking up a substance using water (eg. Nucleophilic substitution with OH-)
Nucleophilic substitution
A reaction in which an attacking nucleophile replaces an existing atom or group in a molecule
Elimination reaction
A reaction in which a molecule loses atoms (H and X) attached to adjacent carbon atoms forming a C=C double bond. (The OH- acts as a base, not a nucleophile in this case)
Infrared spectroscopy
The process of using infrared radiation to determine certain bonds present and therefore the functional group. The bonds absorb the radiation causing them to vibrate
