(🟠 TOPIC 1) Key Definitions …

Question 1

Atomic number (z)

Answer 1

The number of protons in the nucleus of an atom of a certain element

Question 2

Mass number (A)

Answer 2

The sum of the number of protons and the number of neutrons in the nucleus of an atom of a certain element

Question 3

Isotopes

Answer 3

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)

Question 4

Relative atomic mass (Ar)

Answer 4

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

Question 5

Relative isotopic mass

Answer 5

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

Question 6

m/z

Answer 6

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

Question 7

Molecular ion peak (/parent ion peak)

Answer 7

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

Question 8

Orbital

Answer 8

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))

Question 9

Aufbau Principle

Answer 9

Type of electronic configuration notation (s,p,d,f)
Subshells of lowest energy are filled first

Question 10

Hund’s Rule

Answer 10

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)

Question 11

Pauli Exclusion Principle (box notation)

Answer 11

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)

Question 12

Periodicity

Answer 12

The repeated trend in properties across a period
(Electronic configurations, atomic radii, melting + boiling temperatures, first ionisation energy)

Question 13

Atomic radius

Answer 13

Distance from centre of nucleus to boundary of electron cloud

Question 14

Quantum shell

Answer 14

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)

Question 15

S-block element

Answer 15

Has highest energy electron in an s-orbital

Question 16

P-block element

Answer 16

Has highest energy electron in a p-orbital

Question 17

D-block element

Answer 17

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)

Question 18

What’s the difference between relative molecular mass and relative formula mass?

Answer 18

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)

Question 19

M+1 peak

Answer 19

A very small peak that sometimes occurs after the M-peak - caused by the presence of carbon-13 (isotopes)

Question 20

Base peak

Answer 20

The tallest peak, the most abundant molecule/atom in a sample

Question 21

Isomer

Answer 21

Compounds with the same molecular formula but with a different arrangement of atoms in the molecule and different properties

Question 22

Geometric isomerism

Answer 22

Compounds with a C=C double bond with atoms/ groups attached to it at different positions (E/Z, cis/trans)

Question 23

Crude oil

Answer 23

A mixture of mostly alkanes of different chain lengths and therefore different boiling points

Question 24

Cracking

Answer 24

The process of breaking excess heavier hydrocarbons into smaller, more useful compounds
Large alkane —> Smaller alkane + alkene (with aluminium oxide catalyst Al2O3)

Question 25

Reforming

Answer 25

Converting straight chain hydrocarbons into branched and/or cyclic hydrocarbons for efficient combustion

Question 26

Carbon neutral

Answer 26

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)

Question 27

Heterolytic fission

Answer 27

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)

Question 28

Homolytic fission

Answer 28

Equal sharing of the electrons in the covalent bond when it breaks, resulting in free radicals (shown by half arrow heads)

Question 29

Sigma bond

Answer 29

A covalent bond formed when electron orbitals overlap end-on (stronger)

Question 30

Pi bond

Answer 30

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

Question 31

Electrophile

Answer 31

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 +)

Question 32

Carbocation

Answer 32

An ion with a positively charged carbon atom within in

Question 33

Primary carbocation

Answer 33

The carbon with the positive charge is bonded to only one other carbon (least stable)

Question 34

Secondary carbocation

Answer 34

The carbon with the positive charge is bonded to two other carbon atoms (more stable)

Question 35

Tertiary carbocation

Answer 35

The carbon with the positive charge is bonded to three other carbon atoms (most stable).

Question 36

Markovnikov’s Rule

Answer 36

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.

Question 37

Primary halogenoalkane

Answer 37

The carbon which carries the halogen atom is only attached to one other carbon atom (same concept for secondary and tertiary)

Question 38

Nucleophile

Answer 38

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

Question 39

Hydrolysis

Answer 39

Breaking up a substance using water (eg. Nucleophilic substitution with OH-)

Question 40

Nucleophilic substitution

Answer 40

A reaction in which an attacking nucleophile replaces an existing atom or group in a molecule

Question 41

Elimination reaction

Answer 41

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)

Question 42

Infrared spectroscopy

Answer 42

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