AS化学常考定义分享 这些英文版的定义更值得记忆

秋季大考就在眼前了，下面来给大家分享一些有关AS化学常考定义，这些定义都是英文版本的，希望大家都能够早日熟悉这些专业用语啊！

standard enthalpy change of combustion

the enthalpy/energy change when one mole of a substance

is burned in an excess of air/oxygen or completely combusted

under standard conditions 

activation energy

the minimum energy  required

in order for the reaction to take place

acid

A proton(H+) donor

weak acid

(an acid that is) partially / incompletely ionised/ dissociated

dynamic equilibrium

an equilibrium which forward reaction rate quals backward reaction rate or forward/back reactions occurring but concentrations of all species do not change

isotope

atoms with the same number of protons

but different number of neutrons

strong acid

(an acid that is) completely ionised/ dissociated

relative atomic mass

average mass of an atom of an element

compared with C -12

one atom of C-12 has a mass of exactly 12

chiral centre

chiral centre is a carbon  atom that bonds to four different groups or atoms 

first ionisation energy

Energy required to remove one mole of electrons

from  one mole of gaseous atoms of an element  

Relative isotopic mass

Mean/average mass of  an atom relative to 1/12 the mass of an atom of C-12 

Isotope

Atoms with the same number of protons and different number of neutrons 

Atomic number 

Proton number or number of protons 

Mass number

Nucleon number; total number of protons and neutrons 

First ionisation energy 

The amount of energy required to remove one electron from each atom in one mole of atoms of the element in the gaseous state (to form gaseous 1+ ions). 

Ionic bonding

Attraction/attractive force between positively and negatively charged ions in an ionic lattice. 

Covalent bonding

Attraction between nucleus and shared pair of electrons. 

Dative covalent bonding

One atom provides both electrons in the formation of the covalent bond. 

Sigma bond (σ bond）

Sigma bonds are formed by end-on overlap of atomic orbitals. 

Pi bond (Π bond）

Pi bonds are formed by sideways overlap of p-type atomic orbitals. 

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