Definition list Flashcards
Atomic Number
the atomic number of an atom is the number of protons present in the nucleus of an atom,
MASS NUMBER
The mass number is the number of protons plus neutrons in the nucleus of an atom.
ISOTOPES
isotopes are atoms of the same element that have the same atomic number but different mass numbers
due to the different numbers of neutrons present in the nucleus.
RELATIVE ATOMIC MASS
the average mass of an atom of an element compared to 1/12 the mass of the carbon –12 isotope, taking
relative abundances of isotopes into account.
RELATIVE MOLECULAR MASS
the average mass of a molecule of a compound compared to 1/12 the mass of the carbon – 12 isotope,
taking relative abundances of isotopes into account.
RADIOACTIVITY
is the spontaneous disintegration of the nucleus with the emission of α,β or γ radiation.
NUCLEAR REACTION
a nuclear reaction involves a change in the nucleus of an atom and a new element is usually formed as a
result.
CHEMICAL REACTION
– a chemical reaction involves electrons being shared or transferred from on atom to another – the nucleus
of the atom remains the same
HALF-LIFE
this is the time taken for half the nuclei in a given sample to decay.
HEISENBERG’S UNCERTAINTY PRINCIPLE
This states that it is impossible to know both the position and the speed of an electron at the same time as
electrons move in a wave motion
ATOMIC ORBITAL
an atomic orbital is a region in space around the nucleus of an atom in which there is a high probability of
finding an electron
ENERGY LEVEL
is the discrete amount of energy an electron has when it is in an atom
TRANSITION ELEMENT
an element that forms at least one ion with a partially filled d- sublevel.
D-BLOCK ELEMENT
an element whose highest energy electron occupies a d- sublevel.
AUFBAU PRINCIPLE
electrons occupy the lowest available energy level
HUNDS RULE OF MAXIMUM MULTIPLICITY
when two or more orbitals of equal energy are available (i.e. 2px 2py 2pz ), electrons fill them singly
before filling them in pairs
PAULI EXCLUSION PRINCIPLE
no more than two electrons can occupy an orbital and this they can only do if they have opposite spin
FIRST IONISATION ENERGY
this is the minimum amount of energy required to remove the first most loosely bound electron from a mole
of isolated atoms of an element in its neutral gaseous ground state.
A MOLE
– a mole of a substance is that amount of it which contains the Avogadro’s constant number of particles
AVOGADRO’S CONSTANT
– is the number of carbon atoms in exactly 12 grams of the C-12 isotope. This equals 6×10²³ particles.
AVOGADRO’S LAW
equal volumes of all gases at the same temperature and pressure contain equal numbers of molecules.
MOLAR MASS
the molar mass of a substance is its atomic mass (or its molecular mass) expressed in grams.
MOLAR VOLUME
at s.t.p. the molar volume of any gas occupies a volume of 22.4litres (22,400cm3)
LIMITING REACTANT
- the limiting reactant is the reactant that is fully consumed when a reaction goes to completion
THEORETICAL YIELD
the theoretical yield of a reaction is the quantity of product that should form when all of the limiting reactant
reacts. To get the theoretical yield use the molar ratio from the balanced equation between the limiting reactant
and product.
ACIDS- Arhenius’ theory
An acid produces H+ ions in water
MONOBASIC ACID
A monobasic acid produces one H+ ion in solution e.g HCL & HNO3
DIBASIC ACID
A dibasic acid produces two H+ ions in solution e.g H2SO4
TRIBASIC ACID
A tribasic acid produces three H+ ions in solution e.g H3PO4
BASES- Arhenius’ theory
A base produces OH- ions in water.
ACID- Bronsted-Lowry threory
- an acid is a proton (H+ ) donor
BASE- Bronsted-Lowry theory
a base is a proton (H+ ) acceptor.
