Unit 1: Foundation chemistry Flashcards
what is the mass no.?
total no. of protons and neutrons in the nucleus of one atom of the element
Define ionisation energy
Energy required to remove a mole of electrons from a mole of atoms in the gaseous state
Measured in kJ mol-1
what is the atomic no.?
no. of protons in the nucleus of one atom of the element
state the 3 main fundamental particles and their mass and charge
particle, relative mass, relative charge:
proton , 1, +1
neutron, 1, 0
electron, very small 1/1840, -1
Define relative atomic mass
Weighted average mass of all isotopes divided by 1/12 mass of one atom of carbon-12
Average mass of an atom/isotope on a scale where an atom of C12 had a mass of exactly 12g
Define structural isomers
Compound with the same molecular formula but a different structural formula
Identify a catalyst used in a catalytic converter
Iridium or Platinum or Palladium or Rhodium
Hazards associated with the product solid carbon in combustion
Global dimming Exacerbates asthma Damages lungs Breathing problems Smog/smoke etc.
Relative molecular mass
Average mass of one molecule divided by 1/12th of mass of an atom of C12
Mass of a molecule on a scale whee the mass of C12 is exactly 12g
Avogadro constant
Total number of particles in a mole of substance
No. Of atoms in 12g of carbon 12
6.022 x 10^23 atoms = mole
Electro negativity
Power of an atom to attract the electron density in a covalent bond towards itself
Describes the way negative charge is distributed in a molecule
Bond angles and shape names
Linear 180 Trigonal planar 120 Tetrahedral 109.5 Trigonal bipyramidal 120 and 90 Octahedral 90 Square Planar 90 Additional 2 per lone pair
Bond angles for water H20 and ammonia NH3
Water 104.5
Ammonia 107
Due to 2 extra per lone pair
Atomic radii definition
Half the distance between the centres of a pair of atoms
Atomic radii trends
Decrease across a period - increased nuclear charge, same shielding, pulls electrons closer to nucleus
Increase down a group - increase in main level of electrons, outer electrons get further from nucleus
General First ionisation energy trends
Increases across a period - increasing nuclear charge, same distance, same shielding, harder to remove electrons
Decreases down a group - increase in shielding, increased distance, held less strongly, easier to remove electrons
Why do we assume that there are the same number of protons and electrons in an atom?
In a neutral atoms the number of electrons must be the same as the number of protons because their charge is equal in size and apposite in sign
Isotope definition
Atoms with the same number is protons but different number of neutrons
Different mass numbers but same atomic number
Explain why the ions formed in a mass spectrometer have a positive charge
Because they have lost electrons which are negatively charged
What causes ions to accelerate through the mass spectrometer?
Positive ions are Attracted by a negatively charged plate
What forms ions into a beam in mass spectrometry?
The ions pass through a series of holes or slits
What bends the ions into a curved path in mass spec?
A magnetic field at right angles to their direction of motion
What is the Schrodinger equation?
Solutions to this equation give the probability of finding an electron in a given volume of space called an atomic orbital
What is activation energy?
Minimum energy that a particle needs in order to react the energy (enthalpy) differed between the reactants and the transition state
Define aldehyde
An organic compound with the general formula RCHO in which there is a Cā0 double bond
Define alkanes
A hydrocarbon with C-C and C-H single bonds only.
General formula CnH2n+2
Define allotropes
Pure elements which can exist in different physical forms in which their atoms are arranged differently
E.g Diamond, Graphite, Buckminsterfullerence are allotropes of carbon
Percentage Atom economy definition and equation
Describes the efficiency of a chemical reaction by comparing the total number of atoms in the product wit the total number of atoms in the starting materials
= mass desired product/total mass of reactants x 100
Define atomic orbital
A region of space around an atomic nucleus where their is a high probability of finding an electron
