Chemistry – Physical Chemistry

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What are nucleons and where are they found?
Protons and neutrons, found in the nucleus
What is the relative charge and mass of a proton, electron and neutron?
Proton -> +1 (charge), 1 (mass)
Electron -> -1 (charge), 1/1840 (mass)
Neutron -> 0 (charge), 1 (mass)
How are protons and neutrons held together?
By strong nuclear forces
What holds electrons and protons together?
Electrostatic forces of attraction
What is the bigger number, the mass number (A) or the proton/atomic number (Z)?
Mass number>proton number
Mass number =
Relative atomic mass=
Average mass of 1 atom/one twelfth of 1 atom of carbon-12
What are the main stages of mass spectrometry?
Ion drift
Data analysis
What is the name of the energy needed to remove electrons from an atom?
Ionisation energy
Why does the first ionisation energy require the least energy?
As it is being removed from a neutral atom
What is the trend in successive ionisation energies?
The energy required increases
What is the trend in IE across a period and what is the reason for this?
Generally IE increases as the nuclear charge increases, making it harder to remove an electron
What is the trend in IE down a group and what is the reason for this?
Generally IE decreases as the outer electrons are getting further away from the nucleus, as of shielding (despite the increase in nuclear charge)
Relative molecular mass=
Mass of one molecule/one twelfth of 1 atom of carbon-12
What is the Avogadro constant?
The number of atoms in 12g of carbon-12
What is the mole?
Amount of substance that contains 6.022*10^23
What is the ideal gas equation?
What are the steps to work out the empirical formula?
Find the masses of each element and work out the moles
Divide by the smallest term
Molecular formula=
Relative molecular mass/empirical formula
*by empirical formula
Atom economy=
Mass of desired product/total mass of reactants
Yield of a reaction=
Moles of product/theoretical possible number of moles of the product
Why do atoms bond?
To achieve a more stable electron arrangement, like the noble gases
What are the 3 types of chemical bonds?
Ionic, covalent and metallic
Ionic (7)
Between metal and non-metal
+ve and -ve ions are formed which are held together by electrostatic forces
Consists as a lattice
E.G. Magnesium oxide
High mpt. and bpt. as lots of energy is required to break the strong lattice held together by electrostatic forces
Conduct electricity when molten/dissolved in water (aq)#
Brittle – when given a sharp blow like charged ions may come into contact
Covalent (6)
Between non-metal and non-metal, which share their electrons
Are neutral mmolecules
E.G. Methane
Electrons are held by electrostatic forces of attraction to the nuclei
Have weak attraction to to other molecules
Poor conductors of electricity as there are no charged particles, however some can if they dissolve in water
What is dative covalent bonding and what is it’s other name?
When one electron donates a lone pair to a electron deficient atom
Also known as co-ordinate bonding
How is co-ordinate bonding represented?
Using an arrow pointing to the atom receiving the electron pair
How strong are co-ordinate bonds compared to covalent bonds?
Have the same strength and length
Metallic (6)
Between metals, which consists of a lattice of positive ions existing in ‘sea’ of electrons
Forms giant structures
Conduct heat and electricity – have free electrons – when one electrons joins from the negative terminal, one electron leaves from the positive terminal
Strength of metal depends on charge on ion – more electrons and the size of the ion – close to e-
Malleable and ductile as after each distortion they are in the same environmetn
High melting point – large structure = hard to breaj
Define electronegativity
the power of a species to attract the electron density in a covalent bond towards itself
What does electronegativity depend on?
Nuclear charge
Distance between nucleus and the outer electrons
How is electronegativity measured?
By the Pauling Scale, 0-4
Trends in electronegativity
Increases up a group – as atoms get smaller and shielding decreases
Increases across a period – as nuclear charge increases and atoms become smaller
What is the most electronegative element?
Flourine (F)
What are the 3 types of intermolecular forces? (from weakest to strongest)
Dipole-dipole forces
Hydrogen bonding
What are H-bonds between?
H and NOF
What shape do H-bonds have?
What is the strength of a H-bond?
10% of a covalent bond
What happens when water freezes?
Water molecules are no longer free to move and are held in place by the hydrogen bonds.
In order, to fit the ice structure, the molecules are slightly less packed closely so ice is less dense than water.
So, in lakes ice forms at the top, which insulates the pond allowing fish to survive in the cold
Pair of 2 electrons
Linear, 180°
Pair of 3 electrons
Trigonal planar, 120°
Pair of 4 electrons
Tetrahedron, 109.5°
Pair of 5 electrons
Trigonal bipyramid, 120° + 90°
Pair of 6 electrons
Octahedron, 90°
Repulsion between electron pairs (inc. order)
Bonding – bonding pair
Bonding – lone pair
Lone – lone pair
Name the 4 types of crystals
Simple molecular
Categories: Physical Chemistry