AQA AS Level Chem Unit 1 Defintitions

number of protons (Z / proton number)

no units

Number of protons and number of neutrons

no units

Atoms with the same numer of protons but a different number of neutrons.

• Different isotopes of the same element react chemically in the same way
• Vary in mass number due to the different amount of neutrons

An instrument used to measure the relative atomic mass (RAM) on a scale based on the mass of an atom of Carbon-12 which has a RAM of 12

A beam of electrons, fired from an electron gun, knocks an electron from an atom to create positive ions

Norally only one electron is removed creating a 1+ charge, but occasionally two electrons are removed creating a 2+ charge

The postive ions are attracted towards negitivly charged plates and accelerated to a high speed

The lighter the ion, the faster they go

The beam of ions moves into a magnetic field, at right angles to it's direction of travel. The magnetic field deflcts the ions.

The amount of deflection depends upon the m/z vaue of the atoms, the charge mass ratio. As the charge, in most cases is 1, the deflection depends solely upon the mass number.

• 2+ ions are deflected twice as much

Ions hit the detector, accept electrons, lose their charge and create a current which is proportional to the abundance of each ion.

A graph showing the relative abundance (y-axis) and mass/charge value (x-axis) produced by the mass spectrometer

Relative atomic mass:

(m/z value x % abundance) + (m/z value x % abundance)

100

watch out for 2+ ions, as they may obscure your result

Used on space probes, eg. Viking Martian, to identify the elements in rock samples on other planets/moons/comets in space.

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5d6

• Two electrons in the same orbital have opposite spins
• Represented by an arrow pointing up or down, depending on direction of spin

The energy required to remove one mole of electrons from a mole of atoms in the gaseous state.

measured in Kj/mol

The first IE needs the leas energy to remove

The secnds needs more energy than the first beacuase it is being removed from a 1+ ion

and so on..

The average mass of one atom of an element

1/12th mas of one atom of Carbon-12

average mass of one molecule

1/12 the mass of one atom of Carbon-12

The number of atoms in 12 g of Carbon-12

6.022x10^23 or mole

Moles = mass in g / RAM

V is proportional to T

or using a constant (k):

• V= kT
• T=kV
• k=V/T

PV/T = constant for a fixed mass of gas.

(as PV= k and V/T = k)

PV = nRT

The simplest ratio of the atoms of each element present in a compound

To find empirical formula:

• Find the masses of each element
• Find the moles using moles = mass / ram
• convert moles into whole number ratio

The actual number of atoms of each element present in a compound.

To find molecular formula from empirical formula:

• units of empirical formua: relative molecular mass / relative mass of empirical formula
• times the empirical formula by the units

eg. CHv2 has a relative molecular mass of 12 and relative mass of 24

24 / 12 = 2

2 x 2 = 4 so molecular mass = Cv2Hv4

Concentration= number of moles / volume in dm^3

NB- if given in cm^3 divide by 1000

Atom economy = (mass of disired product / total mass of reactants ) x100

Used to determin how much of the reactants will be wasted and if the experiment is useful, cost effective and sustainable.

Percentage yield = (the number of moles of a specified product / theoretical maximum number of grams of the product) x100

• Between a metal and a non-metal
• Electrons are transfered from metals to non-metals
• Positive and negative ions are formed
• Electrostatic forces hold the ions together

• Soild at room temperatures
• Giant structures
• High meltin temperatures
• Conduct electricity when molten or disolved in water
• Brittle
• Shatter easily

• A bond between a pair of non-metal atoms
• Share the outer shell electrons
• Two atoms share one pair of electrons

Occasionaly double covelent bonds are formed, when two atoms share two pairs of electrons. Called a double bond.

A single atom provides both the electrons in the shared pair. This can be called a dative covalent bond

• The atom that accepts the pair is an atom that doesn't have a filled outer level of electrons, this atom is deficient
• 
• The atom doning the electrons has a pair of electrons that is not involved in a bondm called a lone pair

The power of an atom to attract the electron density in a covelent bond towards itself. It depends upon:

• thenuclear charge
• the distance between the nucleus and the outer shell electrons
• the shielding of the nuclear charge by the electrons in the inner shells

A lattice of positive ions in a sea of outer electrons.

• Giant structures
• Malleable and ductile
• High melting points- strong bonds

Forces that act between molecules.

• van der Waals
• Dipole-dipole
• Hydrogen bonding

An intermolecular force that results from the attraction between molecules with permenent dipoles.

• 2nd weakest intermolecuar force

All atoms and molecules have positive or negative charges, even if neutral overall. These charges produce a very weak electrostatic attractions.

• The distribution of the charge changes every second
• In addition to other forces

The weakest intermolecular force

When a hydrogen atom is bonded to a very electronegative atom:

• Oxygen
• Nitrgoen
• Fluorine

The strongest intermolecular force

A saturated hydroarbon containing no double bonds.

An orgainic compound containing one or more double bond.