Chem Vocab

As Chemistry

Systematic error

error due to the equipment accuracy or set up, ‘consistent’, cannot be averaged out

Random error

caused by human ability, different each time, can be averaged out, given by half the smallest division.

Accuracy

How close results are to the true value

Precision

a measure of how consistent you can be with your measurements

Tables should:

• Plan the correct number of columns and rows to avoid adjustments later.

• Use a ruler to create neat, straight lines.

• Label columns and rows clearly with quantities and units (e.g., Temperature / °C) using slash notation to keep table values unitless.

• Maintain consistency in significant figures.

• For calculated differences, include initial, final, and difference values.

• Add columns for simple conversions, like inverting or scaling.

no. of moles

m/M

Enthalpy change

-Energy/no. of moles

Unified atomic mass

the mass of one-twelth of the mass of a carbon 12 atom

Mole

the amount of a sumstance that contains the same number of stated elemtary units as there are atoms in 12g of Carbon-12

Relative molecular mass

the weighted average mass of a molecule in a given sample of that molecule compared to the vlue of the unified atomic mass

Relative formula mass

the weighted average mass of one formula unit compared to the value of the unified atomic mass

Relative atomic mass

the weighted average mass of atoms in a given sample of an element, compared to the value of the unified atomic mass

Relative isotopic mass

the mass of a particular atom of an isotope compared to the value of the unified atomic mass

Isotope

atoms of the same element which have the same atomic number nut different mass number

Heisenberg Uncertainty model

Everything we do affects the electrons so we cannot know both the speed and position at the same time

Relative abundance

different isotopes weigh differently - when one isotope is is more abundant, the relative atomic mass will be closer to that isotopic weight

mass spectometre

ionizes atoms and then sends them through an electromagnetic field where they are deflected on the basis of their mass and charge

Volatility

how easily a substance vaporizes

Ionization energies

the energy needed to remove 1mol of electrons from 1mol of atoms

Factors that affect ionization energy

• less electrons in outer shell = less ionization energy (Nuclear Attraction)

• more shells = less ionization energy (electron shielding)

  • bigger atomic radius = less ionization energy

Elastic collision

all energy is transfered

Inelastic collision

energy is lost (e.g through heat) during a collision

Ideal gas Law

a gas whose volume varies exactly in proportion to the temperature an exactly in inverse proportion to the pressure

R

Gas constant (8.31JK^-1mol^-1)

To convert to Kelvin

+237.15^o

avagadros constant

6.02 × 10²³

principle quantam number

number of shells

free radical

a species with one or more unpaired electron

Paul’s eulsion principle

No orbital may contain more than 2 electrons, the elctrons may not have the same spin.

Hund’s rule of ‘maximum mutiplicity’

when in orbitals of equal energy, electrons will try to remain unpaired

Aufbau (buildup principle)

electrons enter the lowest available energy level

molar second ionization energy

the nergy needed to remove one mole of electrons from one mole of gaseous plus 1 ions.

emperical formula

the simplest whole number ratio of atoms present in a compound

molecular formula

shows the exact number of molecules present

Atomic radius

As the Atoms get bigger, the valence electrons are further away and require less energy to be taken off.

Electron shielding

As atoms gain shells the inner electrons repel the outer electrons and the ionization energy decreases

Nuclear Attraction

the greater the number of protons in the nucleus, the greater the attractive forces on the outer electrons and therefore the greater the ionization energy.

fragmentation

the process in which a molecular ion breaks into smaller ions, radicals and/or neutral molecules.

free radical

a species with one or more unpaired elctrons

gas constant

8.31JK^-1mol^-1

To convert from degrees celsius to Kelvin

+273.15

Combustion formula

H_xC_y + (x+y/4)O₂ → xCO₂ + y/2H₂O

Ideal gas Law formula

PV = nRT

electronegativity

The ability of an atom in a molecule to attrcat bonding electrons in a covalent bond to itself

Ionic bond

metal & non-metal - Electron transferred. Full charges on atoms

Nonpolar Covalent bond

Bonding lectrons shared equally between two atoms. No charges

Polar covalent bond

Bonding electrons shared unequally between two atoms. Partial charges on atoms

The pauling scale

measure electronegativity

Trend in Elctronegativity

Increases from bottom left to top right

avogadros constant value

6.02×10²³

electronegativity difference of less than 0.5

bond type: pure Covalent

Electronegativity difference between 0.5 and 1.6

Bond type: polar covalent

Electronegativity difference 1.6 - 2.0 ( + a metal)

bond type: ionic

avogadros constant

the amount of particles in a mole

NO₃^-

Nitrate

CO₃^2-

carbonate

SO₄^2-

sulfate

OH^-

Hydroxide

NH₄⁺

ammonium

Zn²⁺

Zinc

Ag⁺

Silver ion

HCO₃^-

bicarbonate ion

PO₄^3-

Phosphate

covalent bond

Non-metals react together, share electrons to gain full outer shells, there is electrostatic attraction between their nuclei

electron deficient

a compound in which the central atom’s octet is stable without complete octet. Boron, Beryllium, aluminium.

Expanded octet

Atoms from periods 3 or above expand their octet by moving s or p electrons into the d orbital

Dative covalent vond

one species donates a lone pair f electrons to another atom or ion.

Dimer

a molecule or molecular complex consisting of two identical molecules linked together.