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.

ligand

an ion or molecule attached to a metal atom by dative bonding (e.g Water)

Properties of metallic bonding

• Good conductors due to delocalised/free electrons

• malleable and ductile due to the shiftable arrangement of particles

• Lustrous

• High melting pong and malleability due to strong forces between lattice bonds

• Giant metallic structures

• Electrostatic attraction

properties of Ionic bonding

• Electrostatic attraction

• solid at room temperature

• Giant structures

• High melting points

• Crystalline

• Brittle - shatter easily as ions of the same charge become adjacent

• Conductors in liquid or solvated state

• metals & non-metals

Properties of Covalent bonds

• Non-metals & non-metals

• molecules are neutral

• electrostatic forces

• Low melting and boiling points

• often amorphous (no definite form)

• Remain molecules if dissolved in water

• poor conductors of electricity

Lone pair

2 unpaired elctrons - can partake in dative bonding, sometimes form dimers

London dispersian forces ( Van der Waals)

A temporary attractive force that results when the electrons in two adjacent atomcs occupy postitions that make the atom form temporary dipoles

electric dipoles

arise from opposite but equal charges seperated by distance

Conditions for Hydeogen bonding

• A hydrogen ato covalently bonded to an electronegative atm (N, O or F)

• A lone pair of electrons on the electronegative atom

Latent heat of fusion

The amount of heat required to convert a unit mass of solid into liquid without a change in temperature

Latent heat of Vapourization

The amount of heat required to convert a unit mass of liquid into vapor without a change in temperature

allotropes

different arrangements of the same elements, in the same state. e.g Diamond and graphite.

Where are giant covalent bonds found

Molecules and macro molecules

Where are Ionic (electrostatic) bonds found?

Regular lattice structures of Ionic compounds. mostly soluble in polar sovlents

Where are Simple covalent bonds found?

covalently bonded atoms.

Where are Metallic bonds found?

3D lattice bonding in which the delocalised valence electrons are attracted to the surrounding cations

What is the Relative strength of Giant covalent bonds?

Strongest (Very strong)

What is the relative strength of Ionic (electrostatic) bonds?

Second strongest (but not by much)

What is the Relative strength of Simple covalent bonds?

Weakest

What is the Relative strength of metallic bonding?

Strong (second weakest)

What are Giant covalent bonds based on?

The Stable balance of attractive and repulsive forces between atoms which share valence electrons

What are Ionic (electrostatic) bond based on?

Electrostatic attraction between oppositely charged ions in a regular lattice structure

What are Simple covalent bonds based on

Weak Van der Waals forces in between covalently bonded molecules

What are metallic bonds based on?

Attraction between free valence electrons and the nuclei of neighbouring metal atoms

How are sigma (σ) bonds formed

by direct overlap of orbitals between the boning atoms

How are Pie (π) bonds formed

by the sideways overlap of adjacent p orbitals

Hybrid orbtals

Orbitals formed by mixing of atomic orbitals

What does VSEPR stand for

Valence shell electron pair repulsion

What does the VSEPR model mean

To minimise repulsion by maximising seperation

2 bonding pairs, 0 lone pairs

linear

3 bonding pairs, 0 lone pairs.

trigonal planar

2 bonding pair, 1 lone pair

bent I

4 bonding pairs, 0 lone pairs.

tetrahedral