Chem flashcards

Atomic Number

the number of protons in the nucleus of an atom

Atomic mass

the combined weight of the protons and neutrons within the nucleus

atomic radius

the distance from the centre nucleus to the outermost electron

electronegativity

the property of an atom to attract an electron when forming a bond

electron affinity

the measure of energy released when an atom in a gaseous state gains an electron

relative atomic mass definition

The ratio of the average mass of the atom to 1/12 the mass of carbon 12 atom

relative atomic mass simplified

the average mass of all the isotopes of an atom and the atomic weight in the periodic table 

Isotopes

atoms of an element with the same number of protons but different neutrons.

mass spectrometer

an analytical instrument used to accurately determine the atomic mass by separating atoms or molecules according to their charge and mass

ground state

When all the electrons are in their lowest energy level

excited state

when an electron absorbs energy causing it to jump to a higher energy level

how electrons emit light

when electron return to ground state they release the energy that was absorbed in the form of a photon

Ionisation

process of creating charged atoms

excitation

process where atoms absorb energy without being ionised 

emmission

when an electron falls and energy is released

spectrum

A range of colours is observed when white light is dispersed through a prism.

continuous spectrum

when all the wavelengths are present

emission spectrum

when certain wavelengths are emitted

absorption spectrum

when certain wavelengths are absorbed by a filtering device between the element and the observer

Emission spectroscopy

separates the light emitted into its component wavelengths when an excited state atom returns from ground state

Atomic absorption spectroscopy

technique used to determine the number of several metals in mixtures by absorbing light from excited electrons

flame test

technique used to identify what metal ion is present in a pure sample, by observing what colour flame is produced and comparing it with the flame colour set standards

limits to flame test

not accurate to identify metals in a mixture, non-metals don’t emit visible light, many metals produce similar flame colours

factors for flame colours

amount of excited electrons, the difference in movement between shells, different radiation wavelength

Ionic bond

Bond formed between non-metal and metal whose atom need to lose or gain electrons to achieve a full valence shell

cation

positvely charged Ion

Anion

negatively charged Ion

properties of Ionic compounds

• Very high melting point

• Very brittle

• Dont conduct when solid

• Insoluble in non polar solvents

Covalent Bonding

Bond where non metallic ion need to share electrons

octet rule

atoms will try to get a full set of eight electrons

covalent network

many atoms joined together in a regular array by a large number of covalent bonds

allotrope

same element with different physical structure

diamond, silica

High melting point, very strong, non conductor

graphite

High melting point, soft, conductor

nanomaterial

Substances that are composed of single units that exist in the nanoscale, 1-100nm

metallic bonding

bonds between metals where postive ions are surrounded by a sea of electrons

properties of metalic bonding

• good conductor

• malleable and ductile

• high melting point

Homologous

mixture with regular composition

Heterogenous

mixture with irregular composition

Polymers

Long chains formed when smaller molecules react with each other

immiscible

when liquids do not mix with each other

Magnetic separation

when substances are separated by magnetism

Centrifugation

when substances are separated by rotating

Decantation

separation by gravity

flocculation

when flocculant is added to mixture to coagulate small particles

filtration

uses porous barrier to separate substances

recrystallisation

separate solids by allowing them to form crystals

Distillation

uses boiling points of substances to separate

Enthalpy

measure of stored chemical energy in a chemical substance

Enthalpy change

the difference in energy from the start to end of a reaction

Exothermic

when a reaction releases energy into the surroundings

Endothermic

when a reaction absorbs energy from the surroundings

activation energy

energy needed to break reactant bonds

Fuel value

amount of energy released when a specific amount if fuel is completely combusted

Hydrocarbon

Organic compound made only of hydrogen and carbon.

Structural Isomer

Same molecular formula, atoms are connected differently.

Geometric Isomer 

same structure and connectivity, different spatial arrangement.

Hydrocarbons properties

insoluble in water, Low melting/boiling points, undergo combustion

Aliphatic Hydrocarbon

Straight or branched-chain hydrocarbons 

Alkane

Saturated hydrocarbons which, undergo halogenation by substitution with UV light.

Alkene

Unsaturated hydrocarbons with one or more double bonds

Alkyne

Hydrocarbon with at least one triple bond

Cyclic Hydrocarbon

Ring-shaped, unsaturated hydrocarbon

polar

symmetrical and equal in electron density

non polar

asymmetrical and unequal electron density

London dispersion

force found in all molecules

Dipole-DIpole interactions

occurs between polar molecules in addition to dispersion

Hydrogen bond

occurs between polar molecules where H is bonded to F, O or N

chromatography

collective term for a set of laboratory techniques for the seperation of mixtures

stationary phase

solid with high surface area which attracts components of a mixture

mobile phase

solvent that carries the mixture of chemicals

HPLC

high sensitivity method used to separate non-volatile, thermally unstable polar substances

GC

high sensitivity method used to seperate volitile, thermally stable at high temperature substance

main assumptions about ideal gas

include that gas molecules are in constant random motion, have negligible volume, and experience no intermolecular forces.

pressure

collisions of molecules with the walls of the container

boyles law

at constant temperature, the volume of gas is inversely proportional to the pressure

charles law

at constant pressure, the volume of a fixed quantity of gas is proportional to its absolute temperature

gay lussacs law

at a constant volume, the pressure of the gas is proportional to its absolute temperature

ideal gas law

PV = nRT