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chemistry

Continuous spectrum

Colours from red to violet formed when white light is passed through a prism

Emission line spectrum

Consists of coloured lines against a dark background, indicates the presence of energy levels in atoms.

Crimson

Flame colour of Lithium

Lilac

Flame colour of Potassium

Yellow-green

Flame colour of Barium

Red

Flame colour of Strontium

Blue green

Flame colour of Copper

Yellow / Orange

Flame colour of Sodium

Spectrometer

The instrument used to examine spectra (spectroscope)

Bohr

Scientist who proposed that electrons revolve around the nucleus in fixed paths called orbits or energy levels which are quantised, i.e. fixed at a definite amount.

Energy level

The fixed energy value that an electron in an atom may have

Ground state

Describes an electron which is in its lowest energy level

Excited state

Describes an electron which has moved into a higher energy level after it has absorbed a certain amount of energy.

E = hf

Formula to show that the definite amount of energy emitted from atom is equal to the light of definite frequency or wavelength in emission spectrum

Balmer

Series which gives rise to lines in the visible spectrum

Lyman

Series which gives rise to lines in the ultraviolet of the spectrum

Paschen

Series which gives rise to lines in the infra-red region of the spectrum

Absorption

Type of spectrum produced when white light is passed through a gaseous sample of an element.

Absorption spectrum

Consists of dark lines against a coloured background.

Atomic absorption spectrometer

Instrument which indicates the amount of light absorbed and so measures the concentration of a metal in a sample. Used in the analysis of water for heavy metals like lead, mercury and cadmium

Electronic configuration

Shows the arrangement of electrons in an atom of that element

s p d and f

4 main sublevels which are associated with the main energy levels

Aufbau Principle

States that when building up the electronic configuration of an atom in its ground state, the electrons occupy the lowest available energy level

1s 2s 2p 3s 3p 4s 3d 4p

Order in which the sublevels are filled

Cu and Cr

Exceptions to order of sublevels. Both have a half-full 4s orbital and a full or half-full 3d sublevel as this is a more stable configuration.

Orbital

A region in space within which there is a high probability of finding an electron.

s

spherical orbitals, 1 per sub-level

p

dumb-bell shaped orbitals, 3 per sub-level (x, y, z)

Hund's Rule of Maximum Multiplicity

States that when two or more orbitals of equal energy are available, the electrons occupy them singly before filling them in pairs.

The Pauli Exclusion Principle

States that no more than two electrons may occupy an orbital and they must have opposite spin.

Heisenberg's Uncertainty Principle

States that it is impossible to measure at the same time both the velocity and the position of an electron.

De Broglie

Scientist who suggested that all moving particles had a wave motion associated with them

Wave particle duality

Refers to the idea that a particle (like an electron) can behave like a wave

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