Atomic Structure and Electron Arrangement - Leaving Cert Chemistry

dalton’s atomic theory

all matter is made of atoms, atoms are indivisible and small, atoms cannot be created or destroyed, elements are made of one type of atom, atoms can join together to form compounds.

cathode rays

streams of negatively charged electrons which travel from cathode to anode

alpha particles

positively charged particles, used in Rutherford’s gold foil experiment

emission line spectrum

in the ground state, the hydrogen electron occupies the lowest available energy level. the electron can jump to a higher energy level if it receives a certain amount of light. this excited state is temporary and unstable. as it falls back down, energy is emitted as a photon, thus giving rise to a spectrum

energy level

a region of definite energy within the atom that electrons can occupy

ground state

the lowest energy state for an electron

excited state

when an electron occupies a higher energy state than its ground state by absorbing enough energy

sub levels

a subdivision of an energy level, containing one or more atomic orbitals, all of equal energies

uncertainty principle

it is not possible to measure both the position and velocity of an electron, since doing one affects the other.

orbital

a region in the space of an atom where the probability of finding an electron is relatively high

greeks

all matter is made of tiny particles called atoms, no experiments, four elements - earth, fire, air, water

john dalton

first to do experiments, atomic theory

william crookes

investigated cathode rays in a vacuum tube, the maltese cross experiment, the paddle wheel experiment

jj thomson

cathode rays consist of negatively charged particles, electrons, proposed the plum pudding model

george stoney

coined the term electron

robert millikin

investigated the size of the charge on the electron, oil drop experiment, charged oil drop suspended between two charged plates

ernest rutherford

gold foil experiment, most alpha particles passed through the gold foil, some were deflected at large angles, a very small amount were deflected back along their own path. the electron cloud model, the nucleus

james chadwick

bombarded beryllium with alpha particles, observed a type of radiation with no charge, the neutron

proton (charge, mass, location)

+1, 1, nucleus

neutron (charge, mass, location)

0, 1, nucleus

electron (charge, mass, location)

-1, 1/1860, space outside the nucleus

emission spectrum

The series of coloured lines of definite wavelength observed against a dark background. The emission spectrum for each element is unique to that element.

continuous spectrum

When white light is passed through a prism, the resulting continuous band of colours from red to violet is known as a continuous spectrum

line spectrum

The series of coloured lines of definite wavelength observed against a dark background.

absorption spectrum

The series of dark lines observed against a coloured background after white light has been passed through an element.

bohrs theory

electrons revolve around the nucleus in fixed paths called energy levels - while in a particular energy level, the energy of the electron is fixed - electrons normally occpy the lowest available energy level - when an atom absorbs energy, electrons jump to a higher energy level - when the electron falls back down to lower energy level, the energy absorbed is emitted as a photon of light of definite frequency - the amount of energy released is equal to the energy difference between the two energy levels - the energy emited appears as a single lne of definite colour in the emission line spectrum

limitations on bohrs theory

only worked for hydrogen - subsequent discoveries, energy sublevels, wave nature of the electron, uncertainty princple, orbitals

sublevel names

s, p, d, f

sublevel order

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

louis de broglie

wave particle duality - eletrons move in a wave like motion around the nucleus

erwin schrodinger

probability of finding an electron at a particular sublevel, orbitals

s orbital shape

sphere

porbital

dumbbell

lithium

crimson

potassium

lilac

barium

green

strontium

red

copper

blue-green

sodium

yellow