Grade 12 Chemistry

1) Atoms of different elements have different properties 2) Law of definite proportion and multiple compositions: atoms of 2 or more elements can combine in a fixed ratio to form new substances depending on their combining capacities (eg. H2O vs H2O2) 3) Law of conservation of mass

1) he said atoms cannot be divided, but they can - electrons, neutrons and protons2) he said that all atoms of the same element have the same mass- but there are isotopes

Thompson used a cathode ray tube and found that the positive ray was attracted towards the positive object, meaning that atoms consist of something negatively charged - proposing an atom positively charged with electrons embedded within

It was an experiment that helped to determine the size and charge on an electron, the charge on a single electron was 1.6 x 10^19

He did the gold foil experiment, he shot positive particles at a gold foil, expecting them all to go through, but some deflected, he concluded that there must be a concentrated nucleus, with electrons surrounding it

He was calculating the mass of a specific nuclei, and the mass the got didn't match with the associated charge of the electron, therefore he knew there must be neutral particles making up the missing mass- neutrons

If electrons are travelling in a circular orbit, they are constantly changing direction, meaning they are accelerating, meaning they should emit electromagnetic radiation, lose electrons, and collapse eventually

He suggested that energies of vibrating atoms were multiples of small quantities of energy (energy was not continous). Atom must absorb or release an antire quanta of energy or none at all, thers no "in between"

When an atom releases energy, it does it in a form of light, the hotter the atom, the smaller the wavelength, more the energy

When there is light shone on a metal surface, electrons release from the surface of the metal, the number of electrons per second can be measured by a ammeter. Frequency determines the how fast they jump, and intensity determines how many electrons. Electrons only jump is the frequency is at a specific pt. Higher frequency means high energy

He put planck's idea together with the photoelectric effect. So if one electron absorbs one photon (quanta of energy), it must be great enough for the electron to escape, the rest of the energy is left over

A photon is a packet of energy that corresponds to the frequency of the electromagnetic wave. E= hf, f stands for frequency and h stands for planck's constant- 6.6 x 10^34

Spectroscopy was invented by Robert Bunsen and Gustev Kirchhoff in the 1850s to study light. When white lights passes through a spectroscope, the light is divided into a rainbow of colours (continous spectrum)

A display of all colours- dispersion (refraction) of white light through a prism

Certain colours are missing from a display of colours produced by white light. Phonton absorbed when electrons jump from lower energy to a higher energy state. Helping scientists to identigy the gas the light passed through