p1.1 - The particle model Flashcards
what does the word “atomos” mean in greek
indivisble
who first thought of the atom
democtirus and leucippus
what was daltons model
in 1870, dalton did experiements to measure how elements combined. His model was a very small indestructible sphere
what did dalton assume
All the atoms in an element are the same
The atoms in one element are different from the atoms in all other elements
what was thompsons model
in 1897, thompson was investigating rays given out by hot metals called cathode rays.
he discovered that cathode rays are made of particles that have less than one thousandth of the mass of a hydrogen atom.
what did thompson discover
he found a praticle which he called an electron that must have come from inside the atom. He worked out the charge was negative
what ideas did he make sense of, or the structure of the atom.
An atom contains negative electrons
overall, atoms have no electrical charge. They are neutral
what was thompsons model
he said that atoms are like “pulm puddings” and then created his own model of the atom. in this model the atom is thought to consist of positive mass with negative electrons embedded in it. he did not know what the positive mass was made of
what was rutherfords model
in 1889 ernest rutherford discovered that some materials emit particles. he called them alpha particles.
what was rutherfords gold foil epxirement
rutherford fired alpha particles at a piece of gold foil. wat he noticed was that some particles came back when fired. he concluded that an atom is made of a tiny positively charged nucleus and when alpha particles hit a nucleus, they bounce back. later, scientists discovered the nucleus is made of two different types of particle, which they called protons and neutrons
what is the bohr model
the issue with thompsons model was that you would expect the electrons to spiral unti they hit the nucleus. in 1913, bohr suggested that electrons can only move in fixed orbits, called electron shells around the nucleus. the bohr model of the atom has been improved over the past century, but it still provides a good basis for imagining how protons, neutrons and electrons in atoms are arranged
how big are atoms
an atom is 0.0000000001m in diameter
or 10^-10
what is a molecules
a molecule is a collection of atoms, strongly joined together or bonded.
how to work out the size of a molecules
a molecule with 100 atoms in a long line
the length of the molecules = 100atoms * 10^-10/atom
=10^-8m
