The Periodic Table Flashcards
400 B.C Democritus
Democritus, a Greek philosopher, proposed that matter was made up of small, hard, invisible particles, which he called atoms after Atomos(cannot be cut)
1800 Dalton
Dalton visualised atoms as tiny solid balls. His main conclusions were:
All matter is made of indestructible atoms
All atoms of a particular element are identical to each other
1897 JJ Thompson
Thomson discovered that atoms were not solid spheres but contained smaller, negatively charged particles which he called electrons.
Since the atom as a whole had to be neutral, he imagined the electrons to be embedded in a sphere of positive charge.
1909 Rutheford
The positive particles from radium were allowed to fall on a thin piece of gold foil. If the model was right, the particles should be repelled by positive charge of the atom and deflected through a range of angles. The only explanation was that the “plum pudding” model was wrong and the atom was mostly empty space with the positive charge concentrated in a very small nucleus at the centre of the atom.
1911 Bohr
Bohr proposed a model for the atom in which the electrons are in fixed energy levels or shells. He was able to produce a mathematical model for the hydrogen atom.
1932 Chadwick
The discovery of the neutron by Chadwick in 1932 finally allowed chemists to make sense of the periodic table with atoms composed of neutrons, protons and electrons.
How many electrons are in the outer shell of group 1 elements?
They all have 1 electron on the outer shell
when going down group 1, what happens to the size of the atoms and what effect does this have on the reactivity?
The electron in the outer shell gets farther away from the nucleus. This means that the electron is easier to remove and so the metals become more reactive.
How do these metals form compounds with other elements?
They all form compounds by ionic bonding. i.e. They lose the single electron to form a positive ion leaving a full outer shell.
