Chemistry History Flashcards
(7 cards)
how has the theory of atomic structure changed
5 points
1) John Dalton 19th century - atoms are solid spheres
2) JJ Thomson 1897 - plum pudding model
3) Ernest Rutherford 1909 - nuclear model
4) Niels Bohr 1900s - nuclear model
5) James Chadwick 1930s - neutrons
what was JJ Thomson’s ‘plum pudding model’ and draw it
3 points
1) the atom was a ball of positive charge
2) electrons randomly stuck in it
3) pg 31
what was Rutherford’s nuclear model and draw it
4 points
1) there’s a tiny positively charged nucleus at the centre of the atom where most mass is concentrated
2) a ‘cloud’ of negative electrons surrounds the nucleus
3) the atom is mostly empty space
4) pg 31
what was Bohr’s nuclear model and draw it
4 points
1) electrons orbit the nucleus in fixed shells
2) each shell is a fixed distance from the nucleus
3) pg 32
what did James Chadwick do
2 points
1) carried out an experiment that provided evidence for neutral particles in the nucleus
2) discovery of neutrons resulted in a model of the atom close to the modern day one
what was Rutherford’s alpha particle scattering experiment
4 points
1) fired positively charged alpha particles at a thin sheet of gold
2) from the PPM they were expecting particles to pass straight through the sheet
3) as the positive charge of each atom was thought to be very spread out
4) most particles did go straight through some were deflected back because of the nucleus
what was Mendeleev’s periodic table
4 points
1) put them mainly in order of atomic weight but switched the order of some according to their properties
2) gaps were left in the table to make sure elements with similar properties stayed in the same groups
3) some of the gaps indicated the existence of undiscovered elements
4) discovery of isotopes showed he was right no to place elements in strict order of mass as isotopes of the same element can have different masses but the same properties
