P1.1 Flashcards
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What are things made of?
Greek philosopher Democritus first theorised the atom. The word ‘atomos’ meant indivisible in Greek, he said atoms were too small to see
What was Dalton’s model
in the 1870s John Dalton suggested that everything is made up of atoms. His model of an atom was a very small indestructible sphere. He said that all the atoms in an element are the same, and the atoms in one element are different from the atoms in all other elements
What was Thomson’s model
He found the particle called the electron that must have come from inside the atom and also worked out that the charge of the electron must be negative. Thomson said that an atom contains negative electrons and atoms have no overall charge, they are neutral. He suggested the atom is a positive sphere with negative electrons dotted around inside
Democritus and Dalton believed that all matter was made of tiny particles which they called atoms. Explain the difference between their theories?
Democritus said that atoms were too small to see and that atoms are the smallest thing ever and that there all atoms are the same. Dalton said that there were different atoms in different elements.
Compare Dalton’s model with Thompson’s model of the atom?
Dalton described the atom as the smallest thing, whilst Thomson said there were even smaller electrons within it
State the evidence that Thomson used to produce his plum-pudding model.
He used cathode rays
What is the Rutherford model?
A model of the atom with a positively charged nucleus with electrons around the outside. Most of the mass of the atom is the nucleus. When alpha particles hit the nucleus, they hit it and bounce back
What is the Bohr model?
Same as Bohr’s model except for the electrons that orbit on shells now
Describe the model of the atom that we use now?
Bohr’s atomic model with fixed orbits for electrons that orbit the nucleus
Describe evidence to show that the plum- pudding model is no longer an acceptable model of the atom?
The nucleus is the only bit that is positively charged, that is why most of the alpha particles went straight through the atom when fired. Only a small number hit the very small nucleus in the centre of the atom
Estimate the number of atoms in a molecule that is 2x10-10m long? Also explain why the number that you calculated is a maximum?
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