atomic structure Flashcards
At the start of the 19th century what did people believe and who made this theory ?
- John Dalton
- described atoms as solid indivisible spheres
state the plum pudding model ?
an atom was a ball of positive charge with negative electrons scattered within it.
who founded the plum pudding model and what else did he find ?
- J.J Thompson
- discovered electrons which showed that atoms were not solid and idivisible
state the nuclear model ?
atoms have a tiny positively charged nucleus which is surrounded by a cloud of negative electrons
- most of the atom is empty space
what was the experiment called and who carried it that led to the creation of the nuclear model ?
- Ernest Rutherford
- gold leaf/foil experiment
who proposed the Bohr model and describe the Bohr model ?
_ Niels Bohr
- scientists realised that electrons in a cloud around the nucleus would quickly spiral down into the nucleus and cause it to collapse.
Bohr stated that electrons orbit the positively charged nucleus in fixed energy levels
and when electrons move between shells, electromagnetic radiation is emmitted or absorbed
What did the Bohr model fit ?
it fitted experimental observations of the radiation emmitted and absorbed by atoms
What did scientists later discover after the Bohr model ?
they discovered that not all the electrons in a shell have the same energy so they refined it to include sub-shells
In the bohr model what particles are in the nucleus and how are they held together ?
- protons and neutrons
- held together by strong nuclear forces
what force holds the electrons in place around the nucleus ?
electrostatic forces of attraction
which force ( nuclear or electrostatic) is stronger ?
nuclear is much stronger
what is the mass number ?
the number of protons and neutrons in the nucleus
what is the atomic number ?
the number of protons in the nucleus of an atom
what is meant by an isotope ?
are atoms of the same element that have the same number of protons but a different number of neutrons
what is the reactivity
/ chemical properties of an element determined by ?
the number and arrangement of electrons decides the elements chemical properties
