Atomic Structure and Model Flashcards
what did John Dalten say about atoms
- all matter is made of atoms
- atoms are indestrucible and cant be broken down
- atoms of an element are identical
- atoms are rearranged in a chemical reaction
- compunds = 2 or more different atoms chemically joining together
how are atoms in different elements different
number of protons, neutrons and electrons
why do atoms have an overall charge or charge of 0
because they have the same number of protons and electrons
what ratio is the size of the nucleus to the atom
1 to 10,000
what is the atomic number of an atom
number of protons which indicates number of electrons
what is the mass number of an atom
protons and neutrons added up
what is an isotope
element with same number of protons but different number of neutrons and mass number
what is relative atomc mass
weighted average of the masses of an atom of the isotopes for an element
how to work out relative atomic mass (Ar)
Ar = (mass1 X percentage1) + (mass2 x percentage2) / 100
who was the second person to develop ideas about the atom and what did he say (with what model)
- JJ thompson
- discovered electrons and said that atoms are built up of smaller pieces
- plum pudding model suggested that for atoms to be neutral and have a positive charge (the pudding) they must have negatively charged particles
who was the third person to develop ideas about the atom and what did he say
- Rutherford
- showed that atoms have a nucleus that included positive particles
- this was done with alpha particle scattering. the atom was a nuclear atom
what is alpha particle scattering
experiment by rutherford that consisted of shooting alpha particle radiation at a sheet of gold and observing for any reactions between an opposite force
how do deflection of alpha particles suggest a nucleus exists
some alpha particles bounced back and most changed direction, meaning a large opposing forces must have acted on them, so theres a concentrated positive charge in the atom deflecting them back
what did the small deflections of the alpha particle suggest about the atom
suggests that it consists of alot of empty space, so there must be a nucleus
who was the fourth person to develop ideas about he atom and what did he say
bohr further developed rutherfords nuclear atom model and proved that electrons are organised in shells surrounding the nucleus
what does the development of the theory of the atomic structure show
how a theory may change if new evidence is found
relative mass of an electron
0.0005
how do isotopes impact the relative atomic mass of an element
if there is a lot of an isotope it will impact the average mass and therefore the elements atomic number
what did the alpha particle scattering disprove and how
- the plum pudding model
- model suggests that the atom is mainly positive and its charged is spread out
- but the positive particles bouncing back means theres a concentrated positive charge
what did rutherford describe the atom to look like
a tiny positive charge at the center where most of the mass is concentrated with a cloud of electrons surrounding the nucleus
