Atomic Structure Flashcards
(33 cards)
Atomic structure History: Democritus
-around 500BC
-made atomic theory
What was the atomic theory?
-idea that everything is made up of tiny particles that can’t be broken down any further (atoms)
>particles separated by empty space
Atomic Structure History: John Dalton
-1803
-was the first to challenge Democritus’ atomic theory
What did John Dalton say about atoms?
-described atoms as solid sphere
-different types of spheres would make up different elements
Atomic Structure History: JJ Thompson
-1897
-came up with the plum pudding model
What change did JJ Thompson make to John Dalton’s theory?
-he said that the atoms couldn’t simply be solid spheres
-that they contained negatively charged particles (we now know as electrons)
What was the plum pudding model?
-theory that atoms are a ball of positive charge with electrons embedded in it
Atomic Structure History: Ernest Rutherford
-1909
-came up with nuclear model after conducting gold foil experiment
What was the nuclear model?
-theory that the atom had some sort of compact nucleus (that contained all of the positive charge)
-negative charge existed as some sort of cloud around the nucleus
What was the gold foil experiment?
> beam of +charged alpha particles passed through gold foil
-most went straight through the foil as expected (detected by a fluorescent screen)
ones shot towards the centre of gold foil went in unexpected angles, some even shot back in the same direction which they came from, meaning there was a compact centre of positive charge (nucleus)
-around nucleus, was mainly empty space with some electrons orbiting around it
Atomic Structure History: Niels Bohr
-1913
-fixed flaws to the rutherford model
What was Niels Bohr’s theory?
-that electrons orbited the nucleus in shells
-it was important as the orbiting of electrons stops them from being attracted to + nucleus and collapsing
Atomic Structure History: James Chadwick
-1932
-provided evidence that there are neutral particles in a nucleus (neutrons) after ernest rutherford discovered the protons
Neutron
-subatomic particle with neutral charge (0)
-relative mass is one
Proton
-subatomic particle with positive charge
(+1)
-relative mass is one
Electron
-subatomic particle with negative charge (-1)
-very small mass
Nucleus and shells of atom
-atom has central nucleus
>nucleus is surrounded by electrons orbiting it in shells
Atomic number
-found at the bottom of element on periodic table
-show the number of protons (or electrons) in an atom
All atoms of a given element have the same number of…
Atoms of different elements have…
….protons.
…different numbers of protons.
An atom contains equal numbers of protons and electrons. True or False
TRUE
What is an atom’s mass number?
-number of protons and neutrons found in the nucleus of an atom
-found at the top of the element
How do we find out the number of protons in an atom?
-look at its atomic number
How do we find out the number of electrons in an atom?
-look at its atomic number
How do we find put the number of neutrons in an atom?
-do
mass number - atomic number (number of protons)
