Atoms Flashcards
What did JJ Thompson do?
Discovered the electron and believed they were equally distributed throughout the atom.
What did Ernest Rutherford do?
In 1907, he discovered the nucleus and protons by firing alpha particles at gold foil. He deduced that atoms are mostly empty but contain a small, dense nucleus
What did Neils Bohr do?
He said that electrons orbit the nucleus in fixed layers called electron shells
What did James Chadwick do?
In 1932, he discovered neutrons, found that they weigh the same as protons and have no electrical charge.
What is an atomic number
Number of protons in an atom
What is a mass number?
Sum of protons and neutrons in an atom’s nucleus
What are isotopes?
Atoms of the same element with a different number of neutrons
Why are isotopes identical in their chemical reactions?
They have the same number of protons and electrons.
Characteristics of isotopes
Almost identical in chemical reactions.
Their physical properties are affected such as melting point and density.
What is a radioisotope?
An unstable form of a chemical element with unstable nuclei that releases radiation to become more stable
