Atoms Exam 2024
atom - answer are so small that we can't see them, scientists must rely on indirect
evidence to make models of atoms
- a model is an attempt to use familiar ideas to describe unfamiliar things in a visual way
Democritus - answer “atom" comes from the word the Greek word "Atomos" which
means indivisible
- idea that all matter is made up of atoms was first proposed by Greek philosopher
Democritus in the 5th century
John Dalton (1766 - 1844) - answer performed experiments that showed that matter did
consist of some kind of basic lumpy particles
- elements are made out of particles that are all alike
Joseph John Thompson (JJ) - answer performed experiments with the cathode ray tube
and discovered that atoms could sometimes eject a far smaller negative particle which
he called an *electron*
- plum pudding model
- discovered electrons
Ernest Rutherford (1871 - 1937) - answer1909 performed gold foil experiment and
suggested the following characteristics of the atom
- consists of a nucleus that contains most of the mass of the atom
- nucleus is made up of protons (positive) and neutrons (neutral)
- electrons are negatively charged, but most of the atom is empty space
- Rutherford's atom
Niels Bohr (1885 - 1962) - answer Bohr model - electrons travel around the nucleus of
an atom in orbits on a definite path
- the electrons can jump from a path in one level to a path in another level(depending on
their energy)
-electrons with more energy are located farther away from the nucleus
James Chadwick (1891 - 1974) - answer realized that the atomic mass of most
elements was double the number of protons - discovered the neutron in 1932
the present atomic model - answer- electrons are likely to be found moving in certain
regions around the nucleus of an atom
-these regions are called electron clouds
-each electron cloud has a definite energy level
isotopes - answer atoms of the same element can have a different number of neutrons
atom - answer are so small that we can't see them, scientists must rely on indirect
evidence to make models of atoms
- a model is an attempt to use familiar ideas to describe unfamiliar things in a visual way
Democritus - answer “atom" comes from the word the Greek word "Atomos" which
means indivisible
- idea that all matter is made up of atoms was first proposed by Greek philosopher
Democritus in the 5th century
John Dalton (1766 - 1844) - answer performed experiments that showed that matter did
consist of some kind of basic lumpy particles
- elements are made out of particles that are all alike
Joseph John Thompson (JJ) - answer performed experiments with the cathode ray tube
and discovered that atoms could sometimes eject a far smaller negative particle which
he called an *electron*
- plum pudding model
- discovered electrons
Ernest Rutherford (1871 - 1937) - answer1909 performed gold foil experiment and
suggested the following characteristics of the atom
- consists of a nucleus that contains most of the mass of the atom
- nucleus is made up of protons (positive) and neutrons (neutral)
- electrons are negatively charged, but most of the atom is empty space
- Rutherford's atom
Niels Bohr (1885 - 1962) - answer Bohr model - electrons travel around the nucleus of
an atom in orbits on a definite path
- the electrons can jump from a path in one level to a path in another level(depending on
their energy)
-electrons with more energy are located farther away from the nucleus
James Chadwick (1891 - 1974) - answer realized that the atomic mass of most
elements was double the number of protons - discovered the neutron in 1932
the present atomic model - answer- electrons are likely to be found moving in certain
regions around the nucleus of an atom
-these regions are called electron clouds
-each electron cloud has a definite energy level
isotopes - answer atoms of the same element can have a different number of neutrons
