CHEMISTRY EXAM REVIEW
UNIT 1 A
Terms
Chemistry - The study of matter, its nature and the changes it undergoes
Matter - anything that has mass and takes up space
Mass - How much matter something has
Weight - Earth's gravitational effects on mass
History of the Atom
1. Democritus - Produced the fundamental building blocks for the idea of the atom. He
thought that if you keep dividing a piece of something, you would eventually reach a
piece that you can't divide anymore, he called that piece “atomos” meaning “indivisible”
2. John Dalton - Proposed that atoms are tiny indestructible spheres, his theory was:
a. All matter is made up of tiny particles called atoms
b. All atoms of the same element are identical
c. All atoms of different elements are different from each other
d. Atoms combine to form simple ratios called compounds
e. When atoms react, they don’t just disappear, they either:
i. Join together
ii. Rearrange
iii. Separate
3. Sir William Crokes - Did experiments with crookes tubes, involving cathode rays, he
conducted four main experiments and concluded four things:
a. He shone cathode rays onto various elements, regardless of the element, they all
glowed. His conclusion was that cathodes are common to every element
b. He inserted a small cross in the flow of the cathodes; when finished, the rays left
a burnt mark all around the cross. His conclusion was that cathode rays travel in
straight lines
c. He inserted paddle wheels in the flow of the cathode rays, when rays were
flowing, they turned the wheel. His conclusion was that cathode rays have mass
because they exert force on the wheel to spin it
d. Next he put magnets next to the flow of the cathodes, the cathodes were
deflected. His conclusion was that cathode rays are negatively charged since
they come from a negative electrode
4. J.J Thompson - Proposed the idea of the raisin bun model, where the atom was a
sphere and had its charges evenly spread out within it. He showed that the electron had
a much lower mass than even the lightest atom
5. Sir Ernest Rutherford - Conducted a gold foil experiment where he tested J.J
Thompson's model of the atom. He took gold and made it into a very thin sheet, then he
, CHEMISTRY EXAM REVIEW
put a screen all around this experiment. He was expecting that when alpha particles
were in contact with the atoms, they would move through the atom and get slightly
deflected. However he witnessed that:
a. Most particles passed right through the atom, meaning they are mostly empty
b. Any particles that came if contact with the nucleus got deflected, meaning there
was a small dense core
c. Some particles got hit bang-on and got deflected right back, meaning the nucleus
had to be positive in order to repel the alpha particles
Faults of the Gold Foil Experiment:
a. Vague about position and motion of electrons
b. Didn't explain what holds atoms of molecules together
6. Nelis Bohr - Came up with the planetary model of the atom, where electrons acted as
planets and the sun acted as the nucleus. Proposed six main ideas:
a. Electrons travel around the nucleus
b. Each orbit holds a maximum number of electrons
c. Each orbit has an energy level
d. When exited, atoms from lower valences can jump from their ground state to
exited states, and when falling back to their ground states, they release energy in
the form of visible light - (2) ideas here
e. Electrons are found in orbits, not in between
Atomic Notation
Easy way to express information about an atom. Nelis Bohr made this
Bohr Diagrams
Frederick Soddy - Proposed the existence of isotopes (atoms that have additional neutrons)
James Chadwick - Proved the idea of the neutron (important because they keep nucleus
together, preventing positive charges from repulsion)
UNIT 1 A
Terms
Chemistry - The study of matter, its nature and the changes it undergoes
Matter - anything that has mass and takes up space
Mass - How much matter something has
Weight - Earth's gravitational effects on mass
History of the Atom
1. Democritus - Produced the fundamental building blocks for the idea of the atom. He
thought that if you keep dividing a piece of something, you would eventually reach a
piece that you can't divide anymore, he called that piece “atomos” meaning “indivisible”
2. John Dalton - Proposed that atoms are tiny indestructible spheres, his theory was:
a. All matter is made up of tiny particles called atoms
b. All atoms of the same element are identical
c. All atoms of different elements are different from each other
d. Atoms combine to form simple ratios called compounds
e. When atoms react, they don’t just disappear, they either:
i. Join together
ii. Rearrange
iii. Separate
3. Sir William Crokes - Did experiments with crookes tubes, involving cathode rays, he
conducted four main experiments and concluded four things:
a. He shone cathode rays onto various elements, regardless of the element, they all
glowed. His conclusion was that cathodes are common to every element
b. He inserted a small cross in the flow of the cathodes; when finished, the rays left
a burnt mark all around the cross. His conclusion was that cathode rays travel in
straight lines
c. He inserted paddle wheels in the flow of the cathode rays, when rays were
flowing, they turned the wheel. His conclusion was that cathode rays have mass
because they exert force on the wheel to spin it
d. Next he put magnets next to the flow of the cathodes, the cathodes were
deflected. His conclusion was that cathode rays are negatively charged since
they come from a negative electrode
4. J.J Thompson - Proposed the idea of the raisin bun model, where the atom was a
sphere and had its charges evenly spread out within it. He showed that the electron had
a much lower mass than even the lightest atom
5. Sir Ernest Rutherford - Conducted a gold foil experiment where he tested J.J
Thompson's model of the atom. He took gold and made it into a very thin sheet, then he
, CHEMISTRY EXAM REVIEW
put a screen all around this experiment. He was expecting that when alpha particles
were in contact with the atoms, they would move through the atom and get slightly
deflected. However he witnessed that:
a. Most particles passed right through the atom, meaning they are mostly empty
b. Any particles that came if contact with the nucleus got deflected, meaning there
was a small dense core
c. Some particles got hit bang-on and got deflected right back, meaning the nucleus
had to be positive in order to repel the alpha particles
Faults of the Gold Foil Experiment:
a. Vague about position and motion of electrons
b. Didn't explain what holds atoms of molecules together
6. Nelis Bohr - Came up with the planetary model of the atom, where electrons acted as
planets and the sun acted as the nucleus. Proposed six main ideas:
a. Electrons travel around the nucleus
b. Each orbit holds a maximum number of electrons
c. Each orbit has an energy level
d. When exited, atoms from lower valences can jump from their ground state to
exited states, and when falling back to their ground states, they release energy in
the form of visible light - (2) ideas here
e. Electrons are found in orbits, not in between
Atomic Notation
Easy way to express information about an atom. Nelis Bohr made this
Bohr Diagrams
Frederick Soddy - Proposed the existence of isotopes (atoms that have additional neutrons)
James Chadwick - Proved the idea of the neutron (important because they keep nucleus
together, preventing positive charges from repulsion)
