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Exam 1 Chem 1055
Terms in this set (37)
What did Democritus do?
introduced the idea of an atom
Who came up with the Law of Conservation?
What is the first principle of Dalton's Atomic Theory?
All matter is made up of small, indestructible particles called atoms
What is the second principle of Dalton's Atomic Theory?
In an element, all atoms are identical
What is the third principle of Dalton's Atomic Theory?
Compounds are made up of a combination of atoms
What is the fourth principle of Dalton's Atomic Theory?
Chemical reactions involve rearrangement of atoms
What did JJ Thomson discover?
What did Thomson use for his experiment?
Cathode Ray Tube
Explain Thomson's experiment
Used Cathode Ray Tube - put electrically charged metal on either side - shot cathode rays out - they deflected away from the negatively charged plate, showing that there were negatively charged, subatomic particles
How did Thomson's discovery compare to principles in Dalton's Atomic Theory?
It disproved his first principle that "All matter is made of small, indestructible particles called atoms" because it showed that there were negatively charged, subatomic particles
What Model did Thomson provide?
Plum Pudding Model
Explain Thomson's Model of an atom
There is a soupy inside of an atom that was full of positively charged particles with negatively charged electrons studded around it
What did Ernest Rutherford discover?
The nucleus is dense, positively charged, and only makes up a small part of the atom (aka an atom is mostly empty space)
Explain Rutherford's Experiment
Gold-Foil/Geiger-Marston experiment had positive alpha rays emitted towards different pieces of metal - it reacted with gold, so they continued the rest of their experiment shooting the rays at the gold - if Thomson's model was correct, all the positive particles would shoot right through with little deflection - what actually happened was the full deflection of a few particles
What was the conclusion of Rutherford's experiment
Showed that there were some dense portions of am atom that were positively charged and localized enough to completely deflect alpha rays (aka the nucleus was positive and dense) - It also showed that much of an atom was empty because of the ability of the other alpha particles to continue to to right through
What model did Rutherford create?
Explain Rutherford's Model
There is a small, dense, positively charged core surrounded by electrons that orbit the atom
What is James Chadwick known for?
Identifying neutrons in the nucleus
What is a theory and how does it differ from a law?
A theory is an explanation for natural phenomena backed by experimental data covering a broad range of predictions. A law, on the other hand, has no explanation, but is empirical and has mathematical description
Anything that has mass and takes up space
What is the structure of an atom?
heavy, dense nucleus made of protons and neutrons which is orbited by light, negatively charged electrons
What is the difference in an element and a molecule?
An element is made up off all of the same atoms, whereas as molecule is composed of 2 or more atoms (bound by covalent bonds)
What is a compound?
a combination of two or more elements
Compare observation and experiment
An observation is the simple action of passively watching and taking notes of results. An experiment is directly and actively manipulating variables to test a prediction and see the outcome
Piece, Charge, and Place: Neutron
Neutral, Nucleus, relative mass of 1
Piece, Charge, and Place: Electron
Negative, outside of nucleus, relative mass of 0
Piece, Charge, and Place: Proton
Positive, nucleus, relative mass of 1
same atom with different number of neutrons
What can be said of the chemical properties of an isotope
They tend to be the same (if one reacts to something, there is a very high chance that another will also react in the same manner)
Explain the physical properties of isotopes
They tend to differ (ex: density, magnetism, and radioactivity)
What is an ion?
an atom with uneven numbers of protons and electrons
What are the two types of ions and what do they mean?
Cation = lost electrons (positive charge)
Anion = gained electrons (negative charge)
What is an atomic number?
the number of protons in an atom
Where is the atomic number found?
on top of the letter on the periodic table
What is the symbol for atomic number?
Where is the atomic mass found?
below the letter
What is the symbol for atomic mass
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