Unit 2 Test Flashcards
What was the 1st idea of the atom?
The 1st idea of atom was from the Greek philosopher, Democritus. He believed that matter was composed of tiny indivisible particles called atoms. Since it was so long ago, and they had very little technology, he had no experimental evidence to support his thoughts.
State 4 major ideas of Dalton’s Atomic Theory:
1) All elements are composed of invisible particles called atoms
2) Atoms of the same element are identical. The atoms of any one element are diff. from those of another
3) Atoms of diff. elements mix or combine in whole number ratios
4) Chemical reactions occur when atoms separate, join, or rearrange. In a chemical reaction, atoms of another element NEVER change into another.
What is the experiment that led to the discovery of the electron?
The Cathode Ray Tube Experiment led to the discovery of an atom. There was a tube with insert gas and 2 plates, a positive and negative one. The particles in the gas were attracted to the positive plate, and therefore we conclude that the particles must have a negative charge (opposites attract)
Explain Rutherford’s gold foil experiment.
Rutherford shot a high beam of positive alpha particles into a sheet of gold foil. Some of the particles were scattered/deflected which led to the conclusion that the atom has a tiny, hard and dense crystal re at the center of the atom, called the nucleus.
What are the 3 subatomic particles and what are their charges?
Protons: positive charge
Neutrons: neutral
Electrons: negative charge
What does the atomic number represent?
The number of protons in the element
What does the mass numbers represent?
The number of protons and neutrons combined
What are isotopes? How are they the same? How are they different?
Isotopes are atoms with the same number of protons, but different number of neutrons. They are the same because they are all chemically alike, but the are different because they have different mass numbers.
What does the atomic mass represent?
The average (weighted) of all the element’s isotopes
What is an ion?
At Tom’s or group that has positive and negative charge.
What are the 2 ways in which you can form an ion?
1) When an atom gain electrons
2) When an atom loses electrons
What is density? What is the formula?
Density is the amount of mass per unit volume.
Formula: D= m/v
Calculate the atomic mass of Carbon if the two common isotopes of Carbon have masses of 12 amu (98% abundance) and 13.003 Amy (1.11% abundance)
12.011 = atomic mass of Carbon
Calculate the atomic mass of sulfur if the four common isotopes of sulfur have masses
of 31.972 amu (95.00 % abundance), 32.971 amu (0.76%), 33.967 amu (4.22 %), and 35.967 amu (0.014 %).
32.05 = atomic mass of sulfur
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