Chem Quiz 1 Flashcards
What did Democritus say in 300 B.C?
Atoms are indivisible, matter can be divided.
What did Dalton say in 1808?
- All matter is made up of tiny particles (atoms). 2. Atoms cannot be created,destroyed, or subdivided in chemical changes. 3. All the atoms of one element have the same properties (mass and size). 4. Atoms of different elements combine in specific proportions to form compounds.
Who created the model of the plum pudding and when?
JJ Thomson in 1904.
Describe the model of plum pudding.
The Plum Pudding Model is a model of atomic structure. Thomson had discovered that atoms are composite objects, made of pieces with positive and negative charge, and that the negatively charged electrons within the atom were very small compared to the entire atom. small negative particles in a positive sphere.
What did Rutherford do in 1911?
Performed the gold foil experiment and found out that both the nucleus and electrons are tiny. Most of the atom is empty space.
What did Rutherford do with the info gained from the gf experiment?
He created a new model of an atomic structure. With the electrons orbiting around the positive nucleus . Most of the atom is just empty place because most of the mass is in the tiny nucleus.
In standard atomic notation, what do the numbers around the element symbol mean?
Top left: mass# Bottom left: atomic #
What is an isotope?
Two or more atoms that have the same number of protons but not neutrons.
What do you call two atoms that have the same atomic number but a different mass number?
Isotopes
When you write an element like this: C-12 What does the 12 indicate?
The mass number.
What is the mass number?
The number of protons and neutrons.
What is the atomic number?
The number of protons.
What is a radioisotope?
An isotope that has an unstable nucleus.
What are the three principal uses of radioisotopes?
- Diagnosis and treatment of illnesses. 2. Dating fossils. 3. Smoke detectors.
What is the average atomic mass?
The weighted average mass of the isotopes of an element.
How are average atomic masses determined?
By using a mass spectrometer.
How do mass spectrometers work?
After ionization, acceleration, and selection of a single velocity, particles move into a mass spectrometer region where the radius of the path and the position on the detector is a function of the mass. They are passed through an electric field, then through a magnetic field.
What is the formula for average atomic mass?
a.a.m=(m1)(f1) + (m2)(f2) f= frequency (decimal) m= mass (in u)
What is the octet rule?
Atoms with a full outer shell (8 valence electrons) are very stable.
