Unit 3&4 Test Flashcards
Strong Force
Keeps the nucleus together. Strong force has very limited range, therefore any nucleus to large will be unstable.
20 protons
1:1 is most stable
(21-81)
1:5:1
(82+)
Inherently unstable
Binding Energy+Mass Defect
The closer an atom is to iron (Fe 26) the more stable it is and energy will be released. The farther it is the more energy will be conserved.
A0
Amount of radioactive material that we start with
At
Amount of radioactive material remaining
Democritus
Theorized that everything is made of indivisible particles called atoms.
Joseph Proust
A given compound always contains the same ratio of elements.
John Dalton
(1) Elements consist of indivisible small particles (atoms). (2) All atoms of the same element are identical; different elements have different types of atom. (3) Atoms can neither be created nor destroyed.
J.J Thomson
Conducted the cathode ray tube experiment and concluded that there is something smaller than an atom because the cathode ray has a negative charge.
Plum Pudding Model
J.J Tomson’s model which theorizes that electrons are scattered across an atom and that the rest is positive matter, making the whole atom neutral.
Ernest Rutherford
Conducted the gold foil experiment in which he shot alpha particles at a thin piece of gold foil. Sometimes the particles would bounce back instead of going straight through the foil. Concluded that there must be a nucleus that has a positive charge and that atoms are mostly empty space.
Niles Bohr
Bohr proposed that electrons do not radiate energy as they orbit the nucleus, but exist in states of constant energy that he called stationary states. This means that the electrons orbit at fixed distances from the nucleus (see below). Bohr’s work was primarily based on the emission spectra of hydrogen.
Solar System Model
The “solar system” model represents an atom as a massive positive body which is the nucleus (like the sun in the solar system) with negative entities which are the electrons (like the planets in the solar system) orbiting around it.
Law of Definite Proportions
Joseph Proust (1800s, France)
A given compound always contains the same ratio of elements
E.g., water always has 2x as much hydrogen as it has oxygen.
Dalton-Law of Multiple Proportions
How does 12 g of carbon combine with oxygen?
12 g C combines fully with…
16 g oxygen
32 g oxygen
48 g oxygen
24 g oxygen
…but does not combine fully with 20 g oxygen
or other intermediate amounts
Critical Mass
A mass that is less than the critical amount is said to be subcritical (of insufficient size to sustain a chain reaction) while a mass greater than the critical amount is referred to as supercritical. Flat surfaces have greater critical mass which makes a chain reaction more difficult to sustain.
Mass Defect
Formula for mass defect is the difference of the mass of the protons and neutrons and the actual mass of the nucleus. The mass defect per nuclear particle is found by dividing the mass defect by the mass number (total p+n).
