Radioactive Decay
When does alpha decay occur? What is it's symbol?
when an unstable nucleus emits 2 protons and 2 neutrons
4/2 α OR 4/2 He
What is a carefully thought-out explanation for observations of the natural world?
a theory
Describe J.J. Thompson's discovery.
Used a cathode ray tube to show the smaller unit that makes up an atom
The ray produced in the cathode ray tube was deflected by an electric or magnetic field
the deflection of the light was due to negatively charged particles (electrons)
In Quantum Theory,
electrons exist in ____ that ______ the nucleus.
use _____ ______ as an approximation where the numbers are.
orbits, surround, quantum numbers
When does beta decay occur? What is its symbol?
when an unstable nucleus emits an electron
All matter is composed of four elements: earth, water, air, and fire
a grain of sand could be divided indefinitely
WHICH THEORY IS THIS?
Aristotle
Describe Ernest Rutherford's discovery.
Gold Foil Experiment directed alpha particles (positive charge) at a thin piece of gold foil
The deflected particles showed a dense, and positively charged center
concluded that atoms have a positively dense central core called a nucleus
What is the difference between a molecule and a compound?
A molecule is a group of 2+ atoms held together by chemical bonds, while a compound is a formed from 2+ different elements that are chemically combined in a fixed ratio.
atoms make up all material things
Atoms are unchangeable, indestructible and always existed
There are an infinite number of atoms in the universe
WHICH THEORY IS THIS?
Democritus
What 3 concepts were discovered in the Gold Foil Experiment?
1. protons
2. nucleus
3. everything outside the nucleus is empty
Describe cations vs. anions.
Cations
- electrons are lost
- positive ions
Anions:
- electrons are gained
- negative ions
All elements are composed of indivisible atoms
All atoms of a given element are identical
Atoms of different elements a have different masses
Compounds are formed by the combination of atoms of different elements
WHICH THEORY IS THIS?
John Dalton
In Bohr's model of the atom,
____ make up ____ shells around the nucleus.
shells ____ from the nucleus have a higher energy
electrons, 7, further
Electron Configuration describes ______.
the arrangement of electrons in an atom.
What 3 changes did we make to Dalton's theory?
an atom can be further subdivided
All atoms of an element are not identical in mass
We can create or destroy atoms
In the Planetary Model of the atom,
electron shells have a ____ energy and radius called a ____ state.
when electrons gain/lose energy and move to another shell its called an _____ state.
fixed, ground, excited