Atomic Theory definitions Flashcards

Terms Definitions
Positively charged?
Discovered Electrons
Plum Pudding model
A neutral particle
gold leaf experiment
who discovered the nuetron?
accidentally discovered radioactivity in 1896 while investigating fluorescent minerals
Moderen Day Atomic Structure.
negatively charged, 1/1800 amu
Cathode ray tube experiment
where r neutrons located
- luster
- malleable
- conductors
- react with acids
Created Law of Definite Proportions
means can not be divided
discovered an important numerical relationship that eventually contributed to our understanding of atomic electronic structure
Atoms exist, but no evidence
Had proof that atoms exist
Who made First Atomic Theory
Wave Model
Modern Day Atomic Model
energy levels with orbiting electrons
atoms exists but no evidence
John Dalton
atoms are tiny, solid, spheres
Atoms contain tiny particles with negative electrical charges-scientist
made law of conservation of mass
2 or more elements chemically combined
Crookes Tube / Cathode Ray
J.J. Thomson
Who made Law of Definite Proportions
qualitative studies of cathode rays- Electricity is composed of negatively charged particles.
helps make the Thomson Theory.
J.J Thompson
-discovered ELECTRON
-made PLUM PUDING model
-CATHODE RAY experiment
whose atomic theory remained the accepted truth for 2000 years
theory of matter that competed with Democritus; thought all matter consisted of 4 primary elements: earth, fire, water, air; believed matter could be infinitely divided; 4th century BCE
physical properties of metals
shininess, malleability, ductility, conductivity
the shapes of the orbits of electrons
Earnest Rutherford
Discovered protons through the gold foil experiment
first said that elements have atoms
John Dalton
Chemical property
a characteristic of a substance observed in chemical reactions, which changes the identity of the substance(s)
atoms of an element that are chemically alike but different in mass
beta rays
(negative in charge) similar to Thomson's electron,but higher in energy
far apart, high energy, move quickly in random order, indefinite shapeand volume
Niels Bohr
suggested that electrons travel around the nucleus in definite paths
Developed the Electron dot model to show valence electron structure [valence electrons are the electrons which actualy take part in the chemical change
consists of two more substances that can be separated.
heavy radionuclide splits into 2 or more intermediate-sized fragments when struck by a neutron
1. atom splits to produce fission products, energy, and more neutrons
2. reaction in which products cause additional reactions is called chain reaction
3. For chain reaction, enough fissionable material must be present to cause at least one more fission; this is the critical mass
4. Process used to generate electrical power and in early atomic bombs
beta radiation
a piece of paper will provide protection from
James Chadwick
- Discovered Neutron
-Atom is an empty sphere with nucleus
-Nucleus contains protons and neutrons
- Electorns orbit nucleus
-Neutral Atom = same # of protons and electrons
what is an electron?
particle with a negative charge.
atoms of the same element have the same number of
atoms of the same element have the same # of protons but not the # of neutrons
Atomic Theory
atoms are the building blocks of matter and that different types of atoms exist for different types of matter
atomic mass
since the number of neutrons is different in an isotope, the _____ _______ is different
subatomic particle
particles that are smaller than an atom
a substance that is made from the atoms of 2 or more elements
Two elements that the Curie's discovered
Radium and polonium
1. composed of 2 protons and 2 neutrons or Helium nucleus
2. mass of about 4 amu
3. 2+ charge
4. Symbolically: a or ⁴₂He
5. when an element loses an a particle it becomes a new element
6. E.g.,
²⁸³₉₂U > ²³⁴₉₀Th + ⁴₂₂He
or natural uranium becomes thorium after losing a particle
Antoine Lavoisier
First to state that mass cannot be created or destroyed
Cathode Ray Experiment
a positively charged plate attracted a beam of electrical energy; Thomson discovered negatively charged particles in every kind of atom called electrons
Law of Multiple Proportions
when different compounds are formed from the same elements, the elements are in small whole number ratios
compounds are formed when atoms of two or more different elements are combined
3-compounds are...
atomic number
the number of protons in an atom's nucleus
the number of waves or cycles per unit of time
J.J. Thompson
made a discovery that there are small particles inside the atom. Came up with the "plum pudding" model
polar molecule;
has a negative or positive areas, will form hydrogen bonds with water or other molecules
Rutherford Discovered
Nucleus and the 3 main components of radiation , nucleus mostly have a positive particle (nucleus and proton)
Periodic Trends
1. Group 1A: +1 ion only; e.g., Na+
2. Group 2A: +2 ion only; e.g., Ca2+
3. Group 3A: Al+3 and Ga+3
4. Group 6A: usually -2; e.g., O-2
5. Group 7A: usually -1; e.g., Cl-
6. Group 8A: not ionic
7. Group B metals: vary except for Ag+ and Zn2+ which have only 1 valence
everything was made up of Earth, air, fire and water
greeks found that
law of conservation of mass
Matter is neither creater nor destroyed
half life
the time needed for one half of a radioactive sample to decay and become non-radioactive
wave mechanical model
modern model of the atom, shows the most probable location for an electron-called the orbital, and electrons have wave-like properties.
Nobel Gases
Elemenets that do not like to bond or react. Very stable
Period #
=n, the principal quantum # OR # of electron shell
Modern Atomic Theory #2
All atoms of the same element are exactly the same.
Rutherford's Model
found that the most of the mass in an atom was in the center of the atom; discovered the nucleus- a place where most of the positive charges and atoms are located
Schrodinger Wave Equation/Schrodingers model of the atom
Honey Pot and Bee Analogy! Found where greatest concentation of electrons were w/ different number of electrons in an atom. Found that w/ 1 electron, 95% were found in an imaginary sphere. "Best fit sphere"
Atomic Mass Unit (AMU)
The SI unit that describes the mass of an atom or its particles
What does Democritus believe about the atom?
It cannot be further divided, All things are made from atoms, which are small, invisible, and indestructible particles of pure matter, and atoms are in constant motion. He believed in the billiard ball.
probability in qmm
ratio b/ the # of times the e- is in that certain position and the total number of times it is at all possible positions
What are the three different types of radiation and describe them.
Alpha: much more massive than the beta particles and have a positive charge; Beta: have a negative charge and are like high energy electrons; Gamma: no charge, and the most damaging of the three.
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