Atomic Structure Flashcards
He was a Greek philosopher over 2000 yrs. ago. Believed there was a limit to dividing matter. Eventually you would reach the smallest piece and could no longer divide it without losing its identity. Democritus named the smallest piece of matter the atom. The word atom comes from the Greek word atomos meaning “un-cuttable”(a-tom).
Used only observations
Different atoms for every substance.
* He believed the world consisted of only two things: Atoms and the empty space around them.
* He was not believed because there was no proof and Aristotle did not believe in this.
Democritus (400 B.C.)
Used only observations
Different atoms for every substance.
* He believed the world consisted of only two things: Atoms and the empty space around them.
* He was not believed because there was no proof and Aristotle did not believe in this.
Democritus
Father of the modern atomic theory!
John Dalton (1800’s)
Dalton’s Atomic Theory
All elements are composed of atoms. Atoms are indivisible and indestructible particles
Atoms of the same element are exactly alike
Atoms of different elements are different
Compounds are formed by the joining of atoms of two or more elements.
He also proposed the first symbols for elements.
Cathode Ray Experiment Discovered Electrons (negative charge) Model was like a plum pudding. According to Thomson, the atom was made of a pudding-like positively charged material throughout which negatively charged electrons were scattered,like plums in pudding. Thus, “plum pudding model”.
J.J. Thomson (1900)
This great magician was born at the beginning of the fifth century BC, he first suggested that the world around us was made of elements - admittedly he only had four elements and spent the rest of his time as a magician.
- Earth, air, fire, and water
Empedocles of Acragas(490 - 430 BC)
Gold foil experiment
Discovered the nucleus (positive charge)
Model was like a solar system.
Also discovered alpha particles: positively charged particles emitted from certain radioactive substances.
Ernest Rutherford (1911)
Energy Level Model
The farther the energy level is from the nucleus, the greater the energy of the electron.
Adding energy moves an electron farther away from the nucleus. (Outer energy levels)
Energy is given off as an electron moves in.
Bohr (1913)
Wave Model
Very Complex
Electrons can be found anywhere in a certain region around the nucleus.
Model like the blades of a fan. (electrons are in all places at the same time)
DeBroglie
Uncertainty Principle.
Nothing can be observed in its natural shape because observing changes the very nature of things being observed.
You can not know the location and the velocity of an electron at the same time.
Heisenberg
Quantum Reality
Matter exists in all states except when being observed.
Can you travel across quantum realities?
Which one matters?
Schrodinger
Discovered neutrons
Scientist could not account for the density and mass of the nucleus on just the mass of a proton alone; in 1932, Sir James Chadwick did experiment similar to Rutherford’s and discovered the existence of neutrons.
Chadwick
Mass of a proton
approximately 1 amu
Mass of a neutron
approximately 1 amu
Charge of a proton
+1
Charge of a Neutron
0
Charge of an electron
-1
Mass of an electron
1/1836 amu
Considered to be negligible
If a water molecule were the size of a golf ball, a glass of water would be as big as
the Earth.
If a hydrogen nucleus was as big as a tennis ball, the electrons could be as far away as
.(from Cedar Shoals HS)
UGA
Is the same as the number of protons.
If you add or subtract protons, it is a NEW element.
In a neutral atom, # of protons = # of electrons.
Atomic Number
This = # of protons + # of neutrons. # of neutrons = This - # of protons
Mass Number
of neutrons = This - Atomic #
Mass Number
All atoms have neutrons except for
Hydrogen-1(protium).
Does the number of neutrons always equal the number of protons?
no
Atoms of the same element with different numbers of neutrons.
Atoms have the same atomic number but a different mass number.
These are indicated by writing the name of the element followed by a number; ex: Sodium-23 (has 11 protons and 12 neutrons.)
The mass of an atom in relation to carbon-12 is called the atomic mass.
Final atomic mass depends on these.
Isotopes
Exact location is somewhere in electron cloud.
Electrons
Exact location is somewhere in electron cloud.
Found at different energy levels
Electrons
Level 1: __ electrons
Level 2: __ electrons
Level 3: __ electrons
Level 4: __ electrons
2
8
18
32
Electrons that move from one level to another either_____ or _____ energy.
gain or lose
The abundance of a chemical element measures
how relatively common the element is, or how much of the element there is by comparison to all other elements.
number of protons
*Always a whole number.
Atomic Number
