Chapter 2 Flashcards
(27 cards)
Who began the term atoms?
2,000 years ago, Democritus and Leucippus said that all matter is made up of atoms, small indestructable particles!! Individible, cant be divided
Daltons Atomic Theory?
-All elements composed of atoms
-All atoms of the same element are exactly alike
-atoms of different elements are different
The atoms that make a compound are definite proportions.
Law of Definite Composition:
a compound always contains 2 or more elements combined in a definite ratio. ex: h2o
Law of Multiple Proportions:
Atoms of two or more elements may combine in different ratios to produce more than one comd.
eX: h2o=water
h202= hydrogen peroxide
JJ Thompsons “Plum Pudding Model What year
1897- there are things inside the atom smaller than the atom and are charged!
Gold Foil Experiment? Who did it? and what year
Rutherford’s Gold foil experiment in 1911
What was Rutherfords Gold foil experiment?
He found that most of the alpha particles went straight through the gold foil, and when he examined the gold foil there was no holes in the gold foil, it remained completely solid, The matter went through matter and went out through the other side!
used a radio active alpha particle
What was his main and secondary conclusion?
An atom is made up of mostly emoty space, since the alpha particles went through
Most of the mass and (+) charge is located in a small, dense, centrally located nucleus
Diameter of Nucleus
Diameter od Atom
10 to the -15m
10 to the -10m
Niels Bohr discovery in what year
1913- discovered that the negative particles exist in orbits (principle energy levels) outside the nucleus
James Chadwick in what year discovered what?
1932- Discovered the Nuetron- a nuetral particle which exits in the nucleus and buffers the protons from repelling eachother
What does atomic number mean in an atom on the periodiv table?
the protons from nuetrons
Proton
Nuetron
Electron
Symbol Mass and Charge
Proton= p+, 1 amu, +1 Nuetron= nO, 1amu, no charge
electron, e-, 1/1836 amu, -1
1 amu=
1/12 the mass of a carbon-12 atom
Where do protons and nuetrons live?
in the nucleus of the atom and electrons orbit around it
What is the standard format for representing an element with the atomic mass and atomic number?
The atomic mass goes on top and the atomic number goes on the bottom,
ex: Carbon atom the 12 is on top and the 6 is on bottom
What does the atomic number give?
The amount of protons
What does the atomic mass give
Protons + neutrons
Principal energy level and how many electrons can fit ?
1=2
2= 8
3=18
4=32
why arent the atomic mass of elements whole numbers?
bc the atomic mass is a weighted average of the isotopes
what are isotopes?
Atoms of the same element that contain the same proton and electrons but different neutrons= different masses
Group 1 A
Alkali metals, shiny soft
shiny soft low melting point
Group 2a
Alkaline metals
group 7a
Halogens
