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Chemistry Chapter 3 10.15.05


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The smallest particle of an element that retains the chemical properties of that element
Electron Cloud
Region that is occupied by electrons
Are P+ and are positive
Nuclear Forces
Short range proton-neutron, proton-proton, nuetron forces hold the nuclear particle together
Are E- and are negative
Are N and neutral
Revealed that the electron has a negative charge using the plum pudding experiment
Led in the gold foil experiment
Determined that electrons have a negative charge using the oil drop experiment
Had the earliest particle theory of matter in 400 bc. He called it a atom and said it was indivisible
Created the atomic theory in 1808 where he came up with five ideas on atoms
Law of Conservation of Mass
Mass is neither destroyed nor created during ordinary chemical reactions or physical changes
Law of Multiple Proportions
If two or more different compounds are composed of the same two elements, then the ratio of the masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers
Law of Definite Proportions
The fact that a chemical compound contains the same elements in exactly the same proportions by mass regardless of the size of the sample or source of the compound
Atoms of the same element that have different masses
Average Atomic Mass
The weighted average of the atomic masses of the naturally occurring istopes of an element
General term for any isotope of any element
Atomic Mass Unit
Unit of mass that is exactly 1/12 the mass of a carbon-12 atom or 1.660
Avogadros Number
Number of particles in exactly one mole of a pure substance

6.02 x 10 23
Amount of a substance that contains as many particles as there are atoms in exactly 12g of carbon-12
Describe the gold foil experiment of Rutherford, Geiger and Marden. When did this happen?
(1911) Bombarded a thin piece of gold foil with a narrow beam of alpha particles. Some of the particles were redirected by the gold foil back toward their source
What was Rutherford's explanation. When did this happen?
(1913) There is a small densely packed, postive nucleus. Electrons travel in a circular orbit around the nucleus
What's in the nucleus and what are their charges
Protons - Positive

Nuetrons - Nuetral
Atomic Number (symbol)
(Z) Is the number of protons in the nucleus of each atom of that element
What element has the most stable isotope? How many does it have

10 isotopes
What are two ways you identify isotopes by
1. The mass number is written with a hyphen after the name of the element

2. Show the composition of nucleaus
Which particles determine the element
What are the three mass numbers of the 3 isotopes of hydrogen
1, 2 and 3
Mass Numbers (symbol)
(A) Total number of protons and neutrons in the nucleus of an isotope
How do the masses of the atomic particles compare
Neutrons are slighty more massive than protons
Atoms of different elements have _______ number of protons

Atoms of the same element all have the _________ number of protons

What parts of Daltons theory are not correct
Atoms can be divisible into even smaller particles

Elements can have atoms with different masses
State 5 points of Dalton's Atomic Theory. Whats the date of this theory
1. All matter is composed of atoms

2. Atoms of a element have the same size, mass, Atoms of different elements differ in size, mass etc.

3. Atoms cannot be subdivided, created and destroyed

4. Atoms of a different elements combine in simple whole number ratios to form chemical compounds

5. In chemical reactions atoms are combined, seperated, rearranged
Earliest particle theory of matter was discovered by _________ in __________

He called this particle _________

400 b.c.

Molar Mass (unit)
The mass of a pure substance

How do you define the radius of an atom
Distance from the center of the nucleus to the outer portion of this electron cloud
When was it revealed that the electron has a negative charge

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