Atomic Theory and Structure

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Atomic Theory
Atoms are the building blocks of matter.
Law of Definite Proportions
A chemical compound always contains the same elements in the same proportions by mass.
Law of Conservation of Mass
Matter cannot be created or destroyed in ordinary chemical and physical changes.
Law of Multiple Proportions
When 2 elements combine to form 2 or more compounds, the mass of 1 element that combines with a given mass of the other is in the ratio of small whole numbers.
Dalton's Atomic Theory
1. Matter composed of indivisible particles called atoms. 2. Each element's atoms are alike. 3. Atoms of different elements have different masses. 4. Atoms of different elements combine in whole numbers to form compounds. 5. In chemical reactions, atoms are rearranged, not created nor destroyed.
Which principles of Dalton's Atomic Theory are no longer true?
1. Matter composed of indivisible particles called atoms. 2. Each element's atoms are alike.
JJ Thomson
Experimented with cathode ray tube; Discovered electrons
Ernest Rutherford
Experimented with gold foil; Discovered atom is mostly empty space and the nucleus contains most of the atom's mass
The smallest piece of matter than can exist while retaining properties of that matter.
How many types of atoms does an element have?
An element only has 1 kind of atom.
An element has only 1 kind of atom and unique properties.
What charge do atoms have?
Atoms have an electrically neutral charge.
Where is most of the atom's mass contained?
Where are protons and neutrons located?
In the nucleus
Where are electrons located?
In the electron cloud (also referred to as electron shell)
What charge does a proton have?
What charge does a neutron have?
What charge does a neutron have?
No charge
Which 2 subatomic particles have significant masses?
Protons & Neutrons
Coulomb's Law
Like charges repel and unlike charges attract. The closer the charges are, the stronger the force of attraction.
Strong Force
Holds the protons and neutrons together in the nucleus of an atom. The closely packs neutrons and protons creates the strong force which is stronger than the repulsive force.
Atomic Number
The total number of protons in the atom.
What unit is atomic mass measured in?
amu (atomic mass units); 1 amu is 1/12th the mass of one carbon atom
How do you find the atomic mass?
Add the number of protons and neutrons.
Atoms of the same element with different number of neutrons.
What is the mass on the periodic table an average of?
Average of all the isotopes of the elements.
For an atom to be neutral, which two subatomic particles need to be balanced.
Protons and Electrons
Which subatomic particle controls an element's identity?
Negatively charged atom with more electrons than protons
Positively charged particles that have lost electrons.
How can you calculate the charge of an atom?
Protons - Electrons = Charge
Equation for Mass Number
Mass Number = protons + neutrons
What do neutrons affect?
Neutrons affect an atom's mass number.
What do protons affect?
Responsible for an atom's identity, affects mass number, and can affect atom's charge.
What do electrons affect?
Electrons affect an atom's charge.
Which part of the atom has the most mass?
What type of average is "average atomic mass"?
A relative average; it's the average of the isotopes compared to carbon.
Equation for Average Atomic Mass
Average Atomic Mass = (mass of isotope 1 x abundance) + ( mass of isotope 2 x abundance)
What unit can replace amu?
Alpha Particle
A small, positively charge particle, which Rutherford directed at thin, gold foil
The electrode attached to the positive terminal of a voltage source
The electrode attached to the negative terminal of a voltage source