Atoms, History & Basic Structure - Mr. Stange (2020)

The History of Atoms

How our understanding keeps changing

Our Understandings of the Atom

• Atoms are the basic building block of all matter.

• Atoms are made of electrically- charged particles:

• Protons (positive charge = p⁺)

• Neutrons (no charge = N⁰)

• Electrons (negative charge = e^_)

Multiple Choice

What is the atomic number?

• the number of protons

• the number of protons and neutrons

• the number of neutrons

• the number of protons and electrons

Multiple Choice

If the number of protons equal the number of _____, the atom will have no charge

• protons
• neutrons
• electrons
• nucleus

Multiple Choice

An atoms overall charge is 

• positive 
• depends on its mood 
• neutral 
• negative 

Multiple Choice

Particles in an atom that are neutral and have no charge are 

• negatrons 
• electrons 
• neutrons 
• protons 

How Do We Know?

• Many scientists have contributed to our understanding of atomic structure.

• These scientists performed all kinds of experiments to discover and prove the structure of the atom.

• Scientists are still performing experiments to go deeper and deeper inside the atom

Scientific Discoveries

• Each scientist set out to prove their ideas based on the evidence they uncovered.

• Each discovery led to a better understanding of the atom and more accurate models of the atom:

• 1897: J.J. Thomson discovers the electron

• 1909: E. Rutherford discovers the proton

• 1913: Niels Bohr discovers e^_ shells

• 1926: Schrödinger & Heisenberg discover the Quantum Structure of the Atom

Multiple Choice

Which experiment discovered the nucleus of the atom?

• cathode ray tube

• gold foil experiment

• heisenberg's uncertainty principle

• flame test experiment

Multiple Choice

What is the charge of a neutron?

• +

• -

• neutral

• both + & -

Multiple Choice

What is the charge of a electron?

• +

• -

• neutral

• both + & -

Multiple Choice

Where are the electrons located?

• o outside the nucleus

• o inside the nucleus

• o in the middle of the atom

• o in areas that contribute to the atom's mass

Multiple Choice

Who first discovered that electrons orbit the nucleus in orbits?

• o Dalton

• o Thomson

• o Rutherford

• o Bohr

Multiple Choice

Who performed the famous 'gold foil experiment'?

• o Dalton

• o Thomson

• o Rutherford

• o Bohr

Multiple Choice

Who first came up with the idea of an atom and called them "atomos"?

• o Democritus

• o Thomson

• o Rutherford

• o Bohr

The Bohr Model

• Thanks to Rutherfords' Gold Foil Experiment, scientists knew that:

• The nucleus was positively-charged and tiny and held the Neutrons & Protons.

• The atom was mainly empty space.

• Bohr figured out that electrons exist in regions called electron levels, shells, or orbits and that each level can only hold a specific number of electrons.

The Modern Model

• The Modern Model of the Atom (the Electron Cloud Model), incorporates the best features of many other models:

• Thomson's electrons,

• Rutherfords' tiny, positive nucleus,

• Bohr's electron levels,

• Schrödinger's electron clouds

• So, the modern model has clouds of electrons that exist in specific levels around the nucleus

The Modern Model

• Here, you can see:

• the tiny, positive nucleus

• Electrons existing in Schrödinger's clouds

• Electron clouds organized into Bohr's energy levels (electron shells)

• This model does not show the actual distance between the nucleus and the electrons and between the electron shells.

Multiple Select

Which of the following statemenst about atoms are true?

• Atoms have no charge because they have the same number of protons & electrons

• The Nucleus is huge

• Atoms are mainly empty space.

• Electrons orbit the Nucleus in clouds at specific levels.

Multiple Choice

Which of the following best describes an electron?

• It has no charge and about the same mass as a proton
• It has a negative charge and much less mass than a proton
• It has a positive charge and much more mass than a neutron
• It has a negative charge and about the same mass as a neutron

Multiple Choice

How many electrons does an atom with 8 protons have?

• 8
• 16
• 15.99
• 24

Multiple Choice

In a stable atom the amount of electrons is electron is equal to

• neutrons
• protons
• atomic mass
• neutrons + protons

Multiple Choice

What is the location of the electron?

• the free floating negatively charged electron cloud
• the free floating positively charged electron cloud
• the very dense positively charged electron orbital
• the positively charged very dense nucleus