alma 6th grade atomic theory

Atom

The atom is the fundamental unit of matter.

Elements

Elements are made up of atoms.

Atomic theory

The study of how atoms are composed is called atomic theory.

Atomos

We get the word atom from Greek- atomos- which means “uncuttable.”

John Dalton

Atomic theory started with a scientist named John Dalton.

1808

In 1808, he published the principles of atomic theory.

Dalton's first principle of atomic theory

Elements are made of extremely small particles called atoms.

Dalton's second principle of atomic theory

Atoms of a given element have the same properties.

Dalton's third principle of atomic theory

Atoms cannot be subdivided, created or destroyed.

Dalton's fourth principle of atomic theory

In chemical reactions, atoms are combined, separated or rearranged.

JJ Thomson

JJ Thomson was responsible for discovering the electron in 1899, and Ernest Rutherford discovered the proton in 1917.

Ernest Rutherford

JJ Thomson was responsible for discovering the electron in 1899, and Ernest Rutherford discovered the proton in 1917.

Gold foil experiment

Rutherford conducted an experiment with gold foil that showed the majority of the mass of the atom was located in the center of the atom, called the nucleus.

Nucleus

The protons and neutrons reside in the nucleus, or center, of the atom.

Current atomic theory

As a result of the work of these scientists, we have a current atomic theory which is both accurate and reflects the ways atoms behave.

Three fundamental particles

From decades of research about the atom, we have discovered that the atom consists of three fundamental particles: the proton, the neutron and the electron.

Proton

Protons carry a positive charge.

What determines which element an atom is?

The number of protons determines which element the atom is.

Carbon

Every atom with 6 protons is an atom of carbon.

Lead

Every atom with 82 protons is an atom of lead.

Atoms of the same element

Every atom of the same element has the same number of protons.

Nuclear reactions

Increasing or decreasing the number of protons can only happen through nuclear reactions- fission (breaking apart a nucleus) or fusion (combining nuclei).

Fission

breaking apart a nucleus

Fusion

combining nuclei

Neutron

Neutrons have no charge and are slightly larger than protons.

What do neutrons do in the nucleus?

Neutrons create stability in the nucleus of the atom.

How do neutrons hold protons together?

Neutrons act like glue that hold protons together.

Why are neutrons important?

Without neutrons, atoms could not exist.

Can an element have different numbers of neutrons?

An element can have a different number of neutrons and still be the same element.

Stable combinations of neutrons

In fact, most elements have multiple different combinations of neutrons which are stable.

Electron

Electrons carry a negative charge and are much smaller than a proton.

Electrical charge of an electron compared to a proton

Even though electrons are much smaller than protons, they have an equal but opposite electrical charge than the proton.

Electron shells

Electrons move around the nucleus in paths called shells.

Neutral charge

An atom will usually have an equal number of protons and electrons. This equal amount gives the atom a neutral charge, meaning it is not positive or negative.

How can atoms lose electrons?

Occasionally, atoms can lose electrons by giving them to other atoms.

How can atoms gain electrons?

Atoms can also gain electrons by stealing them from other atoms.

Periodic table of elements

We have a method of organizing all the elements in the world with a very useful tool: the periodic table of elements.

What is the periodic table?

The periodic table is divided up like a grid and contains every element known to humans.

Information on the periodic table

The periodic table has lots of useful information on the elements. The periodic table is easy to read and understand.

Atomic number

how many protons are in the atom

Atomic mass

the combined weight of all protons, neutrons and electrons in the atom (this is oversimplified, but accurate)

Chemical symbol

the abbreviation for the element

What are the three particles of the atom?

the proton, the neutron and the electron

What atomic particle has a negative charge?

Electrons carry a negative charge and are much smaller than a proton.

What atomic particle has a positive charge?

Protons carry a positive charge.

What atomic particle has no charge?

Neutrons have no charge and are slightly larger than protons.

Who was the first scientist to form the idea of an atom?

John Dalton

Who was the scientist who discovered the nucleus?

Ernest Rutherford

What is atomic number?

how many protons are in the atom

What is atomic mass?

the combined weight of all protons, neutrons and electrons in the atom (this is oversimplified, but accurate