SECTION 1: STRUCTURE OF THE ATOMChapter 17: Properties of Atoms

LEARNING GOALSIdentify the names and symbols of common elements.

Identify quarks as subatomic particles of matter.

Describe the electron cloud model of the atom.

Explain how electrons are arranged in an atom.

WARM-UP:Agree or Disagree

SCIENTIFIC SHORTHANDEach element can be symbolized with a chemical symbol.A short or abbreviated way to write the name of an element.

Consist of one capital letter plus one or two small letters.

SCIENTIFIC SHORTHANDSome elements use the first letter or letters of their name to symbolize the element:Aluminum (Al)Calcium (Ca)Carbon (C)Nitrogen (N)

SCIENTIFIC SHORTHANDThe symbols of other elements are derived from Latin:Sodium (Na)Silver (Ag)Gold (Au)Potassium (K)

ATOMIC COMPONENTSAn element is composed of one type of atom.Atom: the smallest piece of matter that still retains the properties of that element.

ATOMIC COMPONENTSAtoms are composed of particles called protons, neutrons, and electrons.

ATOMIC COMPONENTSProtons and neutrons are found in a small, positively charged center called the nucleus.

proton

neutron

ATOMIC COMPONENTSProtons are particles with an electrical charge of 1+They are made up of even smaller

particles called quarks.Different elements have different

numbers of protons

ATOMIC COMPONENTSNeutrons are particles that do not have an electrical charge.They are also made up of even

smaller particles called quarks.The number of neutrons in a single

element may vary

ATOMIC COMPONENTSElectrons are particles with a charge of 1-Electrons are 1/1836

the size of a proton and can be found somewhere in the electron cloud.

The number of electrons in a single element may vary

ATOMIC MODELSAtoms are incredibly small!

It would take 24,400 atoms stacked one on top of another to equal the thickness of a sheet of aluminum foil.

We need models in order to visualize and understand the atom.

ATOMIC MODELS400 B.C.

Democritus proposed the idea that substances were made up of tiny, indestructible particles called atoms.

Aristotle claimed that matter was uniform throughout and could be made of earth, water, air, or fire.Aristotle’s theory was accepted for the next 2,000 years!

ATOMIC MODELS1805:

John Dalton offered proof that atoms exist

Created an early model of the atom that showed a simple sphere

ATOMIC MODELS1926:

The electron cloud model was developed and is still used today

Electron cloud: the area around the nucleus of an atom where its electrons are likely to be found.

ATOMIC MODELSThe electron cloud is 100,000 times

larger than the diameter of the nucleus.

Because electrons are so small and move so quickly, it is impossible to describe their exact locations.

CHECK-IN:Identify the names, charges, and locations of three kinds of particles that make up an atom.