REVIEW:What is the Electron Cloud

Model?

REVIEW:What is the Electron Cloud

Model?• Model of the atom that pictures the

electrons moving around the nucleus in a region called an electron cloud.

• The electron cloud is a cloud of varying density surrounding the nucleus.

• The varying density shows where an electron is more or less likely to be.

• Atoms with electrons in higher energy levels have additional electron clouds of different shapes that also show where those electrons are likely to be.

For more information, click here: http://regentsprep.org/Regents/physics/phys05/catomodel/cloud.htm

Atomic Structure

What are atoms?

What are atoms?

• An atom is the smallest particle of an element that retains the chemical identity of that element.

• All matter is composed of building (bonding) several atoms together

• An atom is also considered the smallest form of matter

• An element is a pure substance that cannot be broken down into smaller pieces.

What are the 3 major parts of an

atom?

1. Protons 2. Neutrons3. Electrons

*these are referred to as subatomic particles*they are in charge of the main characteristics of an

element

What are the 3 major parts of an

atom?

Draw a diagram showing the location of each part of

the atom.

Draw a diagram showing the location of each part of

the atom.

Add the charges of each part of the atom to your drawing.

Add the charges of each part of the atom to your drawing.

Describe a Proton

Describe a Proton• Protons are positively charged particles

found in the atomic nucleus.

• Discovered by Ernest Rutherford

• Experiments in the late 1960’s/early 1970's showed that protons are made from other particles called quarks. – Protons are made from two 'up' quarks and one

'down' quark.

Describe a Neutron

Describe a Neutron

• Neutrons are uncharged particles found in the atomic nucleus.

• Discovered by James Chadwick in 1932.

• Neutrons are made from one 'up' quark and two 'down' quarks.

Describe an Electron

Describe an Electron

• Electrons are negatively charged particles that surround the atom's nucleus.

• Discovered by J. J. Thomson in 1897.

• Electrons determine properties of the atom. – Chemical reactions involve sharing or

exchanging electrons.

Describe Nucleus

Describe Nucleus

• The nucleus is the central part of an atom.

• It is composed of protons and neutrons.

• The nucleus contains most of an atom's mass.

• It was discovered by Ernest Rutherford in 1911.

Describe Quark

Describe Quark

• What: the basic building blocks of matter.

• When: discovered in experiments done in the late 1960's and early 1970's.

• Kinds: Three families (ea. contains two quarks)

1. Up and Down quarks. Lowest masses. 2. Stable and most common. Form protons &

neutrons.3. Strange and Charm quarks. Only exist at high

energies such as cosmic rays.4. Top and Bottom quarks. Only exist at very high

energies such as cosmic rays.

Orbits

Orbits and Electrons Discovered by Neils Bohr Shells:

① Shell=2 electrons② Shell=8 electrons③ Shell=18 electrons④ Shell=32 electrons

Electrons are responsible for determining the properties of an atom.

Shared or lost to form Ionic or Covalent Bonds. Valence Electrons: Electrons on the outermost

shell.

Describe Isotope

Describe Isotope

Atoms that have the same number of protons but different numbers of

neutrons

Describe Isotope

Example:

http://education.jlab.org/glossary/isotope.html

Atomic Mass and Number• The number of protons tells you what type of

atom you have and vice versa – E.g. every carbon atom has 6 protons and every

atom with 6 protons are carbon atoms

• The number of protons in an atom is equal to a number called the atomic number– The atomic number of carbon is ______

• The atomic mass of an atom is the sum of the number of protons and the number of neutrons in the nucleus of an atom

• Elements are often symbolized with their mass number and atomic number

• These values are given on the periodic table.• For now, round the mass # to a whole number.

• These numbers tell you a lot about atoms…# of protons = # of electrons = atomic number# of neutrons = mass number – atomic number

• Calculate # of e–, n0, p+ for Ca, Ar, and Br.

Atomic Mass and Number

Br

Ar

Ca

e–n0p+MassAtomi

c

3545358035Br

1822184018Ar

2020204020Ca

e–n0p+MassAtomi

c

Closure

1. What are the particles that make up the atom and where are they located?

1. Identify the smallest particle of matter.

1. Where is the majority of the mass of an atom located?

Homework:

• Complete the Atomic Structure and Mass fill-in-the-blanks notes

*I will be checking this for doneness next class!