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. Area around the nucleus of an atom where electrons are most likely found Its impossible to describe its exact location because it is so small and moving so quickly around the nucleus (e.g. spokes on a bicycle wheel) For more information, click here: http://regentsprep.org/Regents/physics/phys05/catomodel/cloud.htm

Atomic Structure

What are atoms? What are atoms? The smallest piece of matter that still retains the property of the element. An element is matter that is composed of one type of element. It would take ~24,400 atoms stacked on top of one another to equal the thickness of a sheet of aluminum foil

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 atoms? The smallest piece of matter that still retains the property of the element. An element is matter that is composed of one type of element. It would take ~24,400 atoms stacked on top of one another to equal the thickness of a sheet of aluminum foil

What are the 3 major parts of an atom?

What are the 3 major parts of an atom? Protons Neutrons Electrons *these are referred to as subatomic particles *they are in charge of the main characteristics of an element Particles

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) Up and Down quarks. Lowest masses. Stable and most common. Form protons & neutrons. Strange and Charm quarks. Only exist at high energies such as cosmic rays. Top and Bottom quarks. Only exist at very high energies such as cosmic rays. Quarks are even smaller particles than protons and neutrons Quarks account for the electrical charge of an atom

Orbits

Orbits and Electrons Discovered by Neils Bohr Shells: Shell=2 electrons Shell=8 electrons Shell=18 electrons 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 The nucleus contains most of the mass of the atom because protons and neutrons are far more massive than electrons The mass of a proton is about the same as that of a neutron The electron’s mass is so small that it is considered negligible when finding the mass of an atom (think of adding a paperclip to the top of a textbook) p.512

Atomic Mass and Number 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. DRAW AN EXAMPLE ON THE BACK OF THEIR HISTORY WORKSHEET

Atomic Mass p+ n0 e– Ca Ar Br

Atomic Mass p+ n0 e– Ca 20 40 20 20 20 Ar 18 40 18 22 18 Br 35 80 35 45 35

Closure What are the particles that make up the atom and where are they located? Identify the smallest particle of matter. 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!