4.2 Structure of an Atom Objectives: Identify three subatomic particles and compare their properties Distinguish the atomic number of an element from the mass number of an isotope, and use these numbers to describe the structure of atoms

Subatomic Particles: Protons, Electrons and Neutrons

What is an Atomic Mass Unit? How to find atomic number, mass number and number of electrons within an atom? structure-and-properties/introduction-to-the-atom/v/atomic- weight structure-and-properties/introduction-to-the-atom/v/atomic- weight

Atomic Number & Mass Number Atomic Number Elements are arranged by increasing atomic number on the periodic table. Number of protons Equal to the number of electrons Mass Number Sum of protons and neutrons # of neutrons = mass number – atomic number

Isotopes Atoms of the same element but different number of neutrons Same atomic number Hydrogen-1 has no neutrons Hydrogen-2 has one neutron Hydrogen-3 has two neutrons Water that contains Hydrogen-2 atoms is considered heavy water with slightly different physical properties than ordinary water, see figure 12 pg. 112.

Bookwork Do as homework pgs 105 #1-8 and 112 #1-9 Write the answers in complete sentences.