© 2006 Plano ISD, Plano, TX Atomic Structure

© 2006 Plano ISD, Plano, TX An element is a substance which cannot be broken down into simpler substances under normal circumstances. This means that if you break gold down into smaller and smaller pieces, it will still be gold. Gold is made of nothing... but gold. Gold is an element.

Salt is not an element. Salt can be broken down into simpler substances— Salt is a chemical compound made of sodium and chlorine.

© 2006 Plano ISD, Plano, TX The smallest, tiniest piece of gold is an atom of gold. An atom is the smallest unit of an element.

© 2006 Plano ISD, Plano, TX The smallest particle or piece of gold is an atom of gold. The smallest particle of carbon is an atom of carbon. Carbon is also an element.

© 2006 Plano ISD, Plano, TX All atoms have 2 common structures: nucleus energy level(s)

© 2006 Plano ISD, Plano, TX energy level nucleus electrons+ + protons neutrons- - Each structure is made of subparticles.

© 2006 Plano ISD, Plano, TX The number of protons in the nucleus of an atom is that atom’s atomic number. Gold has 79 protons. The atomic number of gold is ___. Carbon has 6 protons. The atomic number of carbon is The number of protons plus the number of neutrons in the nucleus of an atom is its atomic mass.

© 2006 Plano ISD, Plano, TX Atomic Number = Atomic Mass = Protons = Neutrons = Electrons = Energy Levels = oxygen atom

© 2006 Plano ISD, Plano, TX To find the number of neutrons in an atom, subtract the atomic number from the atomic mass. 16 Atomic mass (protons + neutrons) - 8Atomic number (protons) ___ 8Number of neutrons

© 2006 Plano ISD, Plano, TX N 7 nitrogen G element symbol atomic number state of matter element name atomic mass How many electrons? How many protons? How many neutrons? An example of an entry in the periodic table.

© 2006 Plano ISD, Plano, TX N 7 nitrogen G The atomic mass is always rounded to the nearest whole number to to 27

© 2006 Plano ISD, Plano, TX So far, there are over 100 known elements. A summary of each element’s atomic structure is found in the Periodic Table of Elements. more about that later...