Atomic Structure I Structure of the Atom Chemical

Atomic Structure I. Structure of the Atom Chemical Symbols ¨ Subatomic Particles

p. 270 QUIZ ON Thursday 9/13 A. Chemical Symbols ¨ Capitals matter! ¨ Element symbols contain ONE capital letter followed by lowercase letter(s) if necessary. Metal that forms bright blue solid compounds. Co vs. CO Poisonous gas.

B. Subatomic Particles ATOM NUCLEUS ELECTRONS PROTONS NEUTRONS POSITIVE CHARGE NEUTRAL CHARGE Most of the atom’s mass. NEGATIVE CHARGE in a neutral atom Atomic Number equals the # of protons

C. Atomic Mass ¨ atomic mass unit (amu) ¨ 1 u = 1/12 the mass of a 12 C atom ¨ 1 proton = 1 u 1 neutron = 1 u ¨ Mass of proton and neutron are basically the same. © Addison-Wesley Publishing Company, Inc.

The mass of an electron is so small that it is not counted in the Atomic Mass!

D. Atomic Number ¨ Number of protons only! ¨ Identifies the type of element ¨ If it has a different # of protons it is a different element. ¨ Atomic Number is on the Periodic Table. ¨ In a neutral atom protons=electrons

E. Mass Number ¨ Sum of the protons and neutrons in the nucleus of an atom. ¨ Always a whole number. © Addison-Wesley Publishing Company, Inc. ¨ Mass # = protons + neutrons

F. Isotopes ¨ Atoms of the same element with different numbers of neutrons. ¨ Isotope symbol: Mass # Atomic # “Carbon-12”

F. Isotopes © Addison-Wesley Publishing Company, Inc.

C. Isotopes ¨ Average Atomic Mass • reported on Periodic Table • weighted average of all isotopes Avg. Atomic Mass

C. Isotopes ¨ EX: About 8 out of 10 chlorine atoms are chlorine-35. Two out of 10 are chlorine-37. Avg. Atomic Mass 35. 4 u