Ch. 17 – Properies of Atoms and Atomic Structure I. Structure of the Atom  Symbols  Subatomic particles  Electron cloud model

A. Chemical Symbols  Capitals matter!  Element symbols contain ONE capital letter followed by lowercase letter(s) if necessary. Co vs. CO Metal that forms bright blue solid compounds. Poisonous gas.

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

B. Subatomic Particles  Quarks 6 types 3 quarks = 1 proton or 1 neutron He

A. Orbital  Region where there is 90% probability of finding an electron.  Can’t pinpoint the location of an electron.  Density of dots represents degree of probability.

A. Orbital  Orbitals have different shapes.

B. Energy Levels  Electrons can only exist at certain energy levels.  Low energy levels are close to the nucleus.  Each energy level (n) can hold 2n 2 electrons.

C. Bohr Model Diagrams  Simplified energy levels using Bohr’s idea of circular orbits. e- Maximum e - Level 12e - Level 28e - Level 318e - Level 432e - Lithium Atomic #:3 Mass: 7 # of p:3 # of e:3 # of n:4 p p n n n n p e- Can replace with: 3p 4n

C. Bohr Model Activity  Choose a number between 1 & 18.  Find your element by the atomic number you picked.  Draw a Bohr Model diagram for your element. Round off the mass listed on the table and subtract the atomic # to find the # of neutrons. Abbreviate the # of ‘p’ and ‘n’ in the nucleus.  Have a partner check your drawing.  Repeat with a new element.

II. Masses of Atoms  Atomic Mass  Mass Number  Isotopes

A. Atomic Mass  atomic mass unit (u)  1 u = 1 / 12 the mass of a 12 C atom  1 proton = 1 u 1 neutron = 1 u  1 u = 1.67  g © Addison-Wesley Publishing Company, Inc.

B. Mass Number  Sum of the protons and neutrons in the nucleus of an atom.  Always a whole number.  # of neutrons = mass # - atomic # © Addison-Wesley Publishing Company, Inc.

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

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

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

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

III. The Periodic Table  Mendeleev  Mosely  Organization

A. Dmitri Mendeleev  Dmitri Mendeleev (1869, Russian) Organized elements by increasing atomic mass. Predicted the existence of undiscovered elements.

B. Henry Mosely  Henry Mosely (1913, British) Organized elements by increasing atomic number. Fixed problems in Mendeleev’s arrangement.

A. Metallic Character  Metals  Nonmetals  Metalloids

B. Table Sections  Representative Elements  Transition Metals  Inner Transition Metals

B. Table Sections Lanthanides - part of period 6 Actinides - part of period 7 Overall Configuration

C. Columns & Rows  Group (Family)  Period

C. Terms  Valence Electrons e - in the outermost energy level these determine the properties of the elements Elements in the same group have the same # of valence electrons

D. Periodic Trends  Group # = # of valence e - (except He) Families have similar reactivity  Period # = # of energy levels 1A 2A 3A 4A 5A 6A 7A 8A

E. Dot Diagrams  Dots represent the valence e -.  EX: Sodium  EX: Chlorine