# I. Structure of the Atom Dalton’s Atomic Theory Subatomic Particles

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I. Structure of the Atom Dalton’s Atomic Theory Subatomic Particles
Ch. 4 - Atomic Structure I. Structure of the Atom Dalton’s Atomic Theory Subatomic Particles

A. Dalton’s Atomic Theory
Every element is made of tiny, unique, particles called atoms that cannot be subdivided. Atoms of the same element are exactly alike. Atoms of different elements can join to form molecules.

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

Atomic Number = # of Protons & Electrons Atomic Mass = # of Protons
B. Subatomic Particles Element Symbol 10 Atomic Number = # of Protons & Electrons Ne Element Name Neon Atomic Mass = # of Protons + # of Neutrons 20.179

B. Subatomic Particles Atoms have no overall charge because the protons (+) cancel out the electrons (-). Neon 10 protons = +10 10 neutrons = 0 10 electrons = -10 total charge 0

II. Electron Cloud Model Orbital Energy Levels Bohr Model Diagrams
Ch. 4 - Atomic Structure II. Electron Cloud Model Orbital Energy Levels Bohr Model Diagrams

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 a certain number of electrons.

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

C. Bohr Model Diagrams Simplified energy levels using Bohr’s idea of circular orbits. Can replace with: 3p 4n Lithium Atomic #: 3 Mass: # of p: 3 # of e: 3 # of n: 4 e- e- p n Maximum e- Level 1 2e- Level 2 8e- Level 3 18e- Level 4 32e- e-

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 on your marker board. Round off the atomic 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.

III. Masses of Atoms Atomic Mass Mass Number Isotopes
Ch. 4 - Atomic Structure III. Masses of Atoms Atomic Mass Mass Number Isotopes

A. Atomic Mass atomic mass unit (amu) – unit of measurement
Average atomic mass – the average mass of all the isotopes of the atom. © Addison-Wesley Publishing Company, Inc.

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

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