Chapter 4 “Atomic Theory and Structure”

OBJECTIVES: Explain Dalton’s atomic theory. Identify the parts of an atom, their location, charge, and relative mass. Determine the numbers of subatomic particles in an atom.

Democritus’s Atomic Philosophy Democritus created the idea that all matter is made up of various imperishable, indivisible units, which he called atoma. This idea was soon rejected and forgotten.

Dalton’s Atomic Theory All elements are composed of tiny indivisible particles called atoms. 2) Atoms of the same element are identical. Atoms of different elements are different. John Dalton (1766 – 1844)

Atoms of different elements combine in simple whole-number ratios to form chemical compounds In chemical reactions, atoms are combined, separated, or rearranged, but never changed into atoms of another element.

What are the main components of the atom? Atoms have two main regions ________________

One change to Dalton’s atomic theory is that atoms are divisible into subatomic particles: Electrons Protons Neutrons

The Subatomic Particles Location Charge Relative mass in amu Function Proton Neutrons Electrons

Atom Math Protons: atomic number Electrons: protons – charge (same as protons if atom is neutral) Neutrons: mass number – atomic number protons: ________ electrons: ________ neutrons: ________

Atom Math Atomic number: Atomic mass: number of protons (also electrons IF atom is neutral) Atomic mass: Average value of all isotopes called mass number when rounded to nearest whole number Mass Number equals protons + neutrons

Atomic Number Carbon Phosphorus Gold Atomic number of an element is the number of protons in the nucleus of each atom of that element. Element Atomic Number Number of Protons Number of Electrons Number of Neutrons Carbon Phosphorus Gold

Ions When an atom loses or gains electrons it is called an ion Loses—positive ion Gains—negative ion

Ions-counting electrons # electrons gain/lost O -2 Al +3 Be +2 Br -1 K +1

Isotopes Atoms of the same element can have different numbers of neutrons. Thus, different mass numbers.

We can also put the mass number after the name of the element: Naming Isotopes We can also put the mass number after the name of the element: carbon-12 carbon-14 uranium-235 uranium-238

Isotopes are atoms of the same element having different masses, due to varying numbers of neutrons. Protons Electrons Neutrons Nucleus Hydrogen–1 1 Hydrogen-2 (deuterium) Hydrogen-3 (tritium) 2

Isotopes Elements occur in nature as mixtures of isotopes.

Isotopes-counting neutrons Mass # # Neutrons Oxygen-18 Aluminum-25 10Be 79Br Potassium-41

Relative Atomic Mass Atoms are very small particles. It is very difficult to do calculations with the mass of an atom measured in grams. Exmp. The mass of an atom of oxygen is 0.00000000000000000000002657 g. Instead, scientists use a relative unit of mass based on the mass of the nuclide Carbon-12 called the atomic mass unit. Exmp. The mass of an oxygen atom is 16 amu.

How are atomic number, atomic mass, and charge calculated? Mass Number= Protons + ______________ Charge = Protons - _________________

Calculating Protons, Neutrons, and Electrons Neutrons = Mass Number - ________ Electrons = Protons - __________

Complete Symbols Contain the symbol of the element, the mass number and the atomic number. Mass number X Superscript → Atomic number Subscript →

Review Subatomic Particle Counting How many protons, neutrons, and electrons are in Chromium? P = atomic number = 24 N = mass # - protons = 52 - 24 = 28 e = protons – charge = 24 – 0 = 24 How many protons, neutrons, and electrons are in the element with an atomic number of 57? P = atomic number = 57 N = mass # - protons = 139 - 57 = 82 e = protons – charge = 57 – 0 = 57

Chapter 4 Part 2“Isotopes”

Atomic Mass The average atomic mass: is based on the abundance (percentage) of each variety of that element in nature.

To calculate the average atomic mass: Multiply the atomic mass of each isotope by its abundance percentage (expressed as a decimal), then add the results.

Atomic Masses Atomic mass is the average of all the naturally occurring isotopes of that element. Isotope Mass # % in nature Carbon-12 98.89% Carbon-13 1.11% Carbon-14 <0.01% negligible Carbon = 12.011

Average Atomic Mass Rubidium has two common isotopes, Rb-85 and Rb-87. If the abundance of Rb-85 is 72.2% and the abundance of Rb-87 is 27.8%, what is the average atomic mass of rubidium?

On Your Own Titanium has five common isotopes: 46Ti (8.0%), 47Ti (7.8%), 48Ti (73.4%), 49Ti (5.5%), 50 Ti (5.3%). What is the average atomic mass of titanium?

Poll everywhere response Argon has three naturally occurring isotopes: argon-36, argon-38, and argon-40. Based on argon’s reported atomic mass, which isotope do you think is the most abundant in nature?

Calculate the weighted average atomic mass of the following mix of isotopes: Total Number Total Mass Mass of one Atom Percent Abundance (in decimal form) A 15 45 B 5 10

Beanium: Atomic and Isotopic Mass

Purpose: To illustrate the relationship between isotopic mass, isotopic abundance, and atomic mass.

Total # of atoms in sample Weighted average atomic mass for beanium Data Table:   Total mass of sample Total # of atoms in sample Mass of one atom Percent abundance (in decimal form) Isotopic mass Weighted average atomic mass for beanium Black beanium White Spotted beanium Total beanium sample 1

Related Questions: Show all work. 1. Chlorine: a. Chlorine exists in nature as chlorine-35 (% abundance = 75%) and chlorine-37 ( % abundance = 25%). Calculate the atomic mass of chlorine. b. What is the essential difference in the structure between the chlorine atoms found in question Number 1a? 2. Oxygen: Oxygen gas consists of isotopes with atomic masses of 16.00, 17.00, and 18.00 amu. Their abundances are 99.76%, 0.04%, and 0.20% respectively. What is the atomic mass of oxygen? 3. Nitrogen: nitrogen has two isotopes, N-14 and N-15, with masses of amu and amu respectively. If the atomic mass of nitrogen is 14.00674 amu, what is the abundance of each isotope?

Total # of atoms in sample Weighted average atomic mass for beanium Data Table:   Total mass of sample Total # of atoms in sample Mass of one atom Percent abundance (in decimal form) Isotopic mass Weighted average atomic mass for beanium Black beanium White Spotted beanium Total beanium sample 1

Lab Report – Related Questions Chlorine: Chlorine exists in nature as chlorine-35 (% abundance = 75%) and chlorine-37 (% abundance = 25%). Calculate the atomic mass of chlorine. Oxygen: Oxygen gas consists of isotopes with atomic masses of 16.00, 17.00, and 18.00 amu. Their abundances are 99.76%, 0.04%, and 0.20% respectively. What is the atomic mass of oxygen? Nitrogen: nitrogen has two isotopes, N-14 and N-15, with masses of 14.0031 amu and 15.001 amu respectively. If the atomic mass of nitrogen is 14.00674 amu, what is the abundance of each isotope?

Vocabulary Dalton Counting Ions Isotopes Weighted average atomic mass What’s on the quiz? Vocabulary Dalton Counting Ions Isotopes Weighted average atomic mass

Dalton Counting Ions Isotopes Average atomic mass Friday, September 20, 2013 BR: What is the structural difference between Chlorine-35 and Chlorine-37? Dalton Counting Ions Isotopes Average atomic mass

Basic Atomic Theory Review

Basic Atomic Theory Review

Basic Atomic Theory Review

Basic Atomic Theory Review

Quiz Dalton Counting Ions Isotopes Average atomic mass Friday, September 20, 2013 EQ: What characteristics of the atom are explained by the modern atomic theory? Quiz Dalton Counting Ions Isotopes Average atomic mass