1. Atom2. Proton3. Nucleus4. Neutron5. Electron6. Mass number7. Atomic number8. Atomic mass unit9. Isotope

10. Atomic Mass Due Tomorrow!

Atomic Theory Unit Vocabulary• First column:

words• Second column:

definition from text• Third column:

definition in your own words

• Fourth column: Picture or example

SC3. Students will use the modern atomic theory to explain

characteristics of atoms.

“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- all matter is made up of imperishable, indivisible units, which

he called atoma.

Dalton’s Atomic Theory

1)All elements are composed of atoms.

2) Atoms of the same element are identical. Atoms of different elements are different.

John Dalton(1766 – 1844)

3)Atoms of different elements can combine to form compounds.

4) In chemical reactions, atoms are combined, separated, or rearranged, but never changed into atoms of another element.

Modern Theory

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

ElectronsProtons Neutrons

The Subatomic Particles

Location ChargeRelative

mass in amu Function

Proton

Neutrons

Electrons 0.00055 amu

amu: mass of 1/12 of a carbon atom

Atom Math

Atomic number: number of protons (and electrons IF atom is neutral)Atomic mass:

called mass number when rounded to nearest whole number. Mass Number equals protons + neutrons.

Atom Math Protons: atomic number Electrons: same as protons if atom is

neutral Neutrons: mass number – atomic

number

protons: ________neutrons: ________electrons: ________

Element Atomic Number

Number of Protons

Number of Electrons

Number of Neutrons

carbon   

Phosphorus   

Gold

   

Symbol Shorthand

X Massnumber

Atomicnumber

Subscript →

Superscript →

Carbon

Phosphorus

Gold

Work Session

Subatomic Particle Counting WS—15 minutes

Atomic StructurePart 2“Isotopes and Ions”

Ions When an atom loses or gains electrons it

is called an ion. The number of electrons lost or gained is indicated by a charge.

Element

Protons Electrons

Ion

Oxygen Gains 2 electrons

Aluminum Loses 3 electrons

Beryllium Loses 2 electrons

Bromine Gains 1 electron

Assignment

Ion Practice Set

Finish for homework

Ion Review

Element

Number of protons

Number of Electrons

Ion

Sulfur Gains 2 electrons

Sodium Loses 1 electron

Boron loses 3 electrons

Atomic StructurePart 2“Isotopes and Ions”

Isotopes

Atoms of the same element can have different numbers of neutrons.

Thus, different mass numbers.

Naming Isotopes To distinguish between isotopes of the same

element, put the mass number after the name of the element:

AZ Proton

sNeutro

nsOxygen-18

Aluminum-2510Be (beryllium-10)

79 Br (bromine-79)

Potassium-41

X

IsotopesElements occur in nature as mixtures of isotopes.

So, atoms of the same element aren’t necessarily the same….AVERAGE atomic mass

Isotope ReviewProtons Neutrons

Carbon-12

Carbon-14

Uranium-238

Uranium-235

Hydrogen-1

Hydrogen-2

Hydrogen-3

Work Session

Complete Ion Practice Set and Isotope Practice Sets (15 minutes)

Percent Abundance and Average Atomic

Mass

Atomic Mass The average atomic mass: is based on

the abundance (percentage) of each variety of that element in nature.

Lesson Preview

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?

Poll everywhere response

To calculate the average atomic mass:

Multiply the atomic mass of each isotope by it’s

abundance percentage (expressed as a decimal),

then add the results.

Atomic Masses

Isotope Atomic mass

% in nature

Carbon-12 98.89%

Carbon-13 1.11%

Carbon-14 <0.01%negligible

Atomic mass is the average of all the naturally occurring isotopes of that element.

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%), 50Ti (5.3%). What is the average atomic mass of titanium?

Beanium Lab

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

Lab Hints

Read the instructions!Everyone participate in

counting beans.Do not lose your beans and

clean up when you are finished.

Work on the following assignments:◦Beanium Lab◦Average Atomic Mass Practice Worksheet

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