DO NOW

DO NOWObject A at 40ºC and Object B at 80ºC are

placed in contact with each other. Which statement describes the heat flow between the objects?

1. Heat flows from object A to object B.2. Heat flows from object B to object A.3. Heat flows in both directions between the

objects.4. No heat flow occurs between the objects.

Introduction to Atomic TheoryWilliamsburg High School for Architecture and

DesignMr. Quinn and Ms. Tom

9/17/13

What Do We Already Know?

AIM: What are atoms made of?

Origins of Atomic TheoryAtomic theory was developed by John Dalton

in the mid 1800sHe used a combination of laws from chemical

reactions


Origins of Atomic TheoryJ. J. Thompson developed the first model of

the atomDeveloped from cathode ray tubes“Plum pudding model:” a positive cloud with

negative particles in it


Origins of Atomic TheoryRutherford came up with the next model of

the atomGold foil experimentAtoms are mostly empty space


Origins of Atomic Theory


Parts of the Atom

Particle Mass ChargeProton 1 +1

Neutron 1 0Electron 0 -1


WAIT! Are you ready?


Exploring Atomic TheoryAtoms start with a charge of zero. What does

that mean for the number of protons and electrons in an atom?They are the same!

Each element is identified by a unique atomic number. The atomic number is equal to the number of protons. What is the relationship between the atomic number and the number of electrons?They are the same!


Exploring Atomic TheoryDo positive and negative charges attract or

repel each other?Electrons orbit the nucleus like the earth

orbits the sun. Why doesn’t the earth fall into the sun? Electrons don’t fall into the nucleus for the

same reasonThey are orbiting too quickly


Exploring Atomic TheoryThe other number in each box on the periodic

table is the atomic mass. For the small elements, what do you notice about its relationship to the atomic number?It is about double

If the atomic number is set and electrons don’t have a mass, what makes up the balance?Neutrons

What is the relationship between the number of protons and neutrons for most elements?They are about equal


Exploring Atomic TheoryDo similar charges attract or repel each

other?Repel

So would a bunch of protons in the nucleus attract or repel each other?RepelIt is neutrons that hold them together.


WAIT! Are you ready?


Problem #1The mass of a proton is approximately equal

to the mass of1. an alpha particle2. an electron3. a neutron4. a positron


Problem #2What is the mass number of a carbon atom

that contains six protons, eight neutrons, and six electrons?

1. 62. 83. 144. 20


Problem #3Which two particles make up most of the

mass of a hydrogen-2 atom?1. electron and neutron2. electron and proton3. proton and neutron4. proton and positron


Problem #4Which statement about one atom of an

element identifies the element?1. The atom has 1 proton.2. The atom has 2 neutrons.3. The sum of the number of protons and

neutrons in the atom is 3.4. The difference between the number of

neutrons and protons in the atom is 1.


Problem #5What is the charge of the nucleus of an

oxygen atom?1. 02. –23. +84. +16


DO NOW

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