unit 2 lesson 4 the atom copyright © houghton mifflin harcourt publishing company

Unit 2 Lesson 4 The Atom

Copyright © Houghton Mifflin Harcourt Publishing Company


Indiana Standards


• 8.1.1 Explain that all matter is composed of particular arrangements of atoms of approximately one hundred elements.

• 8.1.6 Describe the structure of an atom and relate the arrangement of electrons to how that atom interacts with other atoms.

The Atom

Bell work 1/25What is an atom? Which

particles are located in the nucleus?

Big Idea: What makes up an atom?

SWBAT describe the atomic theory by identifying atoms and the parts that make them up.

Why? Atoms make up everything never trust them.

Process Chart of the development of the atomic theory. Look at pages 120-121 and list the scientist and their contributions to the atomic theory. Should have six boxes.

Democritus (eventually you will end up with a particle thatcannot be cut).

Aristotle

Bell work 1/25

As a Matter of Fact …


What is matter made of?• The Greek philosopher Democritus thought matter

could be divided into smaller and smaller units he called atomos.

• In 1803, John Dalton proposed that all substances are made of atoms that cannot be divided.


What is matter made of?• In 1897, J. J. Thomson performed experiments that

detected smaller particles within atoms, (electrons).

• In the early 1900s, Ernest Rutherford (protons/nucleus) and James Chadwick (neutron) revealed the nature of the dense center of an atom.

Today we have the electron cloud model.



Why has the atomic model changed over time?

What are atoms?• An atom is the smallest particle into which an

element can be divided and still be the same substance.

• In 1808, John Dalton published an atomic theory that said all atoms of a particular element are identical.

• Dalton also said that atoms of an element differ from atoms of other elements.



Iron is an element. What is the smallest particle of Iron that has the same chemical properties of iron?

A molecule that contains ironAn atom of ironAn electron from an iron atom

Up and Atom!


What are the parts of an atom?• Atoms are made of protons, neutrons, and

electrons.

• Protons are positively charged particles.

• The mass of a proton is given in the atomic mass unit (u). One proton has a mass of 1 u.


What are the parts of an atom?• Neutrons are particles that have no electrical

charge.

• In most atoms, there are at least as many neutrons as protons.

• The mass of a neutron is slightly more than a proton but is still considered to be 1 u.



What are the parts of an atom?• The nucleus is the at the center of the atom and

contains the protons and neutrons.

• The overall charge of the nucleus is equal to the number of protons in the nucleus.

• The nucleus is small but very dense.



What are the parts of an atom?• Electrons are negatively charged particles.

• Electrons move around the nucleus very quickly in a region called the electron cloud.

• Electrons are very small compared to protons and neutrons.



What are the parts of an atom?• Why is the exact location of an electron hard to

identify?



What are the parts of an atom?• The number of protons and electrons in an atom

are the same, so the charges are balanced.

• An atom can gain or lose electrons to become an ion, which has a net positive or negative charge.



Argon has an atomic number of 18. How many electrons does argon have?

Aluminum has an atomic number of 13. How many electrons does aluminum have?

Take a minute to draw and label the parts of an atom. Show the particles charge.

Take a Number!


How can we describe atoms?• Different combinations of protons, neutrons, and

electrons produce atoms with different properties.

• The number of each kind of particle within an atom determines its unique properties.


How can we describe atoms?• The number of protons distinguishes the atoms of

one element from the atoms of another.

• The number of protons in the nucleus of an atom is the atomic number of that atom.



An atom that has 6 protons is a carbon atom. Which statement best describes what would happen if a proton were added a carbon atom?

The atom would have a negative chargeThe atom would lose electronsThe atom would no longer be carbon

The atomic number for lead is 82. How many protons does lead have? Electrons?

The atomic number for sulfur is 16. How many electrons does sulfur have?

How can we describe atoms?• Atoms of an element have the same number of

protons, but the number of neutrons may differ.

• Isotopes are atoms of the same element that have different numbers of neutrons.

• The total number of protons and neutrons in an atom’s nucleus is its mass number.



The atomic number for mercury is 80 and the mass number is 200. How many neutrons does mercury have?

The atomic number for sodium is 11 and the mass number is 23. How many neutrons does sodium have?

Boron has a mass number of 11 and has 6 neutrons. What is boron’s atomic number?

unit 2 lesson 4 the atom copyright © houghton mifflin harcourt publishing company

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