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Chapter 3 Atoms and Elements

3.1Classification of Matter

Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

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Learning Goals

Classify matter as pure substances or mixtures. Given the name of an element, write its correct symbol; from the symbol,

write the correct name. Use the periodic table to identify the group and the period of an element

and decide whether it is a metal, nonmetal, or metalloid. Describe the electrical charge and location in an atom for a proton, a

neutron, and an electron. Given the atomic number and the mass number of an atom, state the

number of protons, neutrons, and electrons. Give the number of protons, electrons, and neutrons in the isotopes of an

element. Given the name or symbol of one of the first 18 elements in the periodic

table, write the electron arrangement and use it to explain the periodic law.

Use the electron arrangement of elements to explain periodic trends.

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Matter

Matter is the “stuff” that makes up all things.

Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

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A pure substance is classified as

• matter with a specific composition.

• an element when composed of one type of atom.

• a compound when composed of two or more elements combined in a definite ratio.

Pure Substances

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Elements

Elements are • pure substances that

contains atoms of only one type.

Copper, Cu

Lead, Pb

Aluminum, Al

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Compounds

Compounds

• contain two or more elements in a definite ratio.

Salt (NaCl)

Table sugar (C12H22O11)

Water (H2O)

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Elements in a Compound

“Table salt” is a compound that contains the elements sodium and chlorine.

Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

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Mixtures

A mixture is a type of matter that consists of• two or more substances that are physically mixed, not

chemically combined.• two or more substances in different proportions.• substances that can be separated by physical

methods.

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Physical Separation of A Mixture

Example:

Pasta and water are separated with a strainer.

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Homogeneous Mixtures

In a homogeneous mixture,

• the composition is uniform

throughout.• the different parts of the

mixture are not visible.

Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

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Heterogeneous Mixtures

In a heterogeneous mixture, • the composition of

substances is not uniform.• the composition varies from

one part of the mixture to another.

• the different parts of the mixture are visible.

Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

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Classification of Matter

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Identify each of the following as a pure substance or a mixture.

A. pasta and tomato sauce

B. aluminum foil

C. helium

D. air

Learning Check

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Identify each of the following as a pure substance or a mixture.

A. pasta and tomato saucemixture

B. aluminum foil pure substance

C. helium pure substance

D. air mixture

Solution

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Identify each of the following as a homogeneous orheterogeneous mixture:

A. hot fudge sundae

B. shampoo

C. sugar water

D. peach pie

Learning Check

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Identify each of the following as a homogeneous orheterogeneous mixture:

A. hot fudge sundae heterogeneous mixture

B. shampoo homogeneous mixture

C. sugar water homogeneous mixture

D. peach pie heterogeneous mixture

Solution