Unit 3 Lesson 5 Atoms and Elements Copyright © Houghton Mifflin Harcourt Publishing Company.

Unit 3 Lesson 5 Atoms and Elements

Copyright © Houghton Mifflin Harcourt Publishing Company

A Small World


What are atoms?

• All matter is made up of very small particles called atoms.

• Atoms are the basic building blocks of matter, because they are the smallest particles that can have the same properties as the stuff they make up.

• The substances we encounter every day are made up of different atoms combined in different ratios.


What are the parts of an atom?

• Atoms contain even smaller particles called subatomic particles.

• Protons are subatomic particles that have a positive electric charge. They are found at the center, or nucleus, of the atom.

• The nucleus also contains another type of subatomic particle called neutrons. They have no charge.



What are the parts of an atom?

• The protons and neutrons in the nucleus make up most of the mass of an atom.

• The third type of subatomic particles are called electrons, they are negatively charged and are much smaller than protons and neutrons.

• Electrons are found outside the nucleus in a region called the electron cloud.



Nanotechnology


• Nanotechnology is the use of materials and processes designed on the atomic scale.

• In nanotechnology manufacturing, materials are built by putting atoms together.

• Scientists don’t yet know all the possible uses of nanotechnology. Someday, tiny robots may be able to deliver medicine exactly where it is needed to treat disease.


The Element of Surprise


What is an element?

• An element is a pure substance that is made up of only one type of atom.

• An atom is the smallest unit of an element that has the properties of that element.


How are elements described?

• Each element has its own properties that differ from those of other elements. They can be identified by their atomic numbers and chemical symbols.

• Atoms of one element differ from atoms of another element by the number of protons they have. The atomic number of an element is the number of protons in the nucleus of one of its atoms.



How are elements described?

• Elements can also be described by their chemical symbols. A chemical symbol is an abbreviation that represents an element.

• These symbols are like nicknames that allow chemists to write chemical names in a shorter form.



The Head of the Class


What are the three main classes of elements?• The periodic table contains three main classes of

elements: metals, nonmetals, and metalloids.

• A physical property is a characteristic of a substance that can be observed and measured without changing the identity of the substance.

• Most elements are classified as metals, they appearto the left of the zigzag lineon the periodic table.


What are the three main classes of elements?• Most metals are solid and can be recognized by their

luster, or shine. They are good conductors of electric current and of energy in the form of heat.

• Nonmetals appear to the right of the zigzag line on the periodic table.

• Many nonmentals are gases at room temperature. They are typically dull, or lack luster. They are poor conductors of electric current and of energy in the form of heat.



What are the three main classes of elements?• Metalloids appear between metals and nonmetals

along the zigzag line on the periodic table.

• They are elements that have some properties of metals and some properties of nonmetals.

• Metalloids are typically solids and have a somewhat metallic luster.

• They conduct electric current better than nonmetals but not as well as metals.



Elements in Our World


What elements make up Earth?

• Nine elements account for almost all of the matter that makes up our planet.

• These elements are oxygen, silicon, aluminum, calcium, sodium, potassium, magnesium, nickel, and iron. Iron makes up one-third of Earth’s mass.

• Earth has three layers: the crust, the mantle, and the core.


What elements make up Earth?

• The main elements in the crust are oxygen, silicon, and aluminum.



• Earth’s mantle is made of rock that is so hot it flows slowly. Most of the rock is made of silicon, oxygen, iron, and magnesium.

• The main elements in Earth’s core are the metals iron and nickel.

What elements make up the atmosphere and ocean?• The atmosphere is a layer of gases surrounding

Earth.

• It is composed of 78% nitrogen and 21% oxygen. The remaining 1% is made up of gases such as argon, helium, neon, and carbon dioxide.

• The ocean is mainly water. Water molecules are made of hydrogen and oxygen atoms joined together.



What elements make up the atmosphere and ocean?• The ocean is mainly water. Water molecules are

made of hydrogen and oxygen atoms joined together.

• Ocean water contains about 30 elements. The salts in the ocean contain the elements sodium, chlorine, sulfur, magnesium, calcium, and potassium.



What elements make up living things?

• All living things, and things that were once alive, contain the element carbon.

• Other elements abundant in living things include hydrogen, oxygen, nitrogen, phosphorus, and calcium.

• Living things need a variety of other elements, including iron. You can get some of these elements from the food you eat.



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Unit 3 Lesson 5 Atoms and Elements Copyright © Houghton Mifflin Harcourt Publishing Company.

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