Download Getting to Know: Atomic Structure and Elements

Getting to Know: Atomic Structure and Elements
What is the smallest particle you can imagine? Just as cells are the building blocks of all living
things, atoms are the building blocks of all matter. Atoms come together to form different
substances.
What are atoms?
An atom is a tiny particle that forms the basis of all matter. The word atom comes from the
Greek for cannot cut, because scientists once thought that atoms were the smallest particles
on Earth and that they could not be split into smaller parts. Scientists now know that atoms
are actually made of three subatomic particles.
What are the three subatomic particles that make up an atom?
If you could observe inside an atom, you would first see two types of particles bound together
at the center in the nucleus. These particles are called protons and neutrons. You would then
need to look far away from the nucleus to find the third type of particle, called an electron,
which orbits around the nucleus. Although diagrams usually show electrons orbiting near the
nucleus, in reality electrons orbit relatively far away from the nucleus.
Not all atoms have the same number of these particles. For example, an oxygen atom has only 8 protons, 8 neutrons, and 8 electrons. An atom of silver, on the other hand, contains 47 protons, 61 neutrons, and 47 electrons. Misconception 1: Is it possible to see an atom using a light microscope?
No, light microscopes depend on light particles bouncing off objects. Atoms are too
small for light to bounce off of them, so a light microscope cannot detect individual
atoms. Atoms are so small that they can only be seen using a high-resolution method
called an atomic force microscopy.
What is the difference between a
proton, neutron, and electron?
Look at the diagram of an atom. Notice that each
particle has a different symbol. Protons have a
positive charge, so they are marked with a +.
Electrons have a negative charge and are marked
with a –. Neutrons are marked with a 0 because
they do not have a charge.
The nucleus of an atom contains protons
and neutrons. Electrons orbit the nucleus
at a relatively large distance.
Concept: Atomic Structure and Elements
Getting to Know
www.discoveryeducation.com
1
© Discovery Education. All rights reserved.
Discovery Education is a subsidiary
of Discovery Communications, LLC.
Is the charge the only difference between protons, neutrons,
and electrons?
No, the charge is not the only difference. Electrons also have a much smaller mass than protons and neutrons. The mass of an electron is close to zero.
Can atoms combine?
Yes, atoms combine when they form bonds. An atom forms a bond with another atom by
either gaining or losing electrons. An atom can form a bond with the same kind of atom or
with different kinds of atoms. A substance that is made of only one type of atom is called an
element.
How is an element different than an atom?
An element is a sample of a substance that contains only one type of atom. The element silver
contains only silver atoms. The element gold contains only gold atoms. Not all substances are
elements. For example, bronze is a metal made of the elements copper and tin. Because it
contains two types of atoms, bronze is not an element.
What are some other properties of elements and atoms?
An atom cannot be divided further and still be identified as an atom of a particular element.
For example, if a silver atom were split into protons, neutrons, and electrons, it would no
longer be silver. It would just be a collection of subatomic particles. Scientists have discovered
more than 100 elements so far. These elements have been charted on a table called the
Periodic Table of Elements. This table groups elements based on the characteristics of their
atoms. Although scientists have only discovered approximately 100 elements, theoretically
there may be many more elements still to be discovered.
Can an atom lose any of its particles?
Atoms cannot lose protons or neutrons because they are held together in the nucleus. In some elements, however, the atoms have electrons that are arranged in unstable configurations. These electrons can interact with other atoms. When an electron is gained, lost, or shared, the atoms bond chemically to form a molecule.
Misconception 2: When elements combine, do they only form one type of substance?
Elements can combine in different ways. These combinations can produce substances
with very different characteristics. Carbon is an element. Its atoms combine in one way
to form diamonds, which are shiny and extremely hard. On the other hand, carbon
atoms combine in a different way to form coal, which is dull and very soft.
In this lesson, you will learn more about elements and their atomic structure. When you
understand the way protons, neutrons, and electrons work together to form matter, you will
be on your way to understanding all of chemistry!
Concept: Atomic Structure and Elements
Getting to Know
www.discoveryeducation.com
2
© Discovery Education. All rights reserved.
Discovery Education is a subsidiary
of Discovery Communications, LLC.