Download 6-2 Notes: The Atom

6-2 Notes: The Atom
Almost all kinds of atoms are made of the same three particles. These particles are
protons, neutrons, and electrons. They are known as subatomic particles because
they are much smaller than an atom. The number of subatomic particles in an atom
and the way they interact determine the properties of the atom.
Protons are positively charged particles of the nucleus. The SI unit that describes
the mass of a particle in an atom is the atomic mass unit (amu). Each proton has a
mass of about 1 amu. Neutrons are the particles of the nucleus that have no electric
charge. The mass of a neutron can be thought of as 1 amu. Protons and neutrons
are the most massive particles in an atom. The volume of the nucleus is very small.
So, the nucleus is very dense.
Electrons are the negatively charged particles in atoms. They are found outside the
nucleus in electron clouds. It takes more than 1,800 electrons to equal the mass of
1 proton. The mass of an electron is so small that it is usually thought of as almost
zero.
The charges or protons and electrons are opposite but equal, so the charges cancel
out. If the numbers of electrons and protons become unequal, the atom becomes a
charged particle called an ion. An atom that loses one or more electrons becomes a
positively charged ion. An atom that gains one or more electrons becomes a
negatively charged ion.
There are more than 110 different elements. The atoms of each element are
different from atoms of all other elements.
The number of protons in the nucleus of an atom is the atomic number of that
atom. All atoms of the same element have the same atomic number. Isotopes are
atoms that have the same number of protons but have different numbers of
neutrons. Atoms that are isotopes of each other are always the same element,
because isotopes have the same number of protons. They have different numbers of
neutrons, however, which gives them different masses.
An unstable atom is an atom with a nucleus that will change over time. This type
of isotope is radioactive. Radioactive atoms spontaneously fall apart after a certain
amount of time, giving off smaller particles and energy. Isotopes of an element
share most of the same chemical and physical properties.
The mass number is the sum of the protons and neutrons in an atom. You can
calculate the number of neutrons in an atom by subtracting the atomic number
from the mass number. The atomic mass of an element is the weighted average of
the masses of all the naturally occurring isotopes of that element.
Unit 3 (Ch.6) – Atom/Periodic Table
Bach
10//05/09
The forces at work in atom are gravitational force, strong force, electromagnetic
force, and weak force.
Section 6-2 Review
1. What are the three subatomic particles that make up an atom?
Protons, neutrons, and electrons.
2. List the charge and location for each subatomic particle.
Protons: + charge, nucleus
Neutrons: 0 charge, nucleus
Electrons: - charge, electron cloud
3. Describe an atom that has 8 protons, 8 neutrons, and 10
electrons.
An atom with 8 protons would be an oxygen atom, but with 10 electrons
it would be a negative ion with an overall charge of -2.
4. What is an atom’s atomic number equal to?
The number of protons in the nucleus of the atom.
5. How do isotopes of the same element differ from one another?
Isotopes of the same element differ from one another in the number of
neutrons in the nucleus of the atom.
6. How can you determine the mass number of an atom?
The mass number is the sum of the protons and neutrons in the nucleus
of an atom.
7. How many neutrons are in an atom that has a mass number of
51 and an atomic number of 23?
Subtracting the number of protons (atomic number) from the mass
number gives the number of neutrons in the nucleus of an atom: 28.
8. What are the four forces at work in an atom?
The forces at work in atom are gravitational force, strong force,
electromagnetic force, and weak force.
Unit 3 (Ch.6) – Atom/Periodic Table
Bach
10//05/09
6-2 Notes: The Atom
Almost all kinds of atoms are made of the same _______ particles. These particles
are protons, _________, and electrons. They are known as____________ particles
because they are much smaller than an atom. The number of subatomic particles in
an atom and the way they interact determine the _____________ of the atom.
__________ are positively charged particles of the nucleus. The SI unit that
describes the mass of a particle in an atom is the ________ ______ unit (amu).
Each proton has a mass of about _______. __________ are the particles of the
nucleus that have no electric charge. The _______ of a neutron can be thought of
as 1 amu. Protons and neutrons are the most __________ particles in an atom. The
___________ of the nucleus is very small. So, the nucleus is very ___________.
____________ are the negatively charged particles in atoms. They are found
outside the nucleus in electron __________. It takes more than ________ electrons
to equal the mass of 1 proton. The mass of an electron is so small that it is usually
thought of as almost _________.
The charges or protons and electrons are opposite but _________, so the charges
cancel out. If the numbers of electrons and protons become unequal, the atom
becomes a charged particle called an ______. An atom that loses one or more
electrons becomes a _______________ charged ion. An atom that gains one or
more electrons becomes a ______________ charged ion.
There are more than 110 different _____________. The atoms of each element are
_____________ from atoms of all other elements.
The number of protons in the nucleus of an atom is the _________ __________ of
that atom. All atoms of the same ____________ have the same atomic number.
Isotopes are atoms that have the same number of protons but have different
numbers of ___________. Atoms that are ____________ of each other are always
the same element, because isotopes have the same number of protons. They have
different numbers of neutrons, however, which gives them different ___________.
An unstable atom is an atom with a ___________ that will change over time. This
type of isotope is _______________. Radioactive ______ spontaneously fall apart
after a certain amount of time, giving off smaller particles and energy. Isotopes of
an element ________ most of the same chemical and physical properties.
The ______ __________ is the sum of the protons and neutrons in an atom. You
can calculate the number of ___________ in an atom by subtracting the atomic
number from the mass number. The atomic mass of an element is the weighted
average of the __________ of all the naturally occurring isotopes of that element.
Unit 3 (Ch.6) – Atom/Periodic Table
Bach
10//05/09
The forces at work in atom are gravitational force, __________ force,
electromagnetic force, and weak force.
Section 6-2 Review
1. What are the three subatomic particles that make up an atom?
2. List the charge and location for each subatomic particle.
3. Describe an atom that has 8 protons, 8 neutrons, and 10
electrons.
4. What is an atom’s atomic number equal to?
5. How do isotopes of the same element differ from one another?
6. How can you determine the mass number of an atom?
7. How many neutrons are in an atom that has a mass number of
51 and an atomic number of 23?
8. What are the four forces at work in an atom?
Unit 3 (Ch.6) – Atom/Periodic Table
Bach
10//05/09