Matter and the
Amazing Atom
WHAT EVERYTHING IN THE WORLD IS
MADE OF !
What’s Chemistry?
• Chemistry is the study of matter.
• Matter is anything that has mass and takes up space (volume). D=m/v
Your turn: Give three
examples of matter in this room.
Note the states of matter.
Atoms
• Matter is made of atoms.
• Atoms are made of even
smaller particles called
protons, neutrons, and
electrons.
• An atom has two main parts: the
nucleus and the electron cloud
that surrounds it.
• Your turn: Make two observations
from this diagram.
The Nucleus- the “kernel”
• An atom is made up of a nucleus
surrounded by one or more electrons.
• The nucleus is the very small center
core of an atom.
• It is made up of smaller particles called
protons and neutrons.
• Protons have a positive (+) electric
charge.
• Neutrons are neutral and have NO (0)
charge.
Your turnProtons are ____________and _________
are neutral.
What does neutral mean?
The Electron Cloud
• The electrons that move rapidly around the
nucleus have a negative(-) electric charge.
• Electrons move rapidly around the nucleus.
• Electrons may be anywhere within the electron
cloud.
http://youtu.be/9qwBfBugo_A?t=44s
Your turn: What are the two main parts of an atom?
What charge does an electron have?
IONS= ++++ Atoms with a Charge----• In a neutral atom, the number of protons = electrons.
• EX. An atom with 4 protons (positive charges) and
electrons (negative charges) has no charge.
4
• The charges cancel out each other, making the atom
neutral.
• If an atom gains electrons, it will be more negative and is
called an anion.
• If an atom loses electrons, it is less negative and is called a
cation.
• An atom with either a positive or negative charge is called
an ion.
• Your turn: what makes an atom neutral? What’s a
positive ion called?
Protons determine the element
•
One atom is different from another atom if it has a different number of
protons
. Hydrogen has only one (1) proton in its nucleus, while carbon has six (6)
protons.
• Hydrogen and carbon are called elements.
• An element is made up of all the same atoms.
• Every atom of an element has the same number of protons.
• The number of protons in the nucleus of its atoms is called the
atomic number. It also tell you the number of electrons in a neutral
atom. . http://www.kscience.co.uk/animations/atom.htm
• So, we would say that the atomic number of hydrogen is 1 and
carbon is 6.
• Your turn: Count the number of protons and electrons in each atom.
Write it down. Are they ions? Why or why not? What is the atomic
number of Lithium? What is the atomic number of Helium?
hydrog
en
Helium
Mass –the measure of matter-Atomic Mass
• Mass is the measure of how much stuff (matter) is in
a substance.
• Atoms are so small their mass is measured in atomic
mass units (amu).
• One proton is about one atomic mass unit. (1 amu).
• One neutron is about one atomic mass unit . (1 amu)
• Together they make up all the mass of an atom.
• The number of all the protons and all the neutrons
combined together is called the
(atomic) mass number.
• Ex. Boron has 5 protons and 6 neutrons. Its (atomic)
mass number is 11 amu
Your turn: If an atom has a mass number
of 12 and an atomic number of 6, how
many neutrons does it have?
The Mass of Electrons
• Electrons are much smaller.
• It takes almost 2,000
electrons to equal the mass of
one proton.
• Electrons, however, take up
much more space in the atom
than the nucleus.
• Your turn: Why is the mass of
electrons not calculated in
the mass number of an
atom?
Figure 4.12: Electrons are much smaller than protons or neutrons.
How much smaller? If an electron was the size of a penny, a
proton or a neutron would have the mass of a large bowling ball!
Isotopes- same element –same atomic number
but different mass number
• All atoms of the same element have the same number of
protons, or same atomic number.
• Sometimes, they may can have different numbers of
neutrons and therefore, have a different mass number.
• Isotopes are atoms with the same number of protons
but a different number of neutrons.
• An isotope is identified by its mass number.
• Your turn: What happens when you change the number
of protons in an atom? What happens when you change
the number of neutrons? What is the mass number for
the first carbon atom?
In an isotope only the number of
neutrons change. The number of
protons stay the same. Why?
Examples of Isotopes
• Hydrogen, has 1 proton and 0 neutrons, its
atomic mass number is 1
(1p +0 n=1amu) and it is called Hydrogen-1.
• An isotope of hydrogen is N atom with 1
proton and 1 neutron and it is called called
Hydrogen-2 (1p+1n=2amu).
• Hydrogen-3 is another isotope.
(1p+2n=3amu).
• The average mass of all the isotopes of an
element is called the atomic mass. (not the
same as (atomic) mass number.)
•
http://phet.colorado.edu/en/simula
tion/isotopes-and-atomic-mass
Your turn: What is the mass number of
an isotope for chlorine (Cl) which has
17 protons and 18 neutrons?
What’s the difference between atomic mass
and (atomic) mass number?
• http://moodle.fct.unl.pt/pl
uginfile.php/61092/mod_b
ook/chapter/948/Yr_8/che
mestry/atoms_and_eleme
nts/nature_matter.swf
• http://phet.colorado.edu/
en/simulation/isotopesand-atomic-mass