The Nature of Matter
Testing Prior Knowledge
• What are the 3 subatomic particles that
make up an atom and their charges?
Particle
a
b
c
Charge
Testing Prior Knowledge
• Draw the basic structure of an atom placing
the subatomic particles in their correct
location.
Testing Prior Knowledge
• What is the atomic number of an atom equal
to?
• What is the atomic mass equal to?
What's the Matter ?
• Matter
– Anything that takes up space and has mass
• Think about solids, liquids and gasses
– Matter is made up of elements
The basic unit of matter
• Atom
Parts of an Atom
• Nucleus –consists of two particles
• Protons + Neutrons
– Located in the center of the atom
Parts of an Atom
• Electrons
– Orbit the nucleus (surround the nucleus)
• In a “cloud” around the nucleus
Charges of Particles
Particle
• Proton
Charge
Positive charge (+)
• Neutron
No charge (neutral)
• Electron
Negative charge (-)
Neutral Atoms
• An atom is neutral when the number of
protons is equal to the number of
electrons
• (protons = electrons)
• Why?
• Because they have opposite charges
and will cancel each other out.
3 electrons and
3 protons
Elements
• Element
– a pure substance that consists entirely of one
type of atom.
Examples: IRON, NICKEL, ALUMINUM
Each Element has a Name and a Symbol
•
•
•
•
•
•
Examples: Essential elements of life
C carbon
H hydrogen
O oxygen
He helium
Pb lead
– The symbol may not always be the first two letters of the word.
Where we find out about all of the elements
Elements are arranged by their
atomic number
• The Atomic Number
– Is equal to the Number of Protons
• (also = to the number of electrons in a neutral atom)
• Atomic Mass (atomic weight)
– Equals the
• Protons + neutrons
Where are the Neutrons?
• Calculating the Number of Neutrons
1. Round atomic mass to a whole
number
2. Subtract the number of protons from
the atomic mass
(remember atomic mass is Protons + neutrons)
If you have the mass and the protons you can
calculate the neutrons
Periodic table practice
Isotopes
• Atoms of the same element that
differ in the number of neutrons.
• (electrons and protons stay the same)
Isotopes
Isotopes can be identified by their atomic mass
They all behave the same chemically
Isotopes of
hydrogen.
The most common
form has no neutrons.
Deuterium has 1 and
Tritium has 2
Atomic mass _______
__________
________
Isotopes
• Unstable atoms are radioactive: their nuclei
change or decay by spitting out radiation, in the
form of particles or electromagnetic waves.
• Radioactive dating is a way scientists use this
decay to date fossils.
Carbon
Dating
Chemical Compound
• A substance formed by the chemical
combination of two or more elements in
definite proportions.
• The study of
Biology deals
mostly with
compounds.
• Notice these
are all made of
individual
elements which
form different
compounds
Nitrogen base
How do we know the
composition of a compound?
The Chemical Formula
• Shows what elements make the compound
• Shows how many of each element make the
compound
Example of a Compound
• Water
– Chemical Formula =
?
H 2O
What is the ratio of the elements?
2 Hydrogen : 1 Oxygen
Example of a Compound
• Sucrose – Table Sugar
• C12H22O11
Ratio of the elements?
• What else can happen when we make a
compound….Look below. Sodium is on the
left and chlorine is on the right.
• If a compound is a combining of
two or more elements, how do they
stay together?
Chemical Bonds
• Hold atoms together
• There are 2 main types
– Covalent
– Ionic
Covalent Bonds
• Formed by….
The SHARING of electrons
Atoms joined by covalent bonds form
molecules
These bonds are strong and flexible
ex. Molecules that form plastics
Covalent bonding of oxygen
•
Covalent Bonds
• Drawing electron shell Diagrams
• Lets look at why atoms would share
electrons
Electron Shell Diagrams
• 1st Shell
Holds 2 electrons
• 2nd Shell
Holds 8 electrons
• 3rd Shell
holds 8 (max 18)
Ionic Bonds
• Formed by….
• The TRANSFERRING of electrons
– The atom that looses an electron is now
positively charged
– The atom that gains the electron is now
negatively charged
• Ions
– Are atoms that have gained or lost an electron
Honors Biology
• Positively charged ions are called
– Cations
• Negatively charged ions are called
– Anions
Cats have paws
– so cations are
“paw –sitive”
Example of an ionic bond
NaCl – Sodium Chloride
• Table salt – these bonds are strong but
brittle – think crystals.
• These form ionic compounds
Review – Types of bonds
Bonds hold atoms together
Covalent
• Electrons are shared
• Form molecules
Ionic
• Electrons are transferred
• Form ions
• Create ionic compounds
• Examples:
• Examples:
– Water
– Carbon dioxide
– oxygen
– Table salt (NaCl)
– Glucose
– Baking soda
• Sodium bicarbonate