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BELL-RINGER QUESTION
1. Look at the periodic table of elements….
How are the elements in the periodic table like the
alphabet of letters?
Today’s Objective:
• Review elements and bonding
(In order to prepare for comparing the structure and
function of bio-molecules)
Can be found in the book:
Pg. 141 - 147
ATOMS
• An atom is the smallest particle of an element
that has the characteristics of that element.
• Atoms are the basic building blocks of all matter.
ATOMS
• The center of an atom is called the nucleus.
• All nuclei contain positively charged particles
called protons (p+).
• Most contain particles that have no charge,
called neutrons (n0).
• There is a region of space that surrounds the nucleus
called the electron cloud.
• In the electron cloud there
are extremely small,
negatively charged particles
called electrons (e-)
ATOMS
Nucleus
8 protons (p+)
8 neutrons (n0)
• Electrons exist
around the nucleus
in regions known
as energy levels.
Oxygen atom
• The first energy level holds 2 electrons.
• The second level holds up 8 electrons.
• The third level can hold up to 18 electrons.
• To know the number of electrons in an energy level
can hold after that, use this formula, 2n²
ATOMS
• The electrons that are in the outer most
energy level for that atom are called
valence electrons.
PRACTICE MAKING ATOMS
ELEMENTS
• Everything – whether it is a rock, frog, or
flower (abiotic or biotic) – is made of substances called
elements.
• An element is a pure substance made only of
one kind of atom. (it cannot be broken down
into a simpler chemical substance)
• Elements differ in the number of protons
– Ex: Carbon has 6 protons : Hydrogen has 1 proton
ELEMENTS
PERIODIC TABLE
5
Atomic Number
B
Atomic Symbol
10.81
Atomic Mass
Atomic Number:
The number of protons in an atom defines what element it is. For example carbon
atoms have six protons, hydrogen atoms have one, and oxygen atoms have
eight. The number of protons in an atom is referred to as the atomic number of
that element.
Atomic Symbol:
The atomic symbol is one or two letters chosen to represent an element ("H" for
"hydrogen," etc.). These symbols are used internationally.
Atomic Mass:
The atomic mass is the sum of protons and neutrons.
ELEMENTS
• Of all the naturally occurring elements on Earth, only
about 25 are essential to living organisms.
• Carbon, hydrogen, oxygen, and nitrogen make up
more that 96 percent of the mass of a human body.
Chemical Bonding
Atoms can join together during
chemical bonding to form
compounds
– A Compound is a substance
made of the joined atoms of
two or more different elements
– Compounds are represented
by a chemical formula that
shows the proportions of each
element in the compound
Covalent bonds
(co = together, valence= outer electrons)
• Covalent bonds occur when two or more atoms share
electrons
A compound made
with covalent bonds is
called a molecule
Hydrogen bonds
– Molecules with an uneven
distribution of electrical
charge like water have poles
and have a polar attraction
– Hydrogen bonds are a
weak chemical attraction
between polar molecules
Water molecules are attracted to each
other by hydrogen bonds
Ionic bonds
• An ion is an atom that
has gained or lost an
electron.
– Ions have a charge
due to the unequal
number of protons and
electrons
• The attractive
force between two
ions of opposite
charge is known as
an ionic bond.
CHEMICAL REACTIONS
• Chemical reactions occur when bonds are formed or
broken, causing substances to recombine into
different substances.
CHEMICAL REACTIONS
• All of the chemical reactions that occur within an
organism are referred to as that organism’s
metabolism.
CHEMICAL REACTIONS
• In a chemical
reaction, substances
that undergo
chemical reactions,
are called reactants.
• Substances formed
by chemical
reactions, are called
products.
In this reaction, what are the reactants and
what is the product?
Question 1
Which of the following is an element?
A. chlorophyll
B. carbon
C. sodium chloride
D. water
Answer
The answer is B.
An element can't be broken down into simpler
chemical substances. Chemical elements
combine in different ways to form a variety of
substances useful to living things.
Question 2
The smallest particle of an element that has the
characteristics of that element is a(n)
__________.
A. proton
C. nucleus
B. electron
D. atom
Answer
The answer is D. Atoms are the basic building
blocks of all matter and have the same general
structure, including a nucleus and electrons.
Elements found in both living and nonliving
things are made of atoms.
Nucleus
Electron energy levels
An atom has a
nucleus and
electrons in
energy levels.
Question 3
Which of the following can contain two types of
particles?
A. nucleus
B. protons
C. neutrons
D. electrons
Answer
The answer is A. The nucleus is the center of
the atom and may contain both positively
charged particles and particles that have no
charge.
Nucleus
8 protons (p+)
8 neutrons (n0)
Oxygen atom