Download Chapter 2.1 and 2.2

Atoms, matter, pH and water
1
atomic # = # of protons
H
hydrogen
1.001
Atomic Mass (amu)
1
H
hydrogen
1.001
Element Symbol
(first letter is always capital
and if a second letter exists
it is lowercase)
Element name
(if name doesn’t match the
symbol it means the
symbol came from its latin
name)
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The elements in Mendeleev’s periodic
table are arranged in rows (left to
right) called periods.
These rows are arranged in order of
increasing atomic mass.
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The elements are also arranged into
columns (up and down) called groups
or families.
The elements within each column have
similar chemical properties for
example similar boiling points and/or
melting points.
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Elements are any substance that
cannot be broken down into simpler
substances. A pure substance that
consists entirely of one type of atom.
Examples:
◦ Hydrogen
◦ Aluminum
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In comparison a compounds is made
up of 2+ different elements.
Combined chemically.
Examples:
◦ Water (H2O)
◦ Sugar (C6H12O6)
Humans are mostly what four
elements (96% of your body)?
 Carbon (C)
 Hydrogen (H)
 Oxygen (O)
 Nitrogen (N)
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 What
are the six elements found
in every living thing?
◦ Carbon (C)
◦ Hydrogen (H)
◦ Oxygen (O)
◦ Nitrogen (N)
◦ Phosphorus (P)
◦ Sulfur (S)
 What
are the other elements
that make up your body called
that are found in small
amounts like copper and
iodine?
◦ Trace Elements!
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An atom is the smallest particle of an element
that has the characteristics of that element
and forms the basic building blocks of all
matter.
In other words, atoms are made up of
electrons, protons, and neutrons.
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Label the atom with the following labels:
◦ Electron
◦ Proton
◦ Neutron
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Label the atom with the following labels:
◦ Electron
◦ Proton
◦ Neutron
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Which 2 particles make up the nucleus of an
atom?
proton and neutron
What are the charges on each of the 3 parts
of an atom?
Electron (e-)
-1
Proton (p)
+1
Neutron (n)
0
 How
is an atom held
together?
◦Opposite charges attract each
other and hold it together.
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The atomic number tells how many protons
an element has.
In a NEUTRAL ATOM:
number of electrons.
Protons equal the
There are non-neutral atoms that do not
follow this rule!
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To determine the number of neutrons:
Atomic mass = (# of protons) + (# of neutrons)
Hint: use algebra to solve for the missing
value!
 Ex: Hydrogen has how many
p ________ n___________ and e-____________
Atomic mass = (# of protons) + (# of neutrons)
Ex: Hydrogen has how many
p
1
n
0
and e-
1
Atomic mass = (# of protons) + (# of neutrons)
1 = (1) +(# of neutrons)
# neutrons = 0
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Using the periodic table that has been provided
to you answer the following three questions:
Q: How many protons, neutrons and electrons are
in He? p =_____, n = _____, e = _____.
Q: How many protons, neutrons, and electrons are
in N? p =_____, n= _____, e = _____.
Q: How many protons, neutrons, and electrons are
in Be? p =_____, n = _____, e = _____.
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Important: The periodic table is reflecting
neutral atoms. We will discuss atoms that are
not neutral later (isotopes and ions)!
Q: How many protons, neutrons and electrons
are in He? p =___2__, n = ___2__, e = __2___.
Q: How many protons, neutrons, and electrons
are in N? p =__7___, n= ___7__, e = ___7__.
Q: How many protons, neutrons, and electrons
are in Be? p =__4___, n = ___5__, e = ___4__.
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A change in the number of protons would
change its atomic number, as well as all of its
chemical properties.
It would be a new element!
PROTON COUNT WILL NOT CHANGE!
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A change in the number of neutrons would
NOT change its chemical properties, but will
affect the mass. An atom with a different
number of neutrons is called an isotope.
A change in the number of electrons would
change its chemical properties, but it will
NOT affect the mass. An atom with a
different number of electrons is called an ion.
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Isotopes occur in nature in very small
amounts. In fact, when atomic masses are
calculated for the periodic table, the masses
of the isotopes are averaged with the
common form.
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Radioactive isotopes have unstable
nuclei and can break down at a
constant rate over time. The
radiation of these isotopes can be
dangerous but they are useful in
biology.
For example,
 Geologists can determine the age of rocks and
fossils.
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The radiation from some isotopes can be used
to detect and treat cancer and some isotopes
can be used as “tracers” to tag and follow
substances inside of an organism.
Electrons
float around
the nucleus in:
Orbitals / Shells /
Electron Clouds /
Energy Levels
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How many electrons are
in the first orbital (inner
shell) of:
C (atomic no. = 6) ____
S (atomic no. = 16) ____
N (atomic no. = 7) ____
P (atomic no. = 15 )____
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How many electrons are
in the first orbital (inner
shell) of:
Each has 2 electrons
1st orbital holds how
many electrons?
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How many electrons are
in the first orbital (inner
shell) of:
Each has 2 electrons
1st orbital holds how
many electrons? 2
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How many electrons are
in the second orbital of:
C (atomic no. = 6) ____
S (atomic no. = 16) ____
N (atomic no. = 7) ____
P (atomic no. = 15 )____
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How many electrons are
in the second orbital of:
C (atomic no. = 6) _4_
S (atomic no. = 16) _8_
N (atomic no. = 7) _5_
P (atomic no. = 15 ) _8_
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The Bohr model rules are as follows:
1st orbital : holds at most 2 electrons
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2nd and 3rd orbital: holds at most 8 electrons
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4th and beyond orbital: holds at most 18
electrons
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1) draw a nucleus (write inside the number of
protons and neutrons)
2) draw the orbitals filling in the correct number
of electrons (until you run out of electrons)
Example: Draw the Bohr model of Lithium
Example: Draw the Bohr
model of hydrogen.
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Example: Draw the
Bohr model of sodium.
 Why
is the Bohr model inaccurate/
outdated?
Because electrons don’t exist in
perfect orbitals. Scientists believe
they exist in clouds.
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Look at the electron configuration of these
first column elements. Explain the trend(s)
you see:
 Look
at the electron configuration
of these first column elements.
Explain the trend(s) you see:
They always have 1 electron sitting
in their outer shell.
 What
are electrons in the
outermost orbital called?
Valence Electrons
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Look at the electron configuration of the
second column elements (Be, Mg, Ca), what
trend(s) do you see? You may want to try
sketching one or two of them out.
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Look at the electron configuration of
the second column elements (Be, Mg,
Ca), what trend(s) do you see? You
may want to try sketching one or two
of them out.
They all have 2 electrons in the
outermost shell.
The numbers above the “A” columns = the
number of valence electrons. These are the
electrons that react with other elements.
1 2
3 4 5 6 7 8
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For now we will ignore the “B” columns
(transition metals) because they react
differently than the 8 main group elements.
How many valence electrons do the following
elements have?
Mg ____________
O ____________
Cl_____________
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How many valence electrons do the following
elements have?
Mg
2
O
6
Cl
7
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Name some atoms that naturally have their
outermost shell filled.
(He) Helium
(Ne) Neon
(Ar) Argon
(Kr) Krypton
These gases are commonly referred to as the
noble gases.
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So what can atoms do to be more like the
noble gases / more stable in terms of their
electrons?
Lose electrons
Gain electrons
Share electrons
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Examples: what do the following need to lose
(or gain) to be “stable”?
Na _________
Be _________
B__________
C__________
N __________
O__________
F_________
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Examples: what do the following need to lose
(or gain) to be “stable”?
Na
lose 1
Be
lose 2
B
lose 3
C
lose or gain 4
N
gain 3
O
gain 2
F
gain 1
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The process of showing how the atoms bond/
come together is represented in a chemical
equations.
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For example, let’s form 2 water molecules.
2H2 + O2  2H2O
What are the substances to the left of the
arrow called? REACTANTS
What are the substances to the right of the
arrow called? PRODUCTS
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Heterogeneous Mixtures are a combination of
substances that when put together the
individual components keep their own
properties.
Give an example of a mixture:
◦ Salad, Trail Mix, Granite Countertop
 Solutions
(aka homogeneous
mixtures) are a combination of
substances that when put together
they are distributed evenly.
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The substance doing the dissolving is
called the solvent and the substance
being dissolved is the solute.
This is easy to remember because
water is often referred to as the
universal solvent.
Give an example of a solution:
Salt Water
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What part of that is the solute?
The solvent?
Give an example of a solution:
Salt Water
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What part of that is the solute?
The solvent?
WATER
SALT
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The pH scale tells the
amount of H+ ions in a
solution.
It is a measure of how
acidic or basic/alkaline
a solution is.
The pH scale ranges
from 0 to 14.
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Substances less than 7
are acidic
substances greater
than 7 are basic
substances at 7 are
neutral
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The true definition of
an acid is any
substance that forms
H+ ions in water.
The true definition of a
base is any substance
that forms OH- ions in
water.
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An example of a
neutral solution is:
Pure water
An example of an
acidic solution is: HCl
An example of a basic
solution is: NaOH
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Acid + Base =
neutralization
How does antacid
with a pH of 10 soothe
an upset stomach?
The antacid is basic and
when mixed with the
acid it causes
neutralization
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A buffer solution is an
aqueous solution
consisting of a mixture
of a weak acid and its
conjugate base (or vice
versa).
The buffer changes
very little and is used
as a means of keeping
pH at a nearly stable
value.
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An example of a buffer
solution is water
because many life
forms only thrive in a
relatively small pH
range.