Outline
Basic Chemistry
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Chemical Elements
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Chapter 2
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Chemical Bonding
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Atoms
Isotopes
Molecules and Compounds
Ionic and Covalent
Hydrogen
Properties of Water
Acids and Bases
Chemical Elements
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Matter refers to anything that has mass and
takes up space.
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Atoms
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92 naturally occurring elements.
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Atoms are the smallest unit of matter.
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Only six make up 98% body weight of organisms.
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Elements grouped in periodic table based on
individual characteristics.
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Vertical columns are groups.
Horizontal
o o a rows
o are
a periods.
p od
Protons and neutrons found in nucleus.
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CHNOPS
„ Carbon
„ Hydrogen
„ Nitrogen
„ Oxygen
„ Phosphorus
„ Sulfer
Electrons orbit nucleus.
Mass number equals sum of protons and neutrons.
„ Atomic number refers to number of protons.
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Periodic Table
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Atomic symbol represents each element.
Isotopes
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Isotopes are atoms of the same element
with a differing number of neutrons.
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Therefore some atoms of the same element
will
ill weigh
i h different
diff
amounts.
H 1 no neutron
H 2 1 neutron
Total population determines weight H= 1.007
thus most H is H 1
1
Electrons
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Electron Orbitals
In an electrically neutral atom, positive
charges of protons are balanced by the
negative
g
charges
g of electrons.
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Orbital is the volume of space where an
electron is most likely to be found.
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Electrons are attracted to the nucleus, and thus
energy is required to push electrons into higher
orbits.
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Orbitals
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Li=1s22s1
Be=1s22s2
B= 1s22s22p1
C=1s22s22p2
N=1s22s22p3
O=1s22s22p4
F=1s22s22p5
Ne=1s22s22p6
Notice the pattern?
Total the superscripts ad you get the atomic number
Elements and Compounds
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Molecule - Two or more atoms bonded
together.
Compound - Two or more different types
of atoms bonded together.
Ionic Bonding
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Ionic bonds are formed when electrons
are stolen from one atom to another.
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Electron transfer causes a charge imbalance
in each atom.
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Ions
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Electron orbitals are the position of the
electron in relation to the energy that it uses.
We will look at s and p orbitals
S orbitals
bit l hold
h ld 2 electrons
l t
P orbitals hold 6 electrons
H =1 s1
He=1s2 This element has a full shell and is
happy
Notice all elements in column 18 are happy
Sodium Chloride
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Na=1s22s22p63s1
Na+ =1s22s22p6 Missing an electron
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Sodium Chloride
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thus + charged
Cl = 1s22s22p63s23p5
Cl--=1s22s22p63s3p6 Gained an electron
Cl
thus – charged
These combine to form a matrix due to charges
Table salt
2
Covalent Bonding
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Covalently Bonded Molecules
Covalent bonds are formed when two
atoms share electrons so that each atom
has a complete
p
outer shell.
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Molecule Shapes
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Molecules have threethree-dimensional shapes.
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Models
„ Ball and stick
„ Space
Space--filling
Covalent Bonding
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Nonpolar covalent bonds are formed when
sharing of electrons between atoms is
equal.
q
Polar covalent bonds are formed due to
unequal sharing of electrons between
atoms.
Electronegativity
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Hydrogen Bonding
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A hydrogen bond is formed when polarity
within a water molecule causes the
hydrogen
y g atoms in one molecule to be
attracted to the oxygen atoms in the other
water molecules.
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Weak and easily broken.
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Electronegativity is the attraction of an
atom for the electrons in a covalent bond
Most electronegative is F
Charge gradient
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Many together can be quite strong.
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On one extreme is stealing on the other is
sharing or
On one extreme is ionic on the other is
covalent bonding
H bonding is in the middle
Ionic Æ Polar Æ H Æ Nonpolar Æ true
covalent
Electronegativity Æ
3
Water Molecule
Properties of Water
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High Heat Capacity
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Large number of hydrogen bonds absorb heat
without a large
g change
g in temperature.
p
High Heat of Vaporization
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Large number of hydrogen bonds must be
broken to evaporate water.
Properties of Water
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Solvent
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Hydrophilic - Attracts water.
Hydrophobic - Cannot attract water.
A solution contains dissolved solutes
solutes..
Frozen water less dense than liquid water.
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Ice acts as an insulator on top of a frozen
bodyy of water.
Melting ice draws heat from the environment.
Cohesive and Adhesive
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Properties of Water
Water can be drawn up a tubular vessel.
High Surface Tension
Acids and Bases
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Acids are substances that dissociate in
water and release hydrogen ions (H+).
Bases are substances that either take up
hydrogen ions (H+) or release hydroxide
ions (OH-).
pH Scale
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pH scale used to indicate acidity and
basicity of a solution.
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Ranges from 00-14
7 = Neutral
>7 = Base
„ <7 = Acid
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Logarithmic Scale
4
Acid or Base
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H++ ClCl- Æ HCl
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K+ + OH- Æ KOH
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acid since H+
base since OHOH-
Na+ + ClCl- Æ Na+ Cl
Cl-„
Salt since no hydronium nor hydroxide
Review
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Chemical Elements
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Chemical Bonding
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Atoms
Isotopes
Molecules and Compounds
Ionic and Covalent
Hydrogen
Properties of Water
Acids and Bases
5