What Kind of Bonds Hold Elements Together?

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Transcript What Kind of Bonds Hold Elements Together?

How Do We Make
Compounds?
What is inside the atom?

Atom: made of subatomic particles
Proton (+) = atomic # : determines the
identity of the element
 Neutron (no charge)
 Electron (-)

Atomic mass = protons + neutrons
 Periodic Table : arranged by Russian
Chemist Dmitri Mendeleev, by atomic #

Why do atoms bond?
Octet Rule: Every atom wants 8 electrons to fill
the valence shell (outer most shell)
 Ion: Charged atom (Ca+2)
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Cation: + charged ion
 Anion: - charged ion
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Polyatomic Ion: Two or more atoms covalently
bonded together to form an ion (SO4-2)
What are Ionic, Covalent and
Metallic Bonds?
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Ionic Bond: An electron is
transferred from one
element to another
(metal to nonmetal)
Covalent Bond: Electrons
are shared (nonmetal to
nonmetal)
Metallic Bond: Sea of
electrons (Metal to
Metal)
Molecules and Molecular
Compounds
 Properties
of molecular compounds
 Low melting and boiling points
 Usually gas or liquid
 Composed of two or more
nonmetals
 O2, O3, H2O
How Do We Name Molecular
(covalent) Molecules?
Name the first element
 Keep the root of the 2nd
element, drop the
ending & add “ide”
 Now add the prefixes
 The first element does
not need the prefix
mono
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Prefixes:

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Mono (1)
Di (2)
Tri (3)
Tetra (4)
Penta (5)
Hexa (6)
Hepta (7)
Octa (8)
Nano (9)
Deca (10)
Name CO2
 Name CCl4
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Let’s Compare!
How Do We Name Ionic
Compounds?

Name the first element. Use the root of 2nd element and
add “ide” (no prefixes)
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If there is a transition metal, determine the charge and
add Roman Numerals

If there is a polyatomic ion, name the first element and
name the polyatomic ion.

Name: CaCl2, FeO, NaOH
Exceptions:
 Some
of the transition metals have
only one ionic charge:
 Do not use roman numerals for
these:
 Silver is always 1+ (Ag1+)
 Cadmium and Zinc are always 2+
(Cd2+ and Zn2+)
What are Oxidation Numbers?
How do we draw a Lewis
Dot Diagram?
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Determine the number of valence electrons
Write the chemical symbol
Place a dot for each valence electron around the
symbol
Writing Chemical Formulas
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Rules of writing formulas:
positive ion (cation) is written first …
this is usually a metal
 negative ion (anion) is written second …
this is usually a nonmetal
 subscripts are used to show how many
ions of each part are in the compound.
They are used to balance the charge of
the ions.
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Using the Criss Cross
Method
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Determine the oxidation number (charge) on each ion.
Write the chemical symbols of each ion
(cation1st,anion 2nd)
Cross over the numbers ignoring the charges
Reduce if necessary
HOW DO WE NAME BASES?

BASES: USE SAME RULES
AS NAMING COMPOUNDS

EXAMPLE:
NaOH
SODIUM HYDROXIDE
NOW YOU TRY:
 Ca(OH)2
 KOH
 Mg(OH)2
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CALCIUM
HYDROXIDE
POTASSIUM
HYDROXIDE
MAGNESIUM
HYDROXIDE
HOW DO WE NAME ACIDS?
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ACIDS: AN ACID’S NAME COMES FROM THE ANION IT PRODUCES WHEN IT
DISSOCIATES. HERE ARE SOME RULES;
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IF THE ANION ENDS IN “IDE” CHANGE IT TO “IC” AND ADD THE WORD
“HYDRO” IN FRONT;
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HYDROGEN CHLORIDE
HYDROCHLORIC ACID
IF THE ANION ENDS IN “ATE”, CHANGE IT TO “IC” AND DO NOT ADD A
PREFIX
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HCl
H2SO4 HYDROGEN SULFATE
SULFURIC ACID
IF THE NAME ENDS IN “ITE”, CHANGE IT TO “OUS” AND DO NOT ADD A
PREFIx
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H2SO3 HYDROGEN SULFITE
SULFUROUS ACID