Molecular Compounds. Types of Compounds Ionic Metal (or NH 4 + ) with a non-metal Transfer of...
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Transcript of Molecular Compounds. Types of Compounds Ionic Metal (or NH 4 + ) with a non-metal Transfer of...
Molecular Compounds
Types of Compounds
Ionic
• Metal (or NH4+) with a
non-metal• Transfer of electrons from
metal non-metal• Have ionic bonds
Molecular
• Non-metals only• Sharing of electrons
between non-metals• Have covalent bonds
Properties
Ionic
• Solid (s)• High melting points• When dissolved in water,
aqueous (aq), ionic compounds are electrolytes (good conductors of electricity)
• Electrolytes when melted.
Molecular
• Solid (s), liquid (l) or gas(g)
• Lower melting points• When dissolved in water,
(aq) or melted they are not electolytes
A molecular compound
• A molecular compound, is a pure substance that is formed from covalent bonds between nonmetals.
• Examples include:
• Water H2O (l)
• Carbon Dioxide CO2 (g)
• Oxygen O2(g)
Covalent Bonding• A covalent bond is a form of chemical bonding that is
characterized by the sharing sharing of pairs of electrons between atoms. This sharing allows the atoms to form a stable electron arrangement.
• For H2(g) that stable arrangement has 2 e-’s• For other molecular compounds an octet is required by
sharing.
Diatomic Molecules• A diatomic molecule is a
molecule consisting of only two atoms, of either the same or different chemical elements.
• http://www.dnatube.com/video/1290/Covalent-bond
O2 Oxygen
N2 Nitrogen gas
Diatomic Molecules
Here are some examples of diatomic molecules (same element):
hydrogen (H2)nitrogen (N2)oxygen (O2)fluorine (F2)chlorine (Cl2)bromine (Br2)iodine (I2)
Here are some examples of diatomic molecules (different elements):
CO – Carbon MonoxideCO – Carbon Monoxide
NO – Nitrogen NO – Nitrogen MonoxideMonoxide
HF – Hydrogen HF – Hydrogen FluorideFluoride
HCl – Hydrogen HCl – Hydrogen ChlorideChloride
HBrHBr – – Hydrogen BromideHydrogen Bromide
NN22O- dinitrogen O- dinitrogen monoxidemonoxide
SOSO33- sulfur trioxide- sulfur trioxide
Diatomic Elements
• I Bring Clay For Our New Home
• *to help you remember the molecular diatomic elements.
Diatomic Compounds• Since many combinations of some atoms are
possible, the number of atoms in the molecule is often stated using Latin prefixes.
– Carbon monoxide is CO while carbon dioxide is CO2.
– Memorize the prefixes!
Common Prefixesone mono six hexa
two di seven hepta
three tri eight octa
four tetra nine nona
five penta ten deca
• NBr3 = Nitrogen tribromide
• Dihydrogen dioxide = H2O2
Rules
• Use the Greek prefixes to indicate how many of each element are present in the formula. Mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca,…
• Drop mono for the first element.• Drop all prefixes if the first element is hydrogen.• Drop the second o in mono prior to a vowel.• Drop the a in prefixes ending in a prior to a vowel.
Examples:
• N2S
• N2O3
• CO2(g)
• HCl• CO(g)
• N2O4
• Dinitrogen monosulfide• dinitrogen trioxide • carbon dioxide• hydrogen chloride• carbon monoxide• dinitrogen tetroxide
Naming Molecular Compounds
• Can be more complicated than ionic compounds.
• There are also “common” names that will need to be memorized, such as:
• Water (H2O)• Methane (CH4)• Hydrogen peroxide (H202)• Sucrose C12H22O11
• Page 204– #1 5
Writing Formulas for Molecular Compounds
• Method is similar to the one used for ionic compounds.
• The combining capacity of a nonmetal tells you how many covalent bonds are needed to form a stable molecule.
• To figure out an atoms combining capacity you need to see where it falls on the periodic table or know how many valence electrons it has.
Methane
CH4
Writing Molecular Compounds Step by Step
Carbon & Sulfur
• Step 1:– Write the symbols and combining capacities
• Step 2:– Use the crisscross rule & the combining
capacities to get the proper subscripts.
Writing Molecular Compounds Step by Step
Carbon & Sulfur
This formula becomes C2S4 reduced to CS2.