molecular compounds

Molecular CompoundsMolecular Compounds

Learning Goal:

• Students will be able to name, draw and determine the formula of compounds

Agenda:• Ionic Compound Quiz• Yesterday’s work – problems?• Molecular Compounds • Practice time…

• Ionic CompoundsIonic Compoundsmetal + non-metal compoundmetals lose electrons to non-metalsmade of ions of opposite charges

Polyatomic Compounds

• Polyatomic Ion: An ion formed by a group of atoms with a shared charge

• Found in lots of everyday • Substances

• Copy the chart from p.182

Polyatomic Compouds

• Naming:– Name of positive ion first and polyatomic ion

second• Formulas:

– Use the crisscross method as before– Treat the polyatomic ion as one unit– Keep the polyatomic ion in brackets if there is a

number behind it

• Covalent BondsCovalent Bondsa shared pair of electrons between two non-

metal atomsatoms share electrons to form a stable

arrangement (like the noble gases)It’s like tug of war for the electrons that no

atom wins thus they “Share”

Molecule: a particle in which atoms are joined by covalent bonds

ExampleExample

• Ammonia – NH3

Ionic vs CovalentIonic vs Covalent

• Diatomic MoleculeDiatomic Moleculemolecule made of two atomsexample: H2

Elements that Form Diatomic MoleculesElements that Form Diatomic Molecules

Name of Element FormulaHydrogen H2

Oxygen O2

Nitrogen N2

Fluorine F2

Chlorine Cl2Bromine Br2

Iodide I2

Where We Find Molecular Where We Find Molecular Compounds?Compounds?

• molecular compounds are all around us• molecular compounds are found in water,

sugar, and molecules that provide flavour and colourexample: can of pop

Combining CapacityCombining Capacity• Combining capacity is the number of

electrons an atom can gain, lose, or share to form a stable molecule.

• Example: Oxygen has a combining capacity of 2.

Writing Formulas for Molecular Writing Formulas for Molecular CompoundsCompounds

• Write the symbols with combining capacities (element farthest left first)

• Crisscross the combining capacities• Reduce subscripts if possible

Example: carbon & sulfur C4 S2

C2S4

CS2 – carbon disulfide

Naming Molecular CompoundsNaming Molecular Compounds

1) Some molecular compounds are named the same way as IONIC COMPOUNDS. Ex. H2S is Hydrogen Sulfide

Naming Molecular CompoundsNaming Molecular Compounds

2) Many molecular compounds have COMMON NAMES. (Know these) Water (H2O) Ozone (O3) Ammonia (NH3) Hydrogen peroxide (H2O2) Methane (CH4)

3) PREFIXES are another method used to name molecular compounds.Prefixes are used to count the number of

atoms present in the compound.If there is only one atom in the first element in

the molecular compound, the prefix “mono” is not used.

• Examples:Carbon monoxide – COCarbon dioxide – CO2

Prefixes in Molecular CompoundsPrefixes in Molecular CompoundsPrefix Number Example

Mon(o) 1 Carbon monoxide (CO)

Di 2 Carbon disulfide (CS2)

Tri 3 Sulfur trioxide (SO3)

Tetra 4 Carbon tetrafluoride (CF4)

Pent(a) 5 d

Hexa 6