+ SBI4U BIOCHEMISTRY Ms. Manning Atoms, Bonding & Molecular Polarity.
Molecular Compounds. Molecular Compound atoms of non-metals combine and form a pure substance...
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Transcript of Molecular Compounds. Molecular Compound atoms of non-metals combine and form a pure substance...
Molecular Compounds
Molecular Compound• atoms of non-metals combine and form a pure
substance• example: nitrous oxide (N2O)
• the atoms are joined by covalent bonds• each bond shares a pair of electrons• bonded atoms form a MOLECULE
Covalent Bonds• connection where two atoms share a pair of
electrons• the electron pair belongs to both atoms• attraction of atoms holds them together
SMART Board Activity
Remembering Non-Metals
• non-metal valence shells are almost full• the spaces can attract other electrons• allows non-metals to get close to each other• the two nuclei form strong attractions for each
other’s electrons• but not strong enough• net effect – share the electrons
Molecular Elements• molecular elements are two or more atoms of the same
element• a molecule made of only two atoms is called a diatomic
molecule
Molecular Elements that Commonly Form Diatomic Molecules:
Element Formula
bromine Br2
chlorine Cl2
fluorine F2
hydrogen H2
iodine I2
nitrogen N2
oxygen O2
Other Diatomic Molecules• there can be other types of diatomic
molecules• some can share 2 pairs of electrons• e.g. O2
• other diatomic molecules can be made of two different elements
• e.g. hydrogen and fluoride HF
Properties of Molecular Compounds
• at room temperature they can be liquid, solid or gas
• generally soft solids• if dissolved in water, they do not conduct
electricity• have relatively low melting points• two non-metallic elements can combine in
different ways and form different compounds• e.g. hydrogen and oxygen:water = H2O hydrogen peroxide = H2O2
Naming Molecular Compounds• any molecular compound that contains two
elements and does not contain hydrogen uses Greek prefixes
• the prefix indicates how many atoms of each element are in the compound
• e.g. P2O5 is diphosphorus pentoxide
• di- means 2, pent- means 5
Number of Atoms Prefix1 mono-2 di-3 tri-4 tetra-5 penta-6 hexa-7 hepta-8 octa-9 nona-
10 deca-
Naming Rules1. Name the first element (e.g. nitrogen)2. Name the second element, using the suffix “-ide”
(e.g. oxide)3. add prefixes to indicate the number of each atom
(e.g. dinitrogen monoxide)
Note: mono is not used in first element; if it is required before oxide, the last “o” in prefix is dropped
e.g. N2O
Hydrogen
• hydrogen is unique• often does not follow same naming• has given names:
Name Formulawater H2O
hydrogen peroxide H2O2
ammonia NH3
methane CH4
hydrogen sulfide H2S