Test Objectives: Bonding Basics
- Know the definition of a chemical bond
- Recognize that the driving force of all chemical bond formation is to achieve an octet (stable valence electron configuration just like the noble gases)
- Be able to explain why energy is absorbed when a bond is broken (endothermic ) & energy is released when a bond is formed (exothermic)
- compound product has less energy and is more stable than individual elements formed from
- energy needed to overcome bonding forces holding elements together in a chemical bond
- Be able to predict the bond type of a chemical substance from its chemical formula
Ionic Bonding:
- know composed of metal and non-metal ions
- know electrostatic attractions (attraction of oppositely charged ions) is force of attractionin ionic bond
- know ionic compounds form crystal lattice structures and be able to explain in general terms how these structures are arranged
- be able to explain the physical propertiesof ionic compounds (general referred to as ‘salts’):
- hard, brittle, high melting points, low vapor pressure, high Hf, high Hv, soluble in water, know why ionic compounds in solid crystal form will shatter if struck hard
- be able to explain why ionic compounds will not conduct electricity in the solid (crystalline) phase but will conduct electricity in the molten state or in aqueous solution
- be able to draw Lewis Dot structures for ions & ionic compounds
- be able to describe the 2 step process in ionic bond formation:
1. transfer of valence electrons:
- from metal atom to non-metal atom due to large difference in electronegativity values between metal and non-metal atoms
- results in formation of ions: (+) charged metal ion(s) called cations and (-) charged non-metal ion(s)called anions
- be able to draw Lewis dot structures to illustrate electron transfer
2. ionic bondforms due to the electrostatic attraction of oppositely charged ions
Covalent Bonding:
- know composed of non-metal elements only
- knowelectrostatic attractions between (+) charged nuclear protonsof one atom and (-) charged electrons of neighboring atoms is the force of attractionthat forms a covalent bond
- be able to discuss the properties of covalent substances
- soft, brittle, low melting & boiling points, low Hf, low Hv, non-conductors of both heat & electricity
- be able to draw Lewis Dot structures for covalent compounds
- know that the small difference in electronegativity values between non-metal atoms results in non-metal atoms sharing their valence electrons in single,double and triple covalent bonds
- know how many pairs of electrons are shared in each type covalent bond:
- single bond: one pair shared
- double bond: two pairs shared
- triple bond: three pairs shared
Metallic Bonding:
- know composed of same metal ions
- be able to explain what is meant by the term “sea of mobile electrons”
- freely flowing valence electrons moving from one overlapping valence shell to the next
- know thatelectrostatic attractions between metal atom valence electrons metal cations formed from overlapping valence shells of same metal atoms is the force of attraction that forms a metallic bond
- be able to discuss the physical properties of metals
- explain the properties of metals in terms of delocalized electrons
- know that the number of delocalized electrons determinesstrength & hardness of any metal
- be able to explain why metals are malleable & ductile when struck hardwhile ionic compounds will shatter