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PSC 4012. Ionic Phenomena: A study of an environmental problem. PSC 4012. Changes in matter can be: (Fig 3.1, page 3.4) Physical (appearance) Chemical (electrons in last shell) Nuclear (nucleus). PSC 4012. Physical changes: Superficial change Needs little amount of energy - PowerPoint PPT Presentation
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PSC 4012
Ionic Phenomena: A study of an environmental problem
PSC 4012
Changes in matter can be: (Fig 3.1, page 3.4) Physical (appearance) Chemical (electrons in last shell) Nuclear (nucleus)
PSC 4012
Physical changes:
Superficial change Needs little amount of energy DOES NOT change nature of
element or compound DOES NOT affect the properties
of element or compound Changes state of matter
PSC 4012
Physical changes:
PSC 4012
Nuclear changes:
Most profound change Needs much more energy Involves particles in nucleus! An element is changed into
another ALL involve emission of
radiation (which can be harmless, dangerous, or lethal)
PSC 4012Chemical changes (chemical reactions):
More profound change Needs more energy Involves electrons in last shell NEW SUBSTANCES are formed Evidences of chemical change:_change of color_gas release_formation of precipitate_change of temperature
PSC 4012Chemical changes:
Ionization: when an atom gains or loses one or more electrons, it turns into an ion.
• Thus ions become negatively charged when atoms gain electrons (A-, anion)
• Or positively charged when atoms lose electrons (M+ cation)
PSC 4012
Classification of matter (Fig. 5.1, p 5.5):
Mixtures SeparationMethods:
_Filtration_Decantation_Evaporation_Distillation
PSC 4012
Molecules:Specific combination of atoms (same or different elements) that are united by chemical bonds
Example:_H2O (Water)1 molecule of water contains2 elements (hydrogen and oxygen)Each element has H: 2 atoms, O: 1 atom
PSC 4010: Chapter 4
Molecules:
Practice ExercisePage 3.8, Ex. 3.4
PSC 4012
Compounds:Pure chemical substance whose molecules are made of one or more elements (e.g. Gold, Water, Sulfuric Acid)
Element: A substance made of only one type of atom. For example: Gold (Au)Binary compound: Compound made of two elements. For example: Water (H2O)Complex compound: Compound made of more than two elements. For example: Sulfuric Acid (H2SO4)
PSC 4010: Chapter 4
Compounds:
Practice ExercisePage 3.8, Ex. 3.5
PSC 4012
Chemical bonds:The force that keeps atoms united in chemical compounds.
There are three type of chemical bonds:_Ionic_Covalent_Polar covalent
PSC 4012
Ionic bonds:
Is the transfer of one or more electrons from one atom to another (usually from a metal to a nonmetal)
Metals (low electronegativity, tendency to lose electrons, form Cations, positively-charged ion)
Non-metal (high electronegativity, tendency to gain electrons, form Anions, negatively-charged ion)
Ionic Bond
Be + O Be 2+ O2- (BeO)
4P5N
8P8N
4P5N
8P8N
PSC 4012
Electronegativity:Measurement of the force of attraction exerted by an atoms on the electrons it shares with another atom.
Fig 3.15, page 3.45
Electronegativity difference between bonding atoms
Chemical bond
More than 1.7 Ionic
Between 1.7 and 0.4 Polar covalent
Less than 0.4 Covalent
PSC 4012Covalent bonds:
Is the sharing of one or more pair of electrons between two identical atoms (non metals).
F + F F2
9P10N
9P10N 9P
10N9P
10N
PSC 4012
Polar covalent bond:
Is the sharing of one or more pair of electrons between two different atoms (non metals).
The more electronegative atoms tend to have a stronger attraction for the electron pair (or pairs).
This difference of electronegativity causes a certain degree of polarity, and as a result, the more electronegative atom ends up carrying a slightly negative charge whereas the less electronegative atom ends up with a slightly positive charge.
Slightly charged means a fraction of the actual charge. Do not confuse with ionic bond where the transfer of electrons is complete and so is the charge of the ions or elements involved.
PSC 4012
Polar covalent bond (H2O)
8P8N1P
0N 1P0N
H (δ+) H (δ+)O(δ-)
PSC 4012
Ionic bond Covalent bond Polar covalent bond
Between a metal (cation) and non metal (anion)
Between two identical atoms(non-metals)
Between two different atoms (non-metals)
Transfer of one or more electrons from one atom to another
Sharing of one or more pair of electrons
Sharing of one or more pair of electrons
Results in opposite-charged ions. One positive: cation (metal)One negative: anion (non metal)
No charges
No polarity
Perfect sharing
Results in slightly charged atoms.Less electronegative slightly positiveMore electronegative, slightly negative
NaCl, CaO, Li2O, CaF2 H2, N2, F2, Cl2 NH3, CCl4, PF5, H2O