chemical compounds lesson-2 unit-1 made by: dr. niveen fawzy
TRANSCRIPT
Chemical compounds lesson-2 unit-1
Made by:
Dr. Niveen Fawzy
The valency• During chemical reactions atoms try to reach
the stable state by:
-Loosing their outermost electrons (in case of metals)
-Gaining a no. of electrons to complete the outer shell by (8) electrons (in case of non-metals)
-Sharing a no. of electrons with other atoms (in case of non-metals)
• The valency:• It’s the no. of electrons that an atom gains or loses or
shares during a chemical reaction• N.B: The outermost electrons of an atom determines
its valency
Some metals & their valencies Metal Valency Metal Valency Metal Valency
Lithium (Li) Monovalent Calcium (Ca) Divalent Aluminum (Al) Trivalent
Potassium (K) Monovalent Magnesium (Mg)
Divalent Gold ( Au) Trivalent
Sodium (Na) Monovalent Iron II (Fe) Divalent Iron III ( Fe) Trivalent
Silver (Ag) Monovalent Lead ( Pb) Divalent
Copper I (Cu) Monovalent Copper II (Cu)
Divalent
Mercury (Hg) Divalent
Some metallic elements have more than one valency such as:Copper I Monovalent Copper II Divalent Iron I Monovalent Iron II Divalent
• Some non-metals & their valencies:
Non-metals Valency Non-metal valency
Hydrogen (H) Monovalent Sulphur (S) Tetravalent
Chlorine (Cl) Monovalent Carbon (C) Tetravalent
Fluorine (F) Monovalent Nitrogen (N) Pentavalent
Bromine (Br) Monovalent Phosphorus (P) Pentavalent
Iodine (I) Monovalent Sulphur (S) Hexavalent
Sulphur (S) Divalent
Oxygen (O) Divalent
Nitrogen (N) Trivalent
Phosphorus (P) Trivalent
Give reason:
Atomic group (Radical) • Its properties: It’s a set of atoms of different
elements joined together , behave like one atom during a chemical reaction , having its own valency & doesn’t exist solely
Chemical formula• It’s a formula that represents the number & types of
atoms in a molecule • Steps to write a chemical formula for a compound:
Write the chemical formula of:
Write the chemical formula of the following & no. of elements & no. of atoms of each
• 1- Aluminum carbonate
• 2- Copper carbonate
• 3- Sodium nitrate
• 4- Calcium sulphate
5- Hydrogen chloride
Types of compounds• Compounds can be classified acc. to their properties into:
1- Acids 2- Bases 3 -Oxides 4- Salts
First: Acids & Bases (alkalis)
Notice that:
Classification of acids• Acids are classified acc. to their strength(degree of
Ionization):
Stable acids Unstable acids
Sulphuric acid is the most stable acid due to its high boiling point
Carbonic acid
Acids are classified acc. To their stability (Bp & difficulty of its decomposition):
• Warning: • Never touch acids or bases with bare hands as they
have corrosive effect on skin• Sodium hydroxide is also called (caustic soda) • Calcium hydroxide is also called (lime water)
• If we have 2 test tubes , one containing acid & the other base we can distinguish them by using litmus paper
Oxides & its classification• They are compounds resulted from combination
between oxygen& an element (metal & non-metal)
Salts• They are compounds resulted from the combination of a
positive ion or ( positive atomic group) with a negative atomic group or ( a negative non-metal ion except oxygen)
• Formation of salts
Classification of mineral salts
NB.-Salts exists in earth crust or is dissolved in water-They are variant in taste ,color ,smell , solubility in water
Model answers of book pages 25,26
• Question (2):
• (A):
• Answer in slide no. 11
• (B): Give reason: • 1- Because acids produce positive hydrogen ions ,
while bases produce negative hydroxide ions
• 2- Because during chemical reactions potassium atom loses one electron , while oxygen atom gains or shares with 2 electrons
• 3- Because oxygen is divalent , while sodium is monovalent