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#1 17-02-2020 07:25:49

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Balanced chemical equations, Law of conservation of matter (mass)

A chemical reaction can be represented by "Chemical equation", Chemical equation is a set of symbols and chemical formulas representing the reactants and products' molecules in the chemical reaction and it represents the conditions of the reaction as well.

Law of conservation of matter (mass) & Law of constant ratios


The word equation and symbolic equation expressing the reaction of magnesium with oxygen. The chemical equation must be balanced that means: the number of atoms of each element in the reactants must equal the number of atoms of the same element in products. The mass of magnesium is increased when it is burned because it combines with oxygen forming magnesium oxide.

2Mg + O2 → 2MgO

Properties of Acids, Bases (alkalis), Oxides and Salts


All acids turn colour of litmus into red and having a sour taste, while all bases turn the colour of litmus into blue with a bitter taste because acids, when dissolved in water, produce positive hydrogen ions H+ which responsible for their properties, while bases, when dissolved in water, produce negative hydroxide ions (OH)− which responsible for their properties.

Acids are substances (materials) which dissociate in water producing positive hydrogen ions H+, Bases are substances that dissociate in water producing negative hydroxide ions (OH)−, Caustic soda is from bases, while lead bromide is from salts because caustic soda contains negative hydroxide ion, while lead bromide is formed from the combination of a positive metal ion with negative nonmetal ion.

Valency is the number of electrons that an atom gains, loses or even shares during a chemical reaction, The valency of noble gases is zero because their outermost energy level is completely filled with electrons [ have 8 electrons except (He) has 2 electrons], The valency of an element is determined according to the number of electrons in the outermost energy level of its atom.

What is valency?


Sodium (11Na) is monovalent (1) because it loses one electron during the chemical reaction, Chlorine (17Cl) is monovalent (1) because it gains or shares with one electron during the chemical reaction.

Oxygen (8O) is divalent (2) because it gains or shares with two electrons during the chemical reaction, Magnesium (12Mg) is divalent (2) because it loses two electrons during the chemical reaction.

Aluminium (13Al) is trivalent (3) because it loses three electrons during the chemical reaction, Argon (18Ar) is zero because it doesn't lose, gain or share with any electrons due to the completeness of their outermost energy levels with electrons.

What is meant by the chemical formula of sodium chloride molecule is (NaCl), this means that the molecule of (NaCl) consists of one atom of sodium element (Na) and one atom of chlorine element (Cl).

The ionic bond is a kind of a chemical bond that is formed as a result of a combination of a positive ion for an atom of a metallic element and a negative ion for an atom of a nonmetallic element to form a molecule of an ionic compound, Ionic bond produces compounds molecules only and doesn't produce elements molecules because the ionic bond arises between two different atoms.


Ionic bonds & covalent bonds


The covalent bond is a type of chemical bond that occurs between two nonmetal atoms to form a molecule of a covalent compound, The covalent bond produces elements molecules because it arises between two atoms for one nonmetallic element, The covalent bond produces compounds molecules because it arises between two atoms for two different nonmetallic elements.


Both sodium ion and oxygen ion have the same number of electrons because sodium ion is formed when sodium atom loses one electron and changes into (Na+) which contains 10 electrons, while oxygen ion is formed when oxygen atom gains two electrons and changes into (O−2) which contains 10 electrons too.

Properties of Metals, Nonmetals & Noble gases


Metals are the elements that contain less than 4 electrons (1 or 2 or 3 electrons) in the outermost energy level, metals are solids except mercury (Hg) which is the only liquid metallic element, Metals have a metallic luster, metals are good conductors of heat and electricity, metals are malleable and ductile.

Inert gases don't participate in chemical reactions under the ordinary conditions due to the completeness of their outermost energy levels with electrons, The number of electrons of the ion differs from that of its atom because the number of the electrons in the ion is less than or more than its number in the same atom by the number of lost or gained electrons.

Noble gases don't participate in chemical reactions under ordinary conditions due to the completeness of their outermost energy levels with electrons.

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