Compounds: Elements in combinations and Acids Bases and salt

• COMPOUND

  • A substance composed of atoms of two or more elements chemically combined in fixed proportions.
  • They are represented with symbols known as chemically combined formulae.
• CHEMICAL FORMULA

  • Shows the elemental parts or components of a compound.
• Types of chemical formula

  A) Chemical Formula

  B) Chemical Formula

  C) Empirical Formula

  D) Molecular formula

  E) Condensed Formula

  F) Structural Formula

  
• Structures

  • The number written on the lower right side of the symbol of the element is called the subscript.
  • The SUBSCRIPT tells the number of atoms of each element in a compound.
  • An ATOM is the smallest particle present in an element.
• • Compounds are either COVALENT or IONIC COMPOUNDS
• IONIC COMPOUND

  • The positive or negative ions are held together by electrostatic forces of attraction
• • Ionic compound (ex. Sodium chloride, NaCI) are defined as being compounds where two or more ions are held together next to each other by electrostatic force of attraction.
• • The electrostatic force is an attractive and repulsive force between particles are caused due to their electric charges.
• • The formation of an ionic bond is the result of the transfer of one or more electrons from a metal into a non-metal.
• CATIONS - Positive charged ions formed when metals lose electrons during chemical reactions.
• ANIONS - Negative charged ions formed when non-metals gain electrons during chemical reactions.
• COVALENT

  • The smallest units are discrete, individual molecule

   
• • A covalent compound (ex. Carbon dioxide, CO2 ) is a compound in which the atoms that are bonded share electrons rather than transfer electrons from one another.

   
• In a covalent bond, two atoms share pairs of electrons.
• • Covalent Bond/Bonded share electrons - is a chemical bond that involves the sharing of electrons to form electron pairs between atoms  
• The structures

  A) Elements

  B) Compounds

  C) Title

  
• Acids - are substances which ionize to produce hydrogen ion (H plus).
• • Compounds can also be classified into acids, bases and salts.
• Bases - are substances which ionize to produced hydroxide ions in water.
• Neutralisation Reaction - is a type of chemical reaction whereby an acid reacts with a base to form a salt and water.
• Salts - Are crystalline compounds formed by the reaction of an acid and a base.