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Bonding. A chemical bond is a force that holds atoms together.
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A chemical bond is a force that holds atoms together.
Two Types of Bonds 1. Ionic Bond – the attraction between two oppositely charged ions. An ionic bond is formed when atoms gain or lose electrons. Ionic bonds form compounds.
Ion – an atom or group of atoms that has become electrically charged. It is a charged particle.When an atom loses an electron, it loses a negative charge and becomes a positive ion.When an atom gains an electron, it gains a negative charge and becomes a negative ion.
Atoms that gain electrons have a negative valence. (charge)Atoms that lose electrons have a positive valence. (charge)
2. Covalent Bonding – A type of bonding in which electrons are shared.When covalent bonding occurs, molecules are formed.
Molecule – a particle made of 2 or more atoms covalently bonded together.Compound – two or more elements chemically combinedby gaining, losing, or sharingelectrons.
Chemical formulas – a shorthand way to represent a compound. ( H2O)In a chemical formula, the element with the positive charge is always written first.
Valence number – The number of electrons an atom needs to gain, lose, or share to become stable. (Gain electrons – negative valence)(Lose electrons – positive valence.)
Subscript – the number that shows how many atoms of an element are in the compound.
How to Write Formulas • 1. Write the symbol correctly for both elements. • 2. Write the valence number above each symbol. Make sure you have a positive first, and then a negative. • 3. Criss-cross valences to make a subscript. • 4. NEVER write 1 as a subscript. (It is understood to be 1 if there is no number.) • 5. Reduce to lowest terms.
Examples • Sodium Chloride Aluminum Oxide • Copper (I) Sulfide Iron (III) Iodide
Practice Problems • Aluminum Bromide • Calcium Iodide • Copper (I)Chloride • Hydrogen Oxide • Magnesium Nitride • Potassium Sulfide • Barium Fluoride • Lead Bromide
Calcium Sulfide 2. Copper (I)Iodide 3. Potassium Chloride 4. Iron(III) Bromide 5. Sodium Nitride 6. Antimony (V) Oxide
Binary Compound – a compound composed of 2 elements. Polyatomic Ion- a group of positively or negatively charged covalently bonded atoms.
Calcium Phosphate Tin (V) Chromate Ammonium Oxide Magnesium Sulfate
Naming compounds – change the ending of the second element to – “ide”.(Do not change the names of polyatomic ions.)Ex: NaCl - Sodium Chloride Ba3N2 – Barium nitride Fe2O3 – Iron (III)Oxide