 Define these words  Ion  Ionic bond  Ionic compound  Chemical formula  Subscript  Covalent bond

 Define these words  Molecule  Double bond  Triple bond  Molecular compound  Nonpolar bond  Polar bond

 What is an ionic compound?  How does a positive ion form?  How does a negative ion form?

How elements bond

 Ion- is an atom or group of atoms that has an electric charge  When a neutral atom loses a valence electron, it loses a negative charge. It become a positive ion.  When a neutral atom gains an electron it gains a negative charge. It becomes a negative ion.

 Ionic Bond – the attraction between two oppositely charged ions  Result?  Ionic compound – the total number of positive charge ions equals the total number of negatively charged ions

 Polyatomic ion – means “many atoms”, ions that are made up of more than 1 atom

 Ionic compounds are  Hard, brittle crystals that have high melting points  conduct electric current when dissolved in water or melted  Ionic bonds usually form when a metal combines with a nonmetal

 A compound is a pure substance containing two or more elements that are chemically bonded.  Ex: The compound sodium chloride, or table salt, is formed

Chemical formula – group of symbols that shows the ratio of elements in a compound ex: magnesium chloride MgCl 2 Subscripts- tells the ratio of elements in a compound Ex: MgCl 2 when writing a formula: Write the symbol of the positive ion and then the symbol for of the negative ion Then add the subscripts that are needed to balance the charges Subscript

 Covalent Bond – the chemical bond that forms between nonmetal atoms when they share electrons  Some atoms are unlikely to lose or gain electrons because the number of electrons in their outer levels makes this difficult.  So what do they do?  SHARE

 Shared electrons  They move back and forth between the outer energy levels of each atom in the covalent bond.  So, each atom has a stable outer energy level some of the time.  The neutral particle is formed when atoms share electrons is called a molecule  Joined together by a covalent bond  A molecule is the basic unit of a molecular compound

 You can see how molecules form by sharing electrons

 Single bond  When 2 atoms share 1 electron  Double bond  When 2 atoms share 2 pairs of electrons  Triple bond  When 2 atoms share 3 pairs of electrons

 Molecular compound – a compound made up of molecules  Properties  Poor conductor of electric current when dissolved in water  Lower melting points and boiling points  Forces between the molecules are much weaker- so less heat is added to a molecular solids to separate the molecules (compared to ionic)

 Unequal sharing of electrons causes covalently bonded atoms to have slight electric charge  So what happens?  Nonpolar bond- electrons are shared equally  Ex: hydrogen molecule H 2  Polar bond- electrons are shared unequally  Atom with a stronger pull  slight negative charge  Atom with a weaker pull  slight positive charge  Ex: hydrogen flouride HF

 Water H 2 0  Water is an example of an ionic or molecular compound  This type of bond forms when????  Properties of these compounds include????