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????