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Ionic/Covalent/Metallic Bonding Notes. Stable or Unstable?. An atom is only stable if it has a full valence shell If an atom is stable, it will not bond If an atom is not full, it will bond. Compounds. Compounds are formed when 2 atoms of different elements bond together.
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Stable or Unstable? • An atom is only stable if it has a fullvalenceshell • If an atom is stable, it will notbond • If an atom is not full, it will bond
Compounds • Compounds are formed when 2 atoms of differentelements bond together. • Atoms bond to fill their valence shell • An atom will bond with an many atoms as it takes to fill its outer shell • Once the valence shell is full, that atom is stable
ION – any atom with more or less electrons than it is supposed to have* *Remember that the number of electrons is supposed to be equal to the number of Protons if the atom has a neutral charge
Types of Chemical Bonds • There are 3 types of chemical bonds: • Ionic Bonds • Covalent Bonds • Metallic Bonds
Ionic Bonds • Ionic bonds exist between a metal and a nonmetal • When two atoms bond ionically, they gain/lose electrons. Electrons are transferred from one atom to another. • When an atom gains or loses an electron, it becomes an ion
Ions +2 Ca It has 2 valence electrons. How many does it need to be stable? 8…so it can either lose 2 or gain 6. Which is easier? Calcium is in group 2. How many valence electrons does it have? Which other elements would lose 2 electrons? Losing 2…if it loses 2 electrons, it becomes positive +2 +2 +2 +2 +2 +2
Ions +1 0 +1 +2 +3 +4 -3 -2 -1 0 +1 -2 +2 +3 +4 -3 -1 0 +1 -2 +2 +3 +4 -3 -1 0 +1 +2 -2 -3 +3 +4 -1 0 +1 +2 +4 -3 -2 -1 0 +3 +1 +2
Ionic Bonds • Properties of Ionic Compounds • High melting point • Good conductor of electricity • Solid at room temperature
Covalent Bonds • Covalent bonds exist between NONMETAL and NONMETAL. • Example: H2, H2O, NO3, CH4 • Covalent bonds SHARE electrons. • Shared electrons don’t belong to either atom.
Covalent Bonds • Properties of Covalent Compounds • Low melting point • Poor conductor of electricity • Liquid or Gas at room temperature
METALLIC BONDbond found in metals; holds metal atoms together very strongly
Metallic Bond • Formed between atoms of metallic elements • Electron cloud around atoms • Good conductors at all states, lustrous, very high melting points • Examples; Na, Fe, Al, Au, Co
Lewis Structures of molecules Single Bond: Two atoms sharing one electron pair. Example: H2 Double Bond: Two atoms sharing two pairs of electrons. Example: O2 Triple Bond: Two atoms sharing three pairs of electrons. Example: N2 Resonance Structures: More than one Lewis Structure can be drawn for a molecule. Example: O3
Carbon dioxide, CO2 Total Number of valence electrons = 4 + (2 x 6) = 16 Double bonds • Rules for Drawing Lewis Structures • First sum the number of valence electrons from each atom • The central atom is usually written first in the formula • Complete the octets of atoms bonded to the central atom (remember that H can only have two electrons) • Place any left over electrons on the central atom, even if doing so it results in more than an octet • If there are not enough electrons to give the central atom an octet , try multiple bonds E.x. 1. PCl3 Total Number of valence electrons = 5 + (3 x 7) = 26
1. Odd Number of Electrons NO Number of valence electrons = 11 Resonance occurs when more than one valid Lewis structure can be written for a particular molecule (i.e. rearrange electrons) NO2 Number of valence electrons = 17 Molecules and atoms which are neutral (contain no formal charge) and with an unpaired electron are called Radicals O2
