Atoms and Bonding Review

• Valence Electronshighest energy levelheld most looslynumber of valence electrons determines many

properties, especially how it bonds• Electron Dot diagram

Includes chemical symbol and number of valence electrons• Chemical Bond

Stability comes with 8 valence electronsAtoms typically react in a way that will make them stable

ex. Group 17 bonding with group 1chemical bond is the force of attractions that holds two

atoms together

• Periodic TableElements location can tell you how many valence electrons it

has and how reactive that element isAtomic number increases from left to rightFirst energy level holds 2 valence electronsAll other hold up to 8

• Inert Gases8 valence electrons (except Helium has 2) full energy level so

they are stable• Reactive Elements

Halogens - 7 valence electrons, need 1 more – highly reactiveAlkali Metals – 1 valence electron, want to get rid of it, highly

reactive

Ionic Bonds

• IonAn atom or group of atoms that has an electric

chargeLose an electron atom becomes positiveGain an electron atom becomes negative

• Polyatomic Ionsions made of more than one atom

• Ionic Bondsattractions between oppositely charged ions

(attraction between opposites – negative an positive)Takes or transfers electrons

• Chemical Formulachemical symbols and subscripts that show

the ratio of the elementswhen ionic compounds form, negative and

positive charges balance outsubscript – tells you how many atoms of

that element are in the compound• Naming Ionic Compounds

name of the positive ion comes first (usually the metal), followed by the negative ion

Properties of Ionic Compounds

• Hard• Brittle• Solid• High melting point – because bonds are so

strong• Melted or dissolved in water – conduct

electricityCrystal = orderly 3D arrangement

Covalent Bonds

• Bond forms when there is a sharing of electrons• Usually with nonmetals• Held together by the attraction of each atom’s

nucleus for the electrons• Molecule – neutral groups of atoms joined by

covalent bonds• Double and triple bonds – share 2 or 3 pairs of

electrons

Covalent Bond Properties• Lower melting and boiling point – bond is not as strong• Do not conduct electric current when melted or dissolved• Unequal sharing of electrons cause slight electric charge• Polar bond – electrons NOT shared equally• Nonpolar bond – electrons shared equally• Depending how the atoms arranged will determine if

polar or not ex. Water H are on one side of O – O pulls in one direction

Carbon Dioxide C is in middle, O’s are on opposite sides pulling away from C therefore the overall pull is neutral

Metallic Bonds

• Alloy – mixture of 2 or more elements where at least 1 is a metal. They are stronger and less reactive than pure metals

• Metal atoms combine in regular patterns where the valence electrons are free to move from atom to atom

• Sea of electrons explains properties of metallic bonding

Properties of Metallic Bonding

• Malleable – pound into shapes• Ductility – draw into long wires• Luster – ability to shine• High electrical conductivity• High thermal conductivity