Unit 6: Molecules & Compounds
Key Terms
Ionic Bonding
Electron dot diagram
ion
anion
cation
chemical bond
ionic bond
chemical formula
crystals
Covalent Bonding
Naming Compounds & Writing Formulas
Covalent bond
Polyatomic ion
molecule
polar covalent bond
Essential Questions
Electron Configurations: electron dot diagram – a model of an atom in which each dot
represents a valence electron.

What is a chemical bond?
A chemical bond is the force that holds atoms and ions together as a unit.

How is an ionic bond different from a covalent bond?
Ionic Bonds: some elements achieve stable electron configurations through the transfer of
electrons between atoms.
Formation of ions – when an atom gains or losses an electron, the number of protons in no
longer equal to the number of electrons. The charge is no longer neutral.
ion – an atom with a net positive or negative charge. Represented by a + or – sign.
Cl gains an electron 17 protons
18 electrons charge of 1- Cl1- or Clanion – (an eye un) an ion with a negative charge
Naming: using part of the element name plus the suffix –ide.
Cl- : Chloride ion.
Na loses an electron 11 protons
10 electrons charge of 1+ Na1+ or Na+
cation – (kat eye un) an ion with a positive charge
Naming: just use the elements name.
Na+ : Sodium ion.
ionic bond – the force that holds cations and anions together. It forms when electrons are
transferred from one atom to another.
Covalent bond – a chemical bond in which two atoms share a pair of valence electrons.
single bond – when 2 atoms share one paid of electrons.
molecule – a neutral group of atoms that are joined together by one or more covalent
bonds.
- The hydrogen molecule is neutral because it has 2 electrons and 2 protons
(one from each)
Difference between Ionic and covalent:
ionic: gain or lose an electron (+/- charge)
covalent: share an electron (Neutral charge)
multiple bonds – N2 : each atom of nitrogen shares 3 pairs of electrons, each atom
will have 8 valence electrons. N≡N
- in general, elements on the right of the periodic table have a greater attraction
for electrons than the left have (except for noble).
- in general, the elements at the top of a group have a greater attraction for
electrons than elements at the bottom of the groups.
-which element has the strongest attraction for electrons? Fluorine (most
reactive nonmetal)

Identify elements in a compound from its formula.
Use sample equations

What information do you need to consider in order to write the correct formula for a
compound?
- which elements are in the compound
- the number of valence electrons

Identify a correct formula given elements from the periodic table.
Give a list of samples:
NAMING BINARY COMPOUNDS
1. Metal
+
nonmetal
cation = name of element
anion = part of name with suffix –ide
2. Transition +
Transition
use Roman Numerals
3. Nonmetal +
Nonmetal
use Prefixes

What is the rule used for naming a binary compound composed of a metal bonded to a
nonmetal? (Use suffix –ide)
Cation = name od element
Anion = part of name of element with suffix -ide
Common Anions
Element
Fluorine
Chlorine
Bromine
Iodine
Oxygen
Sulfur
Nitrogen
Phosphorus
Ion
Fluoride
Chloride
Bromide
Iodide
Oxide
Sulfide
Nitride
Phosphide
Symbol
FClBrIO2S2N3P3-
Charge
11112233-
- binary compound – a compound from only two elements.

What is the rule used for naming binary compounds composed of transition metals bonded to
nonmetals? (use roman numberals)
- many transition metals form more than one type of ion.
- When a metal forms more than one ion, the name of the ion contains a Roman
numeral to indicate the charge on the ion.
EX: red copper(I) oxide :
“copper one oxide”
two Cu1+ ions to balance O2Cu2O
black copper(II) oxide :
“copper two oxide”
one Cu2+ ion to balance O2CuO
Some Metal Cations
Ion Name
symbol
Copper(I)
Cu+
Copper(II)
Cu2+
Iron (II)
Fe2+
Iron(III)
Fe3+
Lead(II)
Pb3+
Lead(IV)
Pb4+
Ion Name
Chromium(II)
Chromium(III)
Titanium(II)
Titanium(III)
Titanium(IV)
Mercury(II)
Symbol
Cr2+
Cr3+
Ti2+
Ti3+
Ti4+
Hg2+
What is the rule used for naming binary compounds composed of nonmetals bonded to other
nonmetals? (use prefixes)
- write the symbol of the elements in the order the elements appear in the name.
- prefix : indicates number of atoms of each element in the molecule. (subscript)
- no prefix = only one.
EX:
diphosphorus tetraflourine ? P2F4
hydrogen dioxide: HO2
dihydrogen oxide: H2O

Correctly match simple binary compound names to their formulas.
worksheet