IONS
Simple Ion Review – Holt
Section 1.
KEY TERMS
Octet Rule – The assumption that atoms are most stable with an outer
valence shell of 8 electrons
Ion – a charged atom formed when an atom gains or loses electrons
Cation – An ion with a positive charge
Anion – An ion with a negative charge
CHEMICAL REACTIVITY
An element’s reactivity depends on the amount and orientation of valence
electrons.
The fewer electrons an atoms needs to gain or lose, the more reactive.
O example: 2 electrons needed for a stable octet and is
reactive than carbon who needs 4.
more
VIDEO EXAMPLES
Sodium and Water
Chlorine and Sodium
Magnesium and Oxygen
REACTIVE ELEMENTS
Noble gases have the most stable configuration. Notice this level has
8 valence electrons, making it most stable.
In chemical reactions atoms gain/lose electrons to have the same
electron configurations to the stable noble gases.
Alkali Metals and Halogens are most reactive (see periodic table)
because they have the least electrons to lose/gain to form a stable
octet.
TYPES OF IONS
Atoms who become an ion with a Positive Charge are called a
cation.They lose electrons from their outermost energy levels to
become positively charged. Metals tend to form cations.
An ion with a with a negative charge is called an anion. Anions gain
electrons to become more negatively charged. Nonmetals tend to
form anions.
TYPICAL IONS
Atom
# Protons
# Electrons
Charge
(#protons #electrons)
Cation/Anion/Neutral
Li
3
2
Cation
F
9
10
Anion
0
8
10
Anion
Mg
12
10
Cation
VALENCE ELECTRONS
An ion loses or gains electrons to form a stable octet.
Ions and noble gases can have the same amount of electrons and
same configuration!
Example: K+ 18 electrons
Cl- 18 electrons
[Ar] 18 electrons
CHARACTERISTICS/PROPERTIES
An ion has the same nucleus (number of protons and neutrons) as its
parent atom, but a different number of electrons.
Chemical properties of an atom depend on number and electron
configuration, so the ion has different chemical properties than its
parent atom.
Example: Sodium ions do not react violently in water, because they
have a stable noble gas configuration. Although stable, like the noble
gas, the ions have electrical charge- allowing them to conduct
electricity and form compounds.
IONIC BONDING/SALTS
Holt. Chapter 5, Section 2.
KEY TERMS
Salt – An ionic compound that forms when a metal atom combines with
a nonmetal.
Crystal Lattice – Regular pattern in which a crystal is arranged
Unit Cell – Smallest portion of a crystal lattice that shows the threedimensional pattern of the entire lattice.
IONIC BONDING –
Ionic bonds are formed by the difference in charges between to ions.
The positive ion is attracted to the negative ion.
IONIC COMPOUNDS
Ionic compounds, compounds formed by the bonding of positive cations
with negatively charge anions, are called salts.
Salts are electrically neutral compounds [NO CHARGE]
Electrostatic forces are so strong, that each cation attracts several
anions, pulling together into a tightly packed structure. Salts are made
of several cations and anions bonded together in specific ratios.
FORMATION OF IONIC COMPOUNDS
When the metal donates an electron, it forms a cation, and becomes
smaller.
When the nonmetal gains the electron, it forms an anion, and becomes
larger.
OPPOSITES ATTRACT.
Large anions surround themselves with smaller cations, and cations
attract anions forming a crystal lattice with repeating units.
Salts are made of unit cells (smallest repeating unit) that have an
organized, tightly packed structure.
The crystal lattice arrangement will depend on the ratio of cations to
anions, as well as, the relative sizes of cations to anions. Crystalline
structures are 3D.
PROPERTIES OF IONIC COMPOUNDS
- Ionic bonds usually form between atoms with large electronegativity differences.
- Ionic bonds are STRONG. There are large attractive forces between oppositely charged
atoms in a crystal.
- Ions are tightly packed due to large attractive forces.
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Solids at room temperature
High Melting Point
High Boiling Point
Hard and Brittle
Unable to conduct electricity in solid form due to limited movement
- Ionic compounds have a neutral (0) overall charge.
*Dissolved ionic compounds and melted salts are great conductors of electricity as their
charged particles can move freely.* Ionic compounds conduct electricity when dissolved in
water!!
IONIC FORMULA
WRITING/NAMING INTRO
Section 3.
IONIC BONDS
1.
Ionic compounds or salts are formed from the attractive forces
between ions.
2.
Ionic compounds have a OVERALL NEUTRAL CHARGE
3.
Ionic compounds are formed when atoms donate and accept
electrons. Electrons are taken, not shared!
4.
This means, the oxidation numbers of the cation and anion must
cancel out when they form a salt.
OXIDATION NUMBER
Charge when atom becomes ion
Examples:
 Oxygen (2 electrons gained)
2oxygen
 Calcium (2 electrons removed)
2+
Oxygen ion
WRITING COMPOUNDS
1. Use element symbols when writing compounds
 Sodium: Na; Calcium: Ca
2. Use subscripts to communicate how many of each atom you have.
Subscripts are numbers in the lower corner of the atomic symbol.
Example: Na2O
3. NO SUPERSCRIPTS (charges) in compounds. You do not need to
write charges.
4. Use parenthesis if more than one group of atoms.
IONIC COMPOUNDS
Examples:
Calcium and oxygen
 Ca2+ + O2 CaO
Sodium and Chlorine
 Na+ + Cl NaCl
Note: In both cases, the charges are
not shown when writing the formula
for the ionic compound!
In both examples, the cation and
anion have equal/opposite charges
which cancel out!
IONIC COMPOUNDS
Magnesium and Fluorine
 Mg2+ + F MgF2
Barium and Nitrogen
 Ba2+ + N3 Ba3N2
Note: In these examples, we must
balance the charges of the cation
and anion. They are opposite, but
not equal!
TRANSITION METALS (D-BLOCK)
Do not always have the same oxidation number.
Oxidation number (charge) is indicated by roman numerals in name.
Always cations, always positively charged.
Example:
Fe 2+ Fe 3+
Iron (II)
Iron (III)
EXAMPLES OF COMMON TRANSITION
METALS…
Name
Symbol & Charge
Iron (II) and Iron (III)
Fe2+ , Fe3+
Copper (I) and Copper (II)
Lead (II) and Lead(IV)
Gold (I) and Gold (III)
Mercury(I) and Mercury(II)
Cobalt (II) and Cobalt (III)
Tin (II) and Tin (IV)
Chromium (II) and Chromium (III)
NAMING IONIC COMPOUNDS
List the names of ions
CATION first, ANION last
NAMING IONIC COMPOUNDS
CATION:
 Use element name only!
 i.e. Calcium 2+ ion = “calcium”
 Transition metals have roman numerals as middle names to indicate
their charge  Iron (II), Fe2+
ANION:
 Change element ending to “ide”
 i.e. oxygen 2- ion = “oxide”
 i.e. Fluorine 1- ion = “fluoride”
NAMING IONIC COMPOUNDS We need to look at the overall
Name this:
 NaCl
 Sodium chloride
charge of the anion to make sure we
write in the correct cation charge!
Fe3N2
 Iron (II) nitride
Example: Nitride has a charge of -3.
There are 2 nitrides, so the overall charge of the anion is -6.
 Be3N2
The overall charge of the cation must be +6. Because there are 3
irons, the charge of each iron atom is +2.
 Beryllium nitride
CuO
 Copper (II) oxide
CoCl3
 Cobalt (III) chloride