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 more reactive than carbon who needs 4.

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 three-dimensional 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. 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

INTROSection 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)

2-

Calcium (2 electrons removed)

2+

oxygen 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

Name this:NaCl

Sodium chloride

Be3N2 Beryllium nitride

Fe3N2 Iron (II) nitride

Example: Nitride has a charge of -3.

There are 2 nitrides, so the overall charge of the anion is -6.

The overall charge of the cation must be +6. Because there are 3 irons, the charge of each iron atom is +2.

CuO Copper (II) oxide

CoCl3 Cobalt (III) chloride

We need to look at the overall charge of the anion to make sure we write in the correct cation charge!