Bonding/Nomenclature

What is the octet rule?

Atoms bond to achieve 8 valence electrons for stability.

Which elements are exceptions to the octet rule?

The first 5 elements ($ext{H}$, $ext{He}$, $ext{Li}$, $ext{Be}$, $ext{B}$) can’t reach 8 electrons.

Why do noble gases rarely bond?

They already have full valence shells (8 $e^{-}$, 2 for $ext{He}$).

What elements form ionic bonds?

Metal + nonmetal (or polyatomic ion).

What happens to electrons in ionic bonding?

Electrons are transferred from metal to nonmetal.

What elements form covalent bonds?

Nonmetal + nonmetal.

What happens to electrons in covalent bonding?

Electrons are shared between atoms.

What elements form metallic bonds?

Metal + metal.

What happens to electrons in metallic bonding?

Electrons move freely in a “sea of electrons.”

What is an ionic bond?

Electrostatic attraction between cations (+) and anions (–).

How does a metal become a cation?

By losing electrons.

How does a nonmetal become an anion?

By gaining electrons.

What do dots in Lewis diagrams represent?

Valence electrons.

How do you draw metal ions in Lewis diagrams?

Remove dots, use brackets with charge.

How do you draw nonmetal ions in Lewis diagrams?

Add dots to reach 8, use brackets with charge.

How do you combine ions in a diagram?

Place ions so total charge = $0$.

What is the first step in the X-cross method?

Write symbols with ion charges above them.

What is the second step?

Cross charges down to become subscripts.

What is the final step?

Simplify subscripts to lowest ratio.

Example of X-cross: $ext{Al}^{3+}$ & $ext{O}^{2-}$ → ?

$ext{Al}<em>2 ext{O}</em>3$.

Which has the largest atomic radius: $ext{Ca}$, $ext{As}$, or $ext{P}$?

ext{Ca} > ext{As} > ext{P}.

Which has the highest ionization energy: $ext{P}$, $ext{As}$, or $ext{Ca}$?

ext{P} > ext{As} > ext{Ca}.

Which has the highest electronegativity: $ext{P}$, $ext{As}$, or $ext{Ca}$?

ext{P} > ext{As} > ext{Ca}.

What is electronegativity of noble gases?

$0$; they don’t attract electrons.

What is a metallic bond?

Attraction between metal cations and delocalized electrons.

Why are metals conductive and malleable?

Free-moving electrons allow charge and flexibility.

How many electrons does $ext{Al}$ lose when bonding?

$3$, forming $ext{Al}^{3+}$.

How are valence electrons represented in Lewis diagrams?

Dots around an element symbol.

What’s the rule for dot placement?

Spread dots singly before pairing.

What does each dot represent?

One valence electron.

How many valence electrons does Group 1 have?

$1$.

How many does Group 18 have?

$8$ (except $ext{He}$ with $2$).

How do metals form cations?

Lose electrons → positive charge.

Example of metal ion formation?

$ext{Na}$ → $ext{Na}^{+}$ + $e^{-}$.}

How do nonmetals form anions?

Gain electrons → negative charge.

Example of nonmetal ion formation?

$ext{F}$ + $e^{-}$ → $ext{F}^{-}$.}

What charge does sodium form?

$+1$ ($ext{Na}^{+}$).

What charge does oxygen form?

$-2$ ($ext{O}^{2-}$).

What compound forms from $ext{Na}$ and $ext{O}$?

$ext{Na}_2 ext{O}$ (sodium oxide).

What’s the rule for ionic compound neutrality?

Total + = total – charge.

Why do transition metals have variable charges?

s and d orbitals overlap in energy.

What charge can iron form?

$ext{Fe}^{2+}$ or $ext{Fe}^{3+}$.

What is a polyatomic ion?

A covalently bonded group with an overall charge.

Can polyatomic ions be altered?

No, they must remain intact.

What endings do most polyatomic ions have?

“-ate” or “-ite.”

Example of a polyatomic ion?

$ext{ClO}^{-}$ (hypochlorite).

When are parentheses used in formulas?

When multiple identical ions are needed.

Example with parentheses?

$ext{Ca}<em>3( ext{PO}</em>4)_2$ (calcium phosphate).

What’s the purpose of crossing charges?

To balance positive and negative ions.

Example: $ext{Mn}^{4+}$ + $ext{OH}^{-}$ → ?

$ext{Mn}( ext{OH})_4$.

Example: $ext{K}^{+}$ + $ext{SO}_4^{2-}$ → ?

$ext{K}<em>2 ext{SO}</em>4$.

What elements form covalent bonds?

Nonmetals only.

How do electrons behave in covalent bonds?

Shared between atoms.

Example of a covalent compound?

$ext{H}_2 ext{O}$ (water).

Example of an ionic compound?

$ext{Na}_2 ext{O}$ (sodium oxide).

What does VSEPR stand for?

Valence Shell Electron Pair Repulsion.

What’s the first step in drawing Lewis structures?

Count total valence electrons.

Which atom is usually central?

Least electronegative (never $ext{H}$).

What’s the purpose of formal charge?

To find the most stable structure.

Linear geometry: domains and angle?

$2$ domains, $180^{\circ}$.

Trigonal planar geometry: angle?

$120^{\circ}$.

Tetrahedral geometry: angle?

$109.5^{\circ}$.

Bent molecule: bonding + lone pairs?

$2$ bonds, $1$ lone pair.

Trigonal pyramidal: bonding + lone pairs?

$3$ bonds, $1$ lone pair.

How are binary covalent compounds named?

First element normal; second with “-ide.”

When is “mono-” used?

Only on the second element.

Prefix for $2$ atoms?

di-

Prefix for $3$ atoms?

tri-

Prefix for $4$ atoms?

tetra-

Prefix for $5$ atoms?

penta-

Prefix for $6$ atoms?

hexa-

Example: $ext{CF}_4$ name?

Carbon tetrafluoride.

Example: $ext{N}<em>2 ext{O}</em>4$ name?

Dinitrogen tetroxide.

What is a covalent bond?

Sharing of valence electron pairs between nonmetals.

How many pairs are shared in single, double, and triple bonds?

$1$, $2$, and $3$ respectively.

Which bond type is strongest?

Triple bond.

Which has a $109.5^{\circ}$ bond angle?

Tetrahedral molecules.

What happens when a bond forms?

Energy is released.

Why are triple bonds hard to break?

They have high bond energy.

Can $ext{H}$ be central in Lewis structures?

No, it’s always terminal.

What do you do if the central atom lacks an octet?

Convert lone pairs to multiple bonds.

Formula for formal charge?

Valence – (lone + $\frac{1}{2}$ bonding).