Chem Chapter 5

Ionic Compounds

Formed between a metal + nonmetal through the transfer of electrons (forming positive cations and negative anions). Held together by strong ionic bonds/electrostatic attraction; typically have high melting points and conduct electricity in water.

Covalent Compounds

Formed between two nonmetals through the sharing of electrons (forming neutral molecules).

Cations

positively charged ions formed by losing electrons,

Anion

negatively charged ions formed by gaining electrons

Octet Rule

Atoms gain or lose valence electrons to reach a full outer shell (usually 8 valence electrons, or 2 for Helium)

Metal Strategy

Lose electrons to form positive ions (cations).

Nonmetal Strategy

Gain electrons to form negative ions (anions).

Metal strategy example

($\text{Na}$): $1s^2 2s^2 2p^6 3s^1 \rightarrow$ Loses $1\text{ e}^-$ to become $\text{Na}^+$ ($1s^2 2s^2 2p^6$).

Nonmetal strategy example

O $1s^2 2s^2 2p^4 \rightarrow$ Gains $2\text{ e}^-$ to become $\text{O}^{2-}$ (1s^2 2s^2 2p^6

ion

an electrically charged particle formed

when electrons are gained or lost by an atom.

polyatomic ion

a charged group of multiple atoms joined together by covalent bonds that acts as a single unit

Common polyatomic ions

• Nitrate: $\text{NO}_3^-$

• Hydroxide: $\text{OH}^-$

• Sulfate: $\text{SO}_4^{2-}$

• Carbonate: $\text{CO}_3^{2-}$

• Phosphate: $\text{PO}_4^{3-}$

How to spot polyatomic ions

3 capital letters in formula, ends in ate or ite, exeptions Hydroxide & Cyanide! (ide usualy mean monoatmic)

Simple bianary

2 elements only (ends in -ide)

Needs a Roman numeral when being written into forumla

Transition Metal (like $\text{Fe}, \text{Cu}, \text{Ni}$)

Writing Chemical formula

• Swap charges to become subscripts.

• If a polyatomic ion needs a subscript of 2 or more, wrap it in parentheses: $\text{(NO}_3)_3$.

• If it only needs a 1, no parentheses needed:

Writing Chemical formula example

Calcium sulfate

Calcium is $\text{Ca}^{2+}$, Sulfate is $\text{SO}_4^{2-}$.

Because both subscripts are $2$, they reduce $2:2 \rightarrow 1:1$.

$\text{CaSO}_4$.

Writing transition metal formula

• Find the total negative charge: Multiply the charge of the negative ion by its subscript.

• Find the metal's charge: Divide that total positive charge by the metal's subscript to balance it.

• Write the Roman numeral: Put that metal's charge as a Roman numeral in parentheses right after the metal's name (O charge is -2) (e.g., $\text{PbO}_2 \rightarrow \text{Lead(IV) oxide}$).

To find charge of ion

• Start with the nonmetal (the known charge): Look up its fixed charge on the Periodic Table and multiply it by its subscript to get the total negative charge.

• Flip it to positive: The total positive charge must equal the exact same number to balance out to $0$.

• Divide by the metal: Divide that positive total by the metal's subscript to find the charge of a single metal ion.

Finding charge of ion example

SnO2; Oxegen charge(known) -2, Two oxegens so charge is -4, Flip it for Sn(Must be balanced) answer Sn charge = +4