Ionic and Covalent Compounds Notes

Elements and Compounds

Elements

Elements are matter made of only one type of atom.
Example: Helium gas in a balloon is made only of helium atoms.
Example: Oxygen gas (O2) is made only of oxygen atoms bonded together.
All elements are listed in the periodic table.

Compounds

Compounds are matter made of two or more different types of atoms.
Atoms are held together by chemical bonds.
Example: Water (H2O) is made of hydrogen and oxygen atoms.
Example: Caffeine is a compound made of carbon, nitrogen, hydrogen, and oxygen atoms.
Chemical bonds hold atoms together in a compound.

Types of Chemical Bonds

Ionic Bonds: Valence electrons are transferred.
Covalent Bonds: Valence electrons are shared.

Types of Compounds

Ionic Compounds: Held together by ionic bonds.
Covalent Compounds: Held together by covalent bonds.
There are many more compounds than elements.

Why Compounds Form

Atoms combine to form compounds to achieve stability.
Compounds have lower potential energy than separate atoms.
Systems tend towards stability by losing energy.
Atoms with partially filled valence shells attain filled status when forming compounds.
Atoms achieve a noble gas configuration when they form compounds.

Ionic Compounds

Also known as salts.
Composed of oppositely charged ions.
Example: Sodium chloride (NaCl) is made of sodium positive and Cl negative.
Ions are species with a charge (positive or negative).

Monoatomic Ions

Ions made up of one atom.
Example: Sodium positive, Cl negative.
Opposite charges attract each other, forming an ionic bond.
Ionic bond is a force of attraction between positive and negative charges.
Monoatomic ions are formed when a metal loses an electron, and a nonmetal gains it.
Example: Sodium (Na) has 11 protons and 11 electrons, making it neutral.
If sodium loses an electron, it becomes a sodium cation (Na+) with 11 protons and 10 electrons, resulting in an overall +1 charge.
Loss of electron results in positive charge (cation).
Fluorine (F) has nine protons and nine electrons, making it neutral.
If fluorine gains an electron, it becomes a fluoride anion (F-) with nine protons and 10 electrons, resulting in an overall -1 charge.
Gain of electron results in negative charge (anion).
Cation: Positive charge.
Anion: Negative charge.

Formation of Ionic Compounds

Neutral metal atoms lose electrons to form positive cations.
Neutral nonmetal atoms gain electrons to form negative anions.
Example: Sodium atom (11 protons, 11 electrons) loses an electron to become a sodium cation (Na+).
Chlorine atom (17 protons, 17 electrons) gains an electron to become a chloride anion (Cl-).
Opposite charges attract each other, forming an ionic bond.
Multiple atoms form a crystalline structure, such as a sodium chloride crystal.
The ratio of positive to negative charges is always the same (e.g., 1:1 in NaCl).
The formula represents the ratio of ions, not the total number in the crystal.
The net charge in the crystal is zero.

Properties of Ionic Compounds

Different from the elements they are formed from.
Example: Sodium is a reactive, flammable metal, and chlorine is a toxic gas. When combined, they form harmless sodium chloride (table salt).
Ionic compounds are held together by strong attraction of opposite charges.
When a cation and anion have same charges, the ratio will be one:one.
If charges are not the same magnitude, more ions are needed to neutralize the charges (e.g., Na2S).
Subscripts represent how many ions of each element are present in ionic compound.

Electrolytes

Ions that conduct electricity when dissolved in water.
Important in human body for transmitting signals from brain to muscles and organs.
Examples: Sodium, potassium, calcium, chloride.
Sodium and potassium regulate blood pressure.
Calcium is important for bone health.

Determining Cation Charge Using Periodic Table

The periodic table can be used to determine the charge and magnitude of cations formed from main group elements (groups with letter A).
Group 1A, 2A, and 3A elements lose all valence electrons when forming cations.
Elements in group 1A have one valence electron, group 2A have two, and group 3A have three.
Cation charge is the same as the group number.
Example: Sodium (group 1A) loses one electron to form Na+.
Example: Calcium (group 2A) loses two electrons to form Ca2+.
When elements lose valence electrons, their electron arrangement becomes similar to the nearest noble gas, making them stable.
Exceptions: Beryllium and boron do not easily lose electrons.

Energy Levels and Stability

Electrons at lower energy levels are more stable.
Each energy level has a maximum occupancy $2n^2$ , where $n$ is the energy level number.
Example: Neon has 10 protons and 10 electrons, with two electrons in the first level and eight in the second level. Both levels are full, making it stable.
Sodium has 11 protons and 11 electrons, with two electrons in the first level, eight in the second level, and one in the third level. The third level is not full, making it unstable.
When sodium loses the electron in the third level, it becomes Na+ with the same electron configuration as neon, making it stable.
Magnesium has 12 electrons. When it loses two electrons, it becomes $Mg^{2+}$ and becomes stable

Variable Charges

Group 4A and transition metals do not lose all their valence electrons and can lose variable numbers of electrons in becoming cations.
Iron can lose two electrons (Fe2+) or three electrons (Fe3+).
Roman numerals are used to specify the charge (e.g., iron(II) or iron(III)).
Exceptions: Silver is always one positive ( $Ag^+$ ), and zinc is always two positive ( $Zn^{2+}$ ).

Heavy Metals and Toxicity

Lead (Pb) and mercury (Hg) are heavy metals that form different ions.
Lead II ( $Pb^{2+}$ ) and mercury I ( $Hg^+$ ) are poisonous and harmful to developing brains.
Lead-based paint and leaded fuel have been banned due to toxicity.

Nonmetals and Anion Formation

Nonmetals gain electrons to achieve a noble gas configuration, becoming negatively charged anions.
Fluorine needs to gain one electron to have eight valence electrons. Fluorine becomes fluoride once it gains an electron.
The charge of an anion from a nonmetal is equal to group number minus eight.

Naming Anions

Change the name and add "-ide" at the end.
Chlorine (Cl) becomes chloride.
Fluorine becomes fluoride.
Oxygen becomes oxide.
Sulfur becomes sulfide.
Phosphorus becomes phosphide.
Nitrogen becomes nitride.

Practice Problems

Cesium (Cs) transfers electron to bromine (Br).
Cesium is in group 1A (one valence electron, +1 charge).
Bromine is in group 7A (needs one electron, -1 charge).
$Cs + Br \rightarrow Cs^+ + Br^-$

Ions: Protons and Electrons Example

In an atom, number of protons = number of electrons and number of protons = atomic number
Iodide ion (I-): Iodine has 53 protons
Phosphide ion ( $P^{-3}$ ): Phosphorus has 15 protons
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Writing Formula Units for Ionic Compounds

An ionic compound is represented by a formula unit specifying cations and anions.
The atomic symbol for cation is always written first, followed by the symbol for the anion.
Charges are excluded when writing the formula
Subscripts indicate the lowest whole number ratio of cation to anion. Examples: NaCl, MgO.
The sum of charges on cations and anions must be equal to zero.

Writing Formulas with Unknown Charges

Find the symbol for calcium (Ca) and the symbol for oxygen (O).
Find the charges on ions. Calcium is in group 2A (+2 charge), and oxygen is in group 6A (-2 charge).
Determine the number of ions needed on each side. 1 Ca and 1 O is needed so $\rightarrow CaO$
One to One ratio of ionic compounds: K9 to A9 ratio is one is to one meaning calcium oxide one calcium cancels out oxide

Calcium and Oxygen Ratio

If we write the ionic compound formula between sodium and oxygen, it will be different
Symbol: Sodium is Na and oxygen is O
Charge: the sodium charge is +1 oxygen charge is -2 so: $Na_2O$
Magnesium and Nitrogen Ratio: Magnesium is Mg +2 and nitrogen is N -3 which leads to : $Mg3N2$

Nomenclature

Writing names of chemical compounds is known as nomenclature
Naming ionic compounds is simple
Rules: Write the name of the cation/metal, then write the name of the anion/nonmetal.
We do not use information about the subscript in the name
Example: magnesium nitride (Mg3, $N2$ ), calcium bromide ((Ca $Br2$ )

To name the metals when they vary charges using Roman numerals specify the charge of the metal:

Examples include iron(II) chloride and iron(III) chloride

Common Examples of ionic compounds in foods

Calmatine lotion contains zinc oxide.
Sunscreen creams contain zinc oxide because zinc oxide blocks the sun's Rays
Toothpaste is an example that uses sodium fluoride which is effective at strengthening the teeth

Practice: Writing the name when the formulas are known

Sodium sulfide the metal is sodium and the nonmetal is sulfur. The final correct answer is is two part two sodium's to one sulfur
Magnesium Nitride. 3 magnesiums and two nitrogens cancel each other out with charge leading 10 $Mg3N2$

Writing names with when the formulas

Sodium oxygen. When oxygen takes form of an ION it takes the name oxide leading to Sodium oxide with formula: $Na_2O$
The name of calcium is Magnesium Iodine. The correct formula magnesium iodide is written as ( $MgI_2$ )
Potassium has a value of+1 and chlorine forms chloride (-1). Together they formula Potassium cholride or KCl
Zinc has a value of +2 and an oxygen is -2 so they form Zinc Oxide (ZnO)

Polyatomic Ions

Poly means many, Polyatomic means that there are many atoms in the ion
There is an unequal number of product protons and electrons with in a polyatomic ion that creates a net charge
Each polyatomic has a name, unique formulas, and a memorized charge that it takes
Very well known example is sulfate
Table 3.3 are common polyatomic ions includes sulfate which has the formula of $SO4$ , to negative, nitrate is given by $NO3^-$ , ammonium = $NH_4^+$
Derive from molecules not atoms
Composed of at least one covalent bond
Unequal number of product proteins and electrons lead to overall charge
Unique name for all

Writing Formulas of Ionic Compounds with Polyatomic Ions

Use the same procedure for polyatomic except you must use parenthesis:
Example- Magnesium with chloride forms Magnesium $Cl_2$ without using the parenthesis!

If you want to write out for magnesium hydroxide
It will be Mg (OH)2 so that you know the entire unit is repetitive twist

Naming for these is more simple. You use the form: name of metal plus the name of polyatomic I am such.

Sodium. $CO_3$ (carbonate) = sodium carbonate
Need to find out what the charge is

Polyatomic in Nature and Consume Goods

Bleach, tooth paste, mouth wash, sodium nitrate
Hypochloriated is active in gradients found in Bleach, which kills bacteria
Sodium nitrate/ nitrite are usually preservatives found in meats with a formula of NaNo3 (nitrite NaNo2)
Our natural tooth animal contains the polyatomic hydroxyl appetite as well as phosphate, hydrogen and phosphate is good to help keep the teeth enamel strengthened