Bonding and Naming in Chemistry: Types of Bonds, Valence Electrons, and Ionic vs. Covalent Compounds

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Bonding and Naming in Chemistry

Introduction to Types of Bonds

Chemical bonds are the forces that hold atoms together in compounds. These bonds can be formed between atoms of the same element (e.g., O2) or different elements (e.g., NaCl, CH4). The type of bond formed affects the chemical and physical properties of the resulting compound, including reactivity and stability.

Chemical bonds are created for elements to acquire a full valence electron octet (8 electrons in the outermost shell).
Ionic bonds occur when electrons are transferred from one atom to another, resulting in the formation of ions.
Covalent bonds occur when electrons are shared between atoms.
Noble gases (Group 8A/18) have a full octet and typically do not participate in bonding.

Vocabulary Review

Matter: Anything that occupies space and has mass.
Element: A pure substance consisting of one kind of atom.
Atom: The smallest part of an element that retains its properties.
Nucleus: The center of the atom containing protons and neutrons.
Proton: Subatomic particle with a positive charge.
Neutron: Subatomic particle with no charge.
Electron: Subatomic particle with a negative charge.
Ion: Charged particle (unequal number of protons and electrons).
Mixture: Combination of two or more elements or compounds physically mixed but not chemically combined.

Valence Electrons and the Periodic Table

Valence electrons are the electrons in the outermost shell of an atom and are crucial for chemical bonding. The number of valence electrons for each element can be determined from its group number in the Periodic Table.

Group Number	Valence Electrons
1A (1)	1
2A (2)	2
3A (13)	3
4A (14)	4
5A (15)	5
6A (16)	6
7A (17)	7
8A (18)	8

Atoms are electrically neutral when the number of electrons equals the number of protons.

Ionic Bonds

Ionic bonds form between metals and nonmetals when electrons are transferred from one atom to another, resulting in the formation of ions. The resulting positive and negative ions are attracted to each other due to opposite charges.

Cation: Positively charged ion (atom loses electrons).
Anion: Negatively charged ion (atom gains electrons).
Example: If a carbon atom (atomic number 6) loses 4 electrons, its charge becomes (cation). If an atom gains electrons, the charge becomes negative (anion).

Atoms with 4 or fewer valence electrons tend to lose electrons (form cations), while those with 4 or more tend to gain electrons (form anions). The goal is to achieve a full octet (8 valence electrons).

Monatomic Ions and Their Nearest Noble Gases	Charge
Na+ (Sodium)	+1
Mg2+ (Magnesium)	+2
Cl- (Chlorine)	-1
O2- (Oxygen)	-2
N3- (Nitrogen)	-3
Ne (Neon, noble gas)	0

Example: Formation of NaCl (Sodium Chloride)

Sodium (Na) has 1 valence electron and transfers it to chlorine (Cl), which has 7 valence electrons.
After transfer, both ions achieve a full octet: Na+ and Cl-.
The resulting ionic bond is due to the attraction between the oppositely charged ions.

Brain Check: Predicting Ion Charges

Potassium (K): Lose 1 electron (forms K+)
Xenon (Xe): None (already has 8 valence electrons)
Strontium (Sr): Lose 2 electrons (forms Sr2+)
Iodine (I): Gain 1 electron (forms I-)
Phosphorus (P): Gain 3 electrons (forms P3-)
Oxygen (O): Gain 2 electrons (forms O2-)

Covalent Bonds

Covalent bonds form when atoms share valence electrons to achieve a full octet. This type of bond typically occurs between nonmetal elements, especially those on the right side of the Periodic Table. Covalent bonds are not based on attraction of opposite charges, but on the sharing of electrons.

When two electrons are shared, it is a single bond.
When four electrons are shared, it is a double bond.
When six electrons are shared, it is a triple bond.

Bond Type	Number of Electrons Shared
Single	2
Double	4
Triple	6

Examples: O2 (oxygen gas) has a double bond; CH4 (methane) has single bonds between carbon and hydrogen.

Comparing Ionic and Covalent Bonds

Both types of bonds involve electrons and elements seeking to achieve a full octet.
Ionic bonds: Electrons are transferred; typically form between metals and nonmetals.
Covalent bonds: Electrons are shared; typically form between nonmetals.
Exception: Hydrogen and helium only need 2 valence electrons to be stable.

Summary Table:

Bond Type	Formation	Elements Involved
Ionic	Transfer of electrons	Metal + Nonmetal
Covalent	Sharing of electrons	Nonmetal + Nonmetal

Additional info: Lewis Dot Structures are used to represent covalent bonds and will be covered in more detail later in the course.