How do I decide whether a bond is ionic, covalent or metallic?

Look at the elements and their electronegativity difference. A metal with a nonmetal usually gives an ionic bond (electrons transferred, difference roughly above 1.7). Two nonmetals share electrons in a covalent bond: nonpolar if the difference is about 0 to 0.4 and polar if about 0.4 to 1.7. Two metals give a metallic bond, with cations in a sea of delocalized electrons. The boundaries are guidelines, so use the metal-versus-nonmetal check alongside them.

How do I draw a Lewis structure and predict the shape?

Total the valence electrons, place the least electronegative atom (never hydrogen) in the center, bond the outer atoms with single bonds, distribute the rest as lone pairs, and form double or triple bonds if the center lacks an octet. Then apply VSEPR: count the electron pairs on the central atom. Two pairs give linear, three trigonal planar, four tetrahedral; lone pairs bend the shape, so a central atom with two bonds and two lone pairs is bent like water.

When is a molecule polar?

A molecule is polar only if it has polar bonds and an asymmetrical shape, so the bond dipoles do not cancel. Symmetrical molecules such as linear carbon dioxide or tetrahedral methane have polar bonds but cancel them out, so they are nonpolar overall. Bent water and pyramidal ammonia are asymmetrical, so their dipoles add up and the molecules are polar.

What are the intermolecular forces and how do they affect properties?

From weakest to strongest: London dispersion forces (in all molecules, stronger in larger ones), dipole-dipole forces (between polar molecules), and hydrogen bonding (a strong dipole force when hydrogen is bonded to nitrogen, oxygen or fluorine). Stronger forces mean higher boiling and melting points and lower volatility. Solubility follows like dissolves like: polar dissolves polar, nonpolar dissolves nonpolar.

How do I name compounds and write formulas?

For ionic compounds, balance the cation and anion charges into the smallest whole-number subscripts (crossover), with parentheses around a polyatomic ion used more than once, and a roman numeral giving a transition metal's charge. For binary molecular compounds (two nonmetals), use Greek prefixes and end the second element in -ide. For acids, a binary acid is hydro...ic acid, and an oxyacid comes from its polyatomic ion (sulfate gives sulfuric acid).

VirginiaChemistry

Virginia SOL Chemistry chemical bonding and nomenclature: a complete skills guide to bond types, Lewis structures, polarity, intermolecular forces and naming compounds

A deep-dive Virginia SOL Chemistry guide to chemical bonding and nomenclature (CH.3): ionic, covalent and metallic bonds, drawing Lewis structures and predicting shapes with VSEPR, molecular polarity and the intermolecular forces, and naming and writing formulas for ionic, molecular and acid compounds, with the periodic table and SOL exam technique.

Generated by Claude Opus 4.816 min readCH.3Updated 2026-06-13

Reviewed by: AI editorial process; not yet individually human-reviewed

Jump to a section

Why bonding and naming come together
Bond types
Lewis structures and shape
Polarity and intermolecular forces
Nomenclature
Check your knowledge

Why bonding and naming come together

Bonding (why and how atoms join) and nomenclature (the names and formulas of the compounds they form) are two halves of standard CH.3 and of the second SOL reporting category. Bond type sets a substance's properties, shape sets its polarity, and a correct formula is the gateway to every later calculation. This guide ties together the matching dot-point pages, each with its own practice: types of chemical bonds, Lewis structures and molecular geometry, polarity and intermolecular forces, and naming compounds and writing formulas.

Bond types

Atoms bond to reach a stable octet. Ionic bonds transfer electrons from a metal to a nonmetal, forming a lattice of attracting ions (high melting point, conducts when molten or dissolved). Covalent bonds share electrons between nonmetals, nonpolar when shared equally and polar when shared unequally. Metallic bonds hold metal cations in a sea of delocalized electrons (conducts, malleable). The electronegativity difference predicts the type: large gives ionic, moderate gives polar covalent, near zero gives nonpolar covalent.

Lewis structures and shape

Build a Lewis structure by totaling valence electrons, centering the least electronegative atom, bonding with single bonds, then adding lone pairs and forming multiple bonds to complete octets. VSEPR then predicts shape from the electron pairs on the central atom:

Electron pairs	Lone pairs	Shape	Example
2	0	linear	$\text{CO}_2$
3	0	trigonal planar	$\text{BF}_3$
4	0	tetrahedral	$\text{CH}_4$
4	1	trigonal pyramidal	$\text{NH}_3$
4	2	bent	$\text{H}_2\text{O}$

Polarity and intermolecular forces

A molecule is polar only if it has polar bonds and an asymmetrical shape, so symmetry cancels dipoles (linear $\text{CO}_2$ is nonpolar; bent $\text{H}_2\text{O}$ is polar). The intermolecular forces rank from weakest to strongest as dispersion, dipole-dipole, then hydrogen bonding (H bonded to N, O or F). Stronger forces raise boiling and melting points; solubility follows "like dissolves like".

Nomenclature

A correct formula is neutral. For ionic compounds, cross over the charges to the smallest whole-number subscripts, use parentheses for a repeated polyatomic ion, and read a roman numeral as the metal's charge. For binary molecular compounds, use prefixes (di-, tri-, tetra-) and an -ide ending. For acids, binary acids are hydro...ic, and oxyacids come from their polyatomic ions.

A combined bonding and naming problem

For magnesium chloride: (a) state the bond type, (b) write the formula, and (c) state whether it conducts electricity as a solid.

step 1 Bond type

Magnesium is a metal and chlorine is a nonmetal with a large electronegativity difference, so the bond is ionic.

step 2 Formula

Magnesium is $\text{Mg}^{2+}$ and chloride is $\text{Cl}^-$ ; crossing the charges gives one magnesium to two chloride: $\text{MgCl}_2$ .

step 3 Conductivity as a solid

As a solid the ions are locked in the lattice and cannot move, so $\text{MgCl}_2$ does not conduct; it conducts only when molten or dissolved.

step 4 Check

The name uses no prefix because it is ionic, and the formula is neutral ( $1 \times 2+ = 2 \times 1-$ ), so the answer is consistent.

Atoms bond to reach a stable octet: ionic bonds transfer electrons (metal plus nonmetal, conduct only when molten or dissolved), covalent bonds share electrons between nonmetals (polar or nonpolar by electronegativity difference), and metallic bonds hold cations in a sea of electrons. Draw Lewis structures by totaling valence electrons and completing octets, then use VSEPR (two pairs linear, three trigonal planar, four tetrahedral, lone pairs bend the shape). A molecule is polar only with polar bonds and an asymmetrical shape. Intermolecular forces rank dispersion, dipole-dipole, hydrogen bonding, and stronger forces raise boiling points. Name ionic compounds by balancing charges (parentheses for repeated polyatomic ions, roman numerals for transition metals), molecular compounds with prefixes, and acids as hydro...ic or from their oxyanions.

Check your knowledge

Attempt these under timed conditions, then check the solutions.

Classify the bond in potassium fluoride and explain your reasoning. (2 marks)
Draw the Lewis structure of water and state its molecular shape. (2 marks)
Explain why carbon dioxide is nonpolar despite having polar bonds. (2 marks)
Identify the strongest intermolecular force in ammonia, $\text{NH}_3$ . (1 mark)
Write the formula for aluminum oxide. (1 mark)
Name the compound $\text{P}_2\text{O}_5$ . (1 mark)

Sources & how we know this

2018 Science Standards of Learning - Chemistry — Virginia Department of Education (2018)
Chemistry Curriculum Framework — Virginia Department of Education (2018)