Question

Describe the formation of ionic and covalent compounds.

Identify a compound as ionic or covalent.

Using charge balance, write the correct formula for an ionic compound (including those with polyatomic ions).

Write the correct molecular and empirical formula for molecular compounds.

Given the formula of a covalent or ionic compound (including polyatomic ions), write the correct name.

Apply the basic rules guiding Lewis dot structures to draw the configuration for individual atoms, ionic compounds (including those with polyatomic ions), and covalent compounds (including those with double and triple bonds).

Apply the VSEPR theory to model the shape of a molecule.

Given an atom's electronegativity, proceed from predicting the bond type and bond polarity to predicting molecule polarity (based on molecular shape).

Answer 1

Describe the formation of ionic and covalent compounds.

An ionic compound is formed by the union of a metal element (generally of group I and II of the periodic table) and another non-metal element, whose electronegativity is greater. They are bonds that originate from the exchange of electrons; more electronegative element captures the valence electrons of the less electronegative element, generating between them both an energetic stability due to this exchange.

For example:
Mg⁺² + Cl^-1 MgCl₂. In this example the magnesium gives two electrons to the chlorine, leaving both with their respective charges and a strong attraction is generated between them, completing the stable bond.

A covalent compound is one that is formed by the union of non-metallic elements. It is a bond that occurs due to the sharing of electrons between the elements that make up the compound; that is, when two or more elements are covalently linked, their stability is achieved thanks to the fact that they share the electrons that each one needs to reach its minimum energy state.

For example:
H + O H₂O / H-O-H. In this example it is observed how oxygen shares two pairs of electrons with two hydrogens, each one completing its level of stability. Each "-" represents an electronic pair or a covalent bond.

Identify a compound as ionic or covalent.

Ionic Compound:
Metal (usually group I and II) + Non-metal (very electronegative) (e.g. NaCl)

Covalent Compound:
Inorganic: Non-metal + Non-metal (e.g. H₂S)
Organics: All (e.g. CH₄)

Using charge balance, write the correct formula for an ionic compound (including those with polyatomic ions).

Na⁺¹ + Cl^-1 NaCl
Mg⁺² + 2Cl^-1 MgCl₂
2Na⁺¹ + (SO4)^-2 Na₂SO₄

In the previous examples, the charge balance of each ionic compound is highlighted, that is, the number of cations and anions must be the same in order to obtain the stable compound.

Write the correct molecular and empirical formula for molecular compounds.

The empirical formula indicates only the proportion of atoms in a compound and the molecular formula tells the number of atoms in a molecule.

For example: the general molecular formula of the alkanes is C_nH_2n+2, where "n" is the number of carbon atoms that the compound has.
Hexane: C₆H₁₄ means there are 6 carbon atoms and 14 hydrogen atoms. On the contrary, its empirical formula is C₃H₇, which means that there are 7 hydrogen atoms for every 3 carbon atoms or vice versa.

Given the formula of a covalent or ionic compound (including polyatomic ions), write the correct name.

C₄H₁₀ = Butane
CaCl₂ = Calcium Chloride
KMnO₄ = Potassium Permanganate