Ionic and Covalent Bonding
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Describe the formation of cations.
when an atom loses electron(s)
Are metals always cations or anions?
cations
What is a cation?
positively charged ions
What is an anion?
negatively charged ions
Describe the formation of anions.
when an atom gains electron(s)
What is the relationship between group number and the charge of ions formed from that group?
usually, elements form cations which charge = group number usually, elements form anions which charge = 8 - group number (transition metals have variable oxidation numbers)
What are the oxidation numbers of transition metals?
variable oxidation numbers
What type of elements have variable oxidation numbers?
transition elements
What is an ionic bond?
a strong electrostatic attraction between oppositely charged ions
Describe the properties of ionic compounds.
• high melting points and boiling points • good electrical conductivity when aqueous or molten and poor when solid
Describe the giant lattice structure of ionic compounds.
a regular arrangement of alternating positive and negative i ons
Ionic compounds are arranged in…
giant lattice structures
Ionic bonds are formed between _____.
metals and non-metals
Metals and non-metals form…
ionic bonds
Why do ionic substances have high melting/boiling points?
electrostatic forces holding ions together are very strong, a lot of energy needed to separate the ions
Why do ionic substances only conduct when molten or aqueous, not solid?
• ions in solid unable to move freely (conduction of electricity occurs when ions can move freely, carrying charge) • in molten/aqueous solution, ions are free to move and carry charge
When is a covalent bond formed?
when a pair of electrons is shared between atoms leading to noble gas electronic configurations
What is a covalent bond?
a shared pair of electrons
A covalent bond forms between ______.
two non-metals
Two non-metals bond ______.
covalently
What are properties of simple molecular compounds (covalent)?
• low melting/boiling points • poor electrical conductivity
Why do simple covalent compounds have low melting/boiling points?
weak intermolecular forces between molecules
Why do simple covalent compounds not conduct electricity?
no overall charged particles in molecules which can move freely through the structure
In covalent molecules, how does size affect melting/boiling points?
the larger the molecule, the higher the melting/boiling point: greater number of weak intermolecular forces between molecules, which need more energy to overcome