topic 3 - bonding Flashcards
Explain the formation of ions in ionic compounds from their atoms, in groups 1, 2, 6 and 7
Groups 1+2: lose electrons to form cations
Groups 6+7: gain electrons to form anions
When are the endings -ide and -ate used?
-ide: an anion that contains oxygen and at least one other element
-ate: an anion that contains only one element
How do you find the formula of an ionic compound by balancing charges?
The charges of ions need to be balanced.
To make a neutral compound one cation needs to combine with an anion - this pairing ensures the compound has an overall neutral charge
Explain the structure of an ionic compound
- Lattice structure formed by strong attractions between oppositely charged ions
- Due to the powerful electrostatic forces between the ions, the compound has a HMP/HBP
How is a covalent bond formed?
When a pair of electrons is shared between two atoms. This helps them reach a stable state and achieve a strong bond
What is the result of covalent bonding?
Molecules are formed, where atoms share electrons to form stable units
Recall the typical size (order of magnitude) of atoms and small molecules
Atom: typically about 0.1 to 0.5 nanometres
Small molecules: range from about 0.1 to a few nanometers in size
What do dot and cross diagrams represent?
the outer shell electrons of each atom using dots for one element and crosses for another element.
Hydrogen (H2) - Dot and cross
- Sharing single electron
- single covalent bond
- diagram displays 2 hydrogen atoms sharing a pair of electrons
Hydrochloric acid (HCl) - Dot and cross
- H + Cl share an electron to form a single covalent bond
- hydrogen has 1 electron and chlorine has 7, indicating their sharing to complete their outer shells
Water (H2O) - dot and cross
- O2 shares 2 electrons with 2 hydrogen atoms to form 2 covalent bond
- diagram shows O2 sharing 2 pairs of electrons, 1 pair with each hydrogen atom.
Methane (CH4) - dot and cross
- Carbon (C) forms 4 covalent bonds, each has 1 H atom by sharing its 4 outer electrons
- diagram shows C sharing 1 electron with each of the 4 H atoms.
Oxygen (O2) - dot and cross diagrams
- 2 O2 atoms share 2 pairs of electrons, forming a double covalent bond between them
- diagram displays both oxygen atoms sharing two pairs of electrons.
Carbon Dioxide (CO2) - dot and cross
- 1 C atom shares 2 pairs of electrons with 2 O atoms, forming 2 double covalent bonds
- diagram shows C sharing 2 pairs of electrons with each O atom.
Why can elements and compounds be classified as ionic?
Result from electron transfer between atoms, forming charged ions that attract each other.
Why can elements and compounds be classified as simple molecular (covalent)?
Atoms share electrons, forming weakly bonded molecules with lower melting points and no conductivity.
Why can elements and compounds be classified as giant covalent?
Feature strong covalent bonds in extensive networks, resulting in high melting points. Some, like graphite, can conduct electricity.
Why can elements and compounds be classified as metallic?
Comprised of metal atoms sharing a “sea” of electrons, leading to good conductivity and other typical metallic properties.
Explain how the structure and bonding of substances results in different physical properties
Why do ionic compounds have high melting/boiling points?
Due to strong electrostatic forces of attraction between oppositely charged ions, within the lattice structure. A lot of energy is needed to break this attraction.
Why do ionic compounds conduct electricity?
When molten and dissolved the ions become free to move and carry the electric charge. (Not in solids as the ions are fixed)
Properties of typical covalent, simple molecular substances:
- LMP/LBP
- Don’t conduct electricity
- Some are soluble in water, some aren’t
Why do typical covalent, simple molecular compounds have low melting/ boiling points?
Mostly gases or liquids at room temp, as the molecules get smaller, less energy is needed to break the weaker forces between them
Why do typical covalent, simple molecular compounds not conduct electricity?
There are no charged particles to carry charge
