Chemical bonding, structure and properties Flashcards
What is an element?
A substance made from only one type of atom - cannot be decomposed into simpler substances by chemical means
What is a compound?
-A substance made from different elements bonded together
What is a mixture?
Mixtures contain more than one element or compound
Why do elements react?
To form compounds which have the electron configuration of a noble gas i.e. full outer shell
How are ionic bonds formed?
- When a metal and non metal reacts
- The metal atom loses electrons whilst the non metal gains these electrons- transfer electrons
- Creates positively and negatively charged ions that are ATTRACTED
What is ionic bonding?
An electrostatic attraction between oppositely charged ions
Describe the structure of ions bonding
-Giant Ionic Lattice:
(millions of particles in a regular repeating arrangement- bonding is multi directional
What is covalent bonding?
shared pair of electrons usually between 2 non-metals
Describe the structure of compounds with covalent bonds
In SIMPLE MOLECULAR:
-strong covalent bond between atoms, however, the molecules have weak intermolecular forces between them
E.g: water, ammonia, methane)
in GIANT STRUCTURES:
-made up of a single, giant lattice- continuous network of atoms linked by covalent bonds
E.g: Diamond, graphite, silicon dioxide
How does ionic bonding affect the boiling/ melting points in ionic compounds?
have HIGH mp’s/bp’s:
-Because of giant lattice of ions with strong electrostatic forces between oppositely charged ions
How do simple molecular structures affect the boiling/ melting points in compounds with covalent bonds
have LOW mp’s/bp’s:
-Because of weak intermolecular forces between molecules
How do giant structures affect the boiling/ melting points in compounds with covalent bonds
have VERY HIGH mp’s/bp’s:
-Because of many strong covalent bonds in macro molecular structure- takes a lot of energy to break the many strong bonds
How is the conductivity of ionic compounds?
when SOLID:
-do not conduct electricity because the ions cannot move around freely
when MOLTEN:
-does conduct electricity because the ions can move and carry the charge
How is the conductivity in compounds with covalent bonding?
GRAPHITE conducts electricity because it contains delocalised electrons that can move along the layers-
However, MOST GIANT SUBSTANCES do not conduct electricity- do not contain delocalised electrons
Why is graphite soft, but other giant structures like diamond/ silicon dioxide are very hard?
Diamond and silicon dioxide are very hard due to the rigid network of atoms linked by covalent bonds- graphite is soft due to the layers of covalently bonded atoms are not bonded to each other; can slide over each other
What is metallic bonding?
An electrostatic force of attraction between the metal positive ions and the delocalised electrons
How does metallic bonding occur?
In metals, the outer shell electrons are delocalised and can move throughout the metal
Describe the structure of compounds with metallic bonding
Giant metallic lattice of positively charge ions surrounded by delocalised electrons
How does metallic bonding affect the melting points of metals?
Most metals have high melting points because there is a strong overall attraction between the positive metal ions and the negative delocalised electron cloud
Why can metals conduct electricity?
Because the outer shell electrons are delocalised and can carry charge through the metal.
What makes metals malleable (can be hammered into shape)?
Because the metal ions can move relative to each other while maintaining the metallic bonding- layers can slide past one another
What bonds are affected from molecular substances melting or boiling
When molecular substances melt or biol, it is the weak intermolecular forces between molecules that are overcome- The covalent bonds within the molecules DO NOT BREAK
What is the symbol for the compound ion of hydrogen?
H+
What is the symbol for the compound ion of ammonium?
NH4+
