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
