C2 - Atoms, elements and compounds Flashcards
Atoms definition
The smallest particle of an element that can take part in a chemical reaction (e.g oxygen)
Compound definition
2 or more elements chemically combinded and can not be separated by physical means e.g. water, hydrochloric acid
Mixtures definition
2 or more elements physically combined which can be separated by physical means e.g. air
Atomic number
The number of protons present in the nucleus (note: number of electrons and number of protons is same)
Mass number
Sum of all protons and neutrons
2 types of ions:
Cations –> positively charged ions (it has more protons than electrons)
Anions –> negatively charged ions (it has more electrons than protons)
Valency definition
The number of electrons an atom gains or loses to become stable
Radical definition
A group of atoms with a net charge of positive or negative
Sulphate (radical) symbol and valency
SO₄²⁻, valency 2
Hydroxide (radical) symbol and valency
OH⁻, valency 1
Nitrate (radical) symbol and valency
NO₃⁻, valency 1
Carbonate (radical) symbol and valency
CO₃²⁻, valency 2
Phosphate (radical) symbol and valency
PO₄³⁻, valency 3
Bond definition
A chemical interaction between atoms
Ionic bond
Giant ionic structure, between a metal and non-metal. The metal donates and the non-metal recieves
Covalent bond
Between 2 non-metals. They both share electrons (each one gives an equal amount which is then shared)
Metallic bond
Metallic structure, between 2 metals [FINISH ANSWER]
What are the 2 types of covalent bonds?
1) Simple molecular structure
2) Giant covalent structure
Simple molecular structures properties (3)
- They exist as molecules and not ions or atoms. The molecules are held by weak Van Der Whaals force
- They have low melting and boiling points. The molecules are held together by weak intermolecular forces, so a small amount of energy is required to break the bond
- They are poor conductors of heat and electricity because they exist as molecules?
Giant covalent structures properties (1)
- Compounds have high melting and boiling points because of the strong covalent bonds between atoms in the giant network e.g. diamond, graphite
Diamond
In diamond, each carbon shares electrons with four other carbon atoms forming four single bonds. The structure of diamond has strong covalent bonds throughout.
Graphite
Graphite has a layer structure. The layers are held together by weak forces. Each carbon atom in graphite is bonded to 3 other carbon atoms. Because of this, carbon can conduct electricity (carbon has a valency of 4, so it has one carbon atom remaining unbonded). It is also a lubricant because it is made up of layers which slide over each other.
Properties of ionic compounds (3)
1) Good conductors of electricity in molten state or when dissolved in water –> because they exist as ions and ions conduct electricity in solid state, the ions are fixed
2) High melting and boiling points –> because of strong ionic bonds
3) Soluable in water –> because they are polar (having charges [WHAT THE FUCK IS THIS?])
Metallic bond explanation
It is an electrostatic attraction between the positive ions in a giant metallic lattice and a sea of delocalised electrons. Metals are good conductors because they have free/delocalised electrons within the metallic structure.
