2. Atoms, elements and compounds Flashcards
2.1 Elements, compounds and mixtures 2.2 Atomic structure and the Periodic Table 2.3 Isotopes 2.4 Ions and ionic bonds 2.5 Simple molecules and covalent bonds 2.6 Giant covalent structures 2.7 Metallic bonding
Ion
A positively or negatively charged particle formed by the loss or gain of electrons.
Atom
A neutral particle composed of protons, neutrons and electrons.
Electron
Subatomic negatively charged particles that orbit the nucleus of an atom. Mass = 0, Electrons = Atomic Number 2.8.8.2
Neutrons
Subatomic particles with no charge. Found in the nucleus. Mass = 1, Neutrons = Atomic mass - Atomic number.
Element
A chemical substance that cannot be broken down into simpler substances. It is composed of one type of atom only.
Anion
A negatively charged ion.
Cation
A positively charged ion.
Period
Row in the periodic table. Period number = Number of occupied electron shells.
Mixture
Two or more chemical substances found together but no chemically bonded.
Group
Column in the periodic table. Group number = Number of electrons in the outer shell (exception helium)
Protons
Positively charged subatomic particle found in the nucleus of an atom. Mass = 1, Protons = Atomic number.
Covalent bond
A force of attraction between shared pairs of electrons and the nuclei of two atoms.
Organic compound
A substance consisting of carbon and one or more other elements, joined together by covalent bonds.
Natural Gas
Gas that people burn for energy (Methane).
Alkane
An organic compound containing only single C–C and C–H bonds.
Alkene
An organic compound containing one or more C=C double bonds.
Alcohol
An organic compound that contains an OH functional group.
but
C₄
meth
C
eth
C₂
prop
C₃
ane
single bonds + alkane
ene
double bonds + alkene
anol
OH + alcohol
Alkene (General Formula)
CₙH₂ₙ
Alcohol (General Formula)
CₙH₂ₙ₊₁OH
Alkane (General Formula)
CₙH₂ₙ₊₂
Triple Bond
A covalent bond in which three pairs of electrons are shared.
Double Bond
A covalent bond in which two pairs of electrons are shared.
Single Bond
A covalent bond in which one pair of electrons are shared.
Macromolecule
A giant molecule created by atoms covalently bonded to one another.
Allotropes
Alternative forms of an elemental substance. For example, diamond and graphite are allotropes of carbon.
Delocalised
Electrons that are not associated with a particular atom.
Intermolecular forces
The weak force of attraction that holds molecules close together
Volatility
The property of a material describing how easily it vaporises (evaporates).
Covalent Molecules (Properties)
- They have weak intermolecular forces
- Extremely volatile (bonds break easily)
- Often soluble in water or other solvents (eg. alcohol)
- Poor conductors of electricity in any form
- Low melting points
Ionic compounds (Properties)
- Strong ionic bonds.
- High melting points / Not volatile (Difficult to break bonds)
- Do not conduct when solid.
- Conduct electricity when in solution (for a while)
Diamond
- Each carbon atom makes 4 covalent bonds
- Regular arrangement
- High melting point - bc strong covalent bonds require ~ 4000 celsius to break.
- Hardest natural substance - 10 on the mohs scale thus used in large industrial drills.
Silicon Dioxide
- Qaurtz/Sand
- Each silicon atom makes 4 bonds with one oxyen atom
- 3D lattice of atoms
- Very similar structure to diamond
- Very high melting point - bc of strong covalent bonds require lots of energy to break
Graphite
- Each carbon atom makes 3 strong covalent bonds with other carbon atoms
- Creates sheets of hexagonally arranged carbon atoms - one sheet is called graphene
- Weak intermolecular force between sheets holding them together - sheets can slide on each other (forces between sheets break easily) - Graphite dust used as lubricant in machines between gears etc.
- Good conductor - used to make electrodes - bc 4th valence electron is free (delocalised) and carries current around the layer.
