Chemistry Flashcards
Definition of the following:
Element
Atom
Compound
Mixture
Substance made up of one type of atom
The smallest part of an element to exits
A substance made up of atoms of two or more elements chemically joined together with unique chemical properties.
A substance made up of atoms of two or more elements not chemically combined
Isotopes
Atoms with the same atomic number but different mass number, same number of protons, different number of neutrons
Relative atomic mass
A = (% abundance x isotopic mass)(% abundance x isotopic mass) / 100
History of atoms
Democritus 400BC
John Dalton 1803
JJ Thomas plum pudding model
Ernest Rutherford’s nuclear model
Bohr’s Model
Modern day Chadwick (1932)
Gold Foil experiment
Alpha particles fired from the nucleus of a helium atom, probes that an atom is mostly empty space, mass concentrated around the nucleus, which is positively charged.
Relative atomic mass
Relative formula mass
Mass of an atom
Mass of all the atoms in a compound
The mole
Abbreviation used by chemists to mean the relative atomic mass in grams or relative formula mass
The mole
Abbreviation used by chemists to mean the relative atomic mass in grams or relative formula mass
Avogadro’s constant
6.02 x 10(23)
Moles
Mass (g) / Mr
Solid —> gas
Sublimation
Gas —> solid
Deposition
Types of bonds:
Metallic
Covalent
Ionic
• Strong electrostatic forces of attraction between positive metal ions and delocalised electrons
• Two non metals bonded together, sharing 1 or more pairs of electrons
• Strong electrostatic forces of attraction between oppositely charged ions
• Simple molecule structure
• Giant Ionic Lattice structure
• Giant Covalent structure
• Fixed number of atoms joined by covalent bonds
• Large number of atoms/ions arranged in a regular way
• Large number of atoms covalently joined in a regular wat
Why do molecules have low melting and boiling points?
Weak intermolecular forces between atoms are easy to overcome and don’t require a lot of energy to break
Why do giant ionic lattices have high boiling points?
They have strong electrostatic forces of attraction between molecules, which are hard to overcome.
Why don’t simple molecules conduct electricity?
• they don’t contain charged particles or delocalised electrons to be able to carry charge through the structure
Why can ions conduct when liquid?
Because then the ions are free moving particles to be able to carry charge through the structure
Diamond vs Graphite
Bonds per carbon atom
Electrical conductivity
How hard
Melting point
Uses
• 4 bonds per carbon vs 3 bonds per
• Bad because no delocalised electrons (all four used up in covalent bond) vs good because one delocalised electron to carry charge through structure
• hard because rigid network of strong covalent bonds between carbon atoms vs soft due to weak intermolecular forces of attraction between sheets of layers that can slide
• high bc strong covalent bond hard to break and require lots of energy (for both)
• used for cutting tools because it’s hard and high melting point
• used as lubricant (it’s soft) and used for electrodes to conduct electricity
Graphene (4)
• 3 bonds per carbon
• high melting point due to strong covalent bonds
• conducts electricity due to free delocalised electrons to carry charge through structure
• really hard
Fullerene - two types
• Nanotube
• Buckminster fullerene
• both have 3 bonds per carbon
• both conduct electricity well
• Nanotube has high melting point due to strong covalent bond between atoms
• Buckminster had weak intermolecular forces of attraction between atoms that are easy to overcome
• used in electrical devices, drug services and catalyst
What is a catalyst
A substance that speeds up reactions
Giant Metallic Lattice
• conduct electricity
• high melting point (strong electrostatic forces)
• malleable (lates of ions slide over each other)
• alloy is harder as if u mix another metal it disrupts the regular pattern
