Test Flashcards
Define a compound
A pure substance that can be simplified. They are made up of two or more DIFFERENT elements chemically combined in a fixed ratio
Define a molecule
A molecule is 2 atoms (can be the same or different) that are chemically bonded together
Define a mixture
A mixture is impure and consists substances that are not chemically joined and not in a fixed ratio
Name the 7 properties of metals
- lustrous fresh surface
- good conductors of electricity
- good conductors of heat
- malleable
- ductile
- solid and room temp
- relatively dense
Proton - state where it is found, charge and size
In nucleus (therefore a nucleon) Positive charge Relatively large (1amu)
Neutron- state where it is found, charge and size
In nucleus (therefore a nucleon) Neutral charge Relatively large (1amu)
Electron- state where it is found, charge and size
In orbit in shells outsider of atom Negative charge Relatively small (0amu)
Define a physical change
Physical changes are changes affecting the form of a chemical substance, but not its chemical composition. A change in state, no new substance is made
Define a chemical change
A chemical change occurs when a substance combines with another to form a new substance. They are difficult to reverse. Reactant =products
Characteristics of a physical change
Change in colour, temperature, state, shape and volume
Characteristics of a chemical change
Change in colour, temperature, odor/smell, production of light, bubbles, precipitate
Solid to a liquid
Fusion
Solid to a gas
Sublimation
Gas to solid
Deposition
Gas to liquid
Condensation
Liquid to solid
Solidification
Liquid to gas
Vapourisation
Define an ion
An ion is an atom that has gained or lost on or more electrons.
Name given to a positive ion
Cation
Name given to a negatively charged ion
A ion
The periodic table is a list of elements in order of increasing ________
Atomic numbers
The symbol for atomic number
Z
Symbol for number of neutrons
N
What does the atomic number show?
How many protons and electrons in an atom
Symbol for atomic mass number
A
What is the atomic mass number?
The number of protons and neutrons (number of nucleons)
What is an isotope?
Isotopes are atoms of the same element (same proton number) but with different atomic masses (different neutron number)
What is the density formula?
D= M divided by V
Define the electronic structure
1st shell = 2
2nd shell = 8
For the first 20 elements, the 3rd shell appears to be full with 8 electrons
Name the properties of group 1 elements
All very reactive metals
Known as the alkali metals
They react violently with water e.g sodium
Name the property of group 2 elements
All are reactive metals
Name the properties of group 7 elements
All very reactive
Non-metals
All are found in diatomic molecules
Name the properties of group 8 elements
Are very non reactive
Are caller the noble gases
Have a full Valence shell
Define an ionic bond
Ionic bonds form following a transfer of electronics between atoms resulting in the formation of ions.
They bond with atoms on the opposite side of the periodic table
Define a covalent bond
Covalent bonds form when electrons are shared between atoms. When the atoms both need to gain electrons to complete their valency shells.
Groups in a periodic table refer to
The number of electrons in the valency shell.
E.g. Group 5 have 5 electrons in the outer shell
List the properties of acids
Have a sour taste Change litmus from blue to red Conduct an electric current Corrode most metals React with carbonates Neutralise bases
Name 3 strong acids
Hydrochloride acid, sulfuric acid and nitric acid
Name 3 weak acids
Acetit acid, carbonic acid, Citric acid
List the properties of bases
A bitter taste
Change colour of red litmus to blue
Conduct an electric current
Have a slippery feel
Name some common alkalis (bases)
Sodium hydroxide NaOH
Potassium hydroxide KOH
calcium hydroxide Ca(OH)2
An alkali is any substance that produces ______ in water
OH- ions
an alkali has a ph of
More than 7
A base will ______ an acid
Neutralise
Alkalis are ______ and _______ substances
Alkalis are HARMFUL and CORROSIVE substances
List the properties of an ionic compound
Made up of both + and - ions Solid at room temp Have high melting points Dissolve in water to form aqueous solutions Conduct electricity
Ionic compounds usually form ______ of positive and negative ions rather than individual molecules
Lattices
What is a lattice?
A lattice is an ordered structure of ions held together by the electrostatic attraction between + and - ions
What is a bonding electron
The name given to the shared electron in the covalent compound
Characteristics of covalent compounds are
Low melting points, as the attraction between molecules is weak
Generally do not conduct electricity bc the aren’t made up of ions
insoluble in water
What is a chemical formula
A chemical formula is a set of symbols showing the elements present in the compound and shows their ratio
How is a valency of an element determined?
The Valencia determined by the number of electrons and element wants to gain or lose
Covalent bonds form between elements that are —— on the periodic table
Close together on the right hand side of the periodic table
Mono means
1
Di means
2
Tri means
3
Tetra means
4
Pent means
5
Define an element
A pure substance that cannot be simplified. Are made up of one type of atom only.
Name the 2 liquids in the periodic table
Mercury and bromine
Name the 6 semi metals in the periodic table
Silicon, germanium, arsenic, antimony, selenium and tellurium
Name the 11 gases in the periodic table
Hydrogen, helium, nitrogen, oxygen, fluorine, neon, chlorine, argon, krypton, xenon, radon
Describe the dalton model
Thought atoms were hard indivisible spheres
Describe the Thomson model
Though that the whole atom was + charged, with - electrons embedded in it like a plum pudding
Describe the Rutherford model
He was the first to discover the nucleus, and that electrons orbited around. Only flaw was that the electrons would lose energy and special inwards
Describe bohrs model
Had the same as rutherfords, only that electrons could only exist in specific shells with a certain amount of energy. Also explained why they didn’t special inwards
Describe chadwicks model
Chadwick is the model we use today
He found that the nucleus contained neutrons
Describe aristotles model
Thought that everything was made up of earth, fire, water and air composed of different ratios
What is a binary compound
A compound of 2 elements. The 1st one being the metal involved, the 2nd is the name of the non metal - ending in ide
What is an ionic compound
A compound where ions are held together in a structure by electrostatic forces
What is a covalent compound
Covalent compounds form between 2 or more NON METALS. The atoms share electrons to gain a full outer shell
Metal + oxygen =
Metal oxide
Metal + acid =
Salt + hydrogen
Metal oxide + acid =
Salt + water
Alkali + acid =
Salt + water
Metal carbonate + acid =
Salt + carbon dioxide + water
Very active metal + water =
Metal hydroxide + hydrogen
Define an acid
An acid is a compound containing hydrogen that gives free hydrogen ions in solution
Define a base
A base is a compound that neutralises an acid
Define an alkali
An alkali is a soluble base. They give free hydrogen ions in solutions
Define a salt
A salt is the IONIC compound formed when the hydrogen of an acid is replaced by a metal ion
Chemical reactions that absorb energy are called
Endothermic - temp gets colder
Chemical reactions that produce energy are called
Exothermic - get warmer
Define the term valency
The number of un paired electrons in an atoms outermost shell
What is a polyatomic ion?
An ion containing more than one atom
Define pH
Ph means potential hydrogen. It is a measure of the acidity or alkalinity of a solution
Define diatomic molecule and explain why they form
A diatomic molecule forms via a covalent bond, as both want to gain more stability (full valence shell)
What is a homonuclear diatomic molecule
A homonuclear diatomic molecule is the covalent bond of two SAME elements. Each atom in the molecule has an equal electro negativity
What is a heteronuclear atomic molecule
A heteronuclear diatomic atom consists of 2 DIFFERENT atoms- thus different in electro negativity. They have polar covalent bonds
