An atom is made up of a
positively charged nucleus surrounded by negatively charged electrons
The atomic number is the number of
protons in an atom of a particular element
The mass number of an atom is
the number of protons and neutrons found in a nucleus
What is the mass and atomic number of sodium
Mass number = 23
Atomic number = 11
What sub atomic particles make up the nucleus
protons and neutrons
Difference between physical and chemical changes
Physical changes change the appearance of a substance and not the chemical composition whilst in a chemical change one or more new substances are produced.
What experiment shows that some chemical changes can be reversed
Hydrated blue copper sulfate crystal test
When heated a white powder will form (anhydrous copper sulfate) and water is lost as steam. If water is added it turns blue.
What is the relative mass of protons, neutrons and electrons
proton = 1 neutron = 1 electron = 1/2000
Another name for mass and atomic number
nucleon number (for mass) and proton number (for atomic)
Hydrogen has a proton and electron but no
neutron
In an atom the number of protons is equal to the
number of electrons
In a periodic table the elements are arranged via
their atomic number
Atoms have no
overall charge
When an atom becomes charged due to losing or gaining electrons it is called an
ion
If atoms lose one or more electrons in outer shell its called a
positive ion
If an atom gains one or more electron in outer shell its called a
negative ion
What is an isotope
A same element atom with same number of protons but different number of neutrons
Isotopes have the same properties as their regular atoms because
they have the same number of electrons in the outer shell
A nuclide is a
type of isotope that is characterized due to its distinct specific nucleus
Electrons have fixed positions in atoms called
electron shells
What is the electron configuration of an atom
2 electrons max on the first shell
then it’s 8 max on the next shell after that.
The closer a shell is to the nucleus of an atom
the lower its energy level is
What is the electron configuration of an atom of sodium
11 electrons in sodium so
2,8,1
What is an ionic bond between
a metal (+) and a non-metal (-)
Both metals and non-metals try to achieve a
complete outer electron shell
Properties of non-metals
Poor conductors of electricity Low melting and boiling points Dull Brittle Poor conductors of heat
Ionic bonding involves the
attraction between two oppositely charged ions to achieve a full outer shell of electrons
What are the 3 ways atoms can be chemically bonded
Ionic bonding, covalent bonding and metallic bonding
Covalent bonding involves bonding between
two non-metals to share 1 or more pairs of electrons
Metallic bonding involves attraction between
positive charged metal ions and delocalized negatively charged electrons.
What is an ionic compound
when millions of ions are held together by electrostatic forces between oppositely charged ions in the form of an ionic lattice
Properties of ionic compounds
Cannot conduct electricity in solid form as the ions are fixed and there are no free electrons When turned molten or dissolved in water ions are free and the electrons become delocalized allowing energy flow High MP and BP because a lot of energy required to break the ionic bonds in each ion Are hard (due to strong bonds) and brittle
Ionic compounds are structured in
alternating positive and negative ions in the form of a giant lattice structure
A covalent bond is the result of an
attraction between bonding pairs of electrons and the nuclei of an atom involved
When atoms covalently bond they become
molecules
Small covalent molecules are held by
strong covalent bonds
The forces between the covalent molecules are
weak intermolecular forces
Properties of small covalent molecules
Low BP and MP due to weak intermolecular forces
Cannot conduct electricity due to no free electron
Often gases and liquids at room temperature
Bigger molecules in small covalent molecules have
more intermolecular forces so as you go down the group 7 BP and MP gets bigger
What is an example of a double covalent bond
oxygen as they share 2 pairs of electrons (O2 = O2)
What is the display formula for covalent bond of Cl2
Cl - Cl
How many types of covalent bonds are there
3
Single double and triple bonds
Ionic compound features
Volatility: Low
State at room temp: Solid
Solubility in water: High
Electrical conductivity: Low (ions not free)
Electrical conductivity in solution: High (ions are free)
Covalent bond features
Volatility: High
State at room temp: Usually liquid or gas
Solubility in water: Low
Electrical conductivity: Low (no charge)
Electrical conductivity in solution: Low (no charge)
What are giant covalent structures
Huge number of non-metal atoms and in regular repeating lattices
3 examples of giant covalent structures
Diamond, graphite and silicon dioxide
Properties of giant covalent bonds
One single molecule
High BP and MP because loads of energy required to break every individual strong bond
Don’t conduct electricity even when molten (except graphite)
What are allotropes
Different forms or structures of the same element i.e Allotropes of carbon are diamond, fullerenes and graphite
Properties of graphite
Each carbon atom is bonded to 3 other carbon atoms
They are hexagonal shape and within layers held by weak intramolecular forces.
Layers are soft so slide over each other
Graphite is soft
Used as a pencil and is a lubricant
Has free electrons so conducts heat and electricity
Properties of diamond
Very hard (used for cutting tools or to cut materials)
Each carbon atom is bonded to 4 other carbon atoms
Has high melting point
Does not conduct electricity as no free electrons
A solid metal consist of
Giant structure of atoms in a regular pattern
How is a metal held in a regular structure
The metal atoms give up its electrons to share with other metal atoms. It forms a sea of delocalized electrons.
The metal atoms become positively charged as they lost electrons and are electrostatically attracted to the negatively charged electrons which holds the metal together in a regular pattern
Why are alloys harder to break than pure metals
Since alloys consist of two or more different metallic elements the atoms are different sizes which disrupts the regular pattern and makes it harder to slide over the layers.
What are the layers in graphite called
graphene
Graphene can be shaped into tubes and spheres called
fullerenes
Use of fullerenes
Transport drugs
Industrial catalyst
Nanotubes