Atoms and Elements Chapter Notes | Chemistry for GCSE/IGCSE - Year 11 PDF Download

 Page 1


Atoms combining
? An element is a substance which only contains one kind of atom
? A compound is made up of multiple elements chemically bonded together
? A mixture contains different substances that are not chemically bonded together
? Chemical change
? When a new substance is formed and the reaction is irreversible
? Signs of chemical change
¦ One or more chemical substances are formed
¦ Energy is taken in or given out, during the reaction
¦ The change is usually difficult to reverse
? If no new chemical is formed, it is known as a physical change
? Ions
? An ion is a charged particle. It is charged because it has an unequal number of protons and
electrons
? If it has charge of 1+ then its a positive ion
? If it has charge of 1- then its a negative ion
? Ionic bonds
? Bonds formed between positive and negative ions is called an ionic bond
? It is formed because of the transfer of electrons from metal to non-metal. Metals get a
positive charge(transfer) and nonmetal get negative ions(acceptance)
? Ionic compound
? A metal reacts with a non-metal to form a ionic compound
? Electrostatic forces of attraction between ions are very strong because they are very
stable compounds
? Properties of ionic compound
? Able to conduct electricity in the molten or aqueous state because of the presence of ions
? They don't conduct electricity in solid state as they do not have free electrons
? Electrons are present in solids
? Ions are present in aqueous, liquid or molten solutions
¦ ? Molten  liquified by heat
¦ ? Aqueous  dissolved in water
? Ionic bonds are soluble in water
Page 2


Atoms combining
? An element is a substance which only contains one kind of atom
? A compound is made up of multiple elements chemically bonded together
? A mixture contains different substances that are not chemically bonded together
? Chemical change
? When a new substance is formed and the reaction is irreversible
? Signs of chemical change
¦ One or more chemical substances are formed
¦ Energy is taken in or given out, during the reaction
¦ The change is usually difficult to reverse
? If no new chemical is formed, it is known as a physical change
? Ions
? An ion is a charged particle. It is charged because it has an unequal number of protons and
electrons
? If it has charge of 1+ then its a positive ion
? If it has charge of 1- then its a negative ion
? Ionic bonds
? Bonds formed between positive and negative ions is called an ionic bond
? It is formed because of the transfer of electrons from metal to non-metal. Metals get a
positive charge(transfer) and nonmetal get negative ions(acceptance)
? Ionic compound
? A metal reacts with a non-metal to form a ionic compound
? Electrostatic forces of attraction between ions are very strong because they are very
stable compounds
? Properties of ionic compound
? Able to conduct electricity in the molten or aqueous state because of the presence of ions
? They don't conduct electricity in solid state as they do not have free electrons
? Electrons are present in solids
? Ions are present in aqueous, liquid or molten solutions
¦ ? Molten  liquified by heat
¦ ? Aqueous  dissolved in water
? Ionic bonds are soluble in water
? Bonding with LiF(Lithium fluoride)
? LiF has a very high melting point as a lot of energy is needed to break the high
electrostatic forces of attraction between the ions
? LiF is soluble in water
? LiF does not conduct electricity in solid state because in solid state, LiF does not contain
free electrons
? It conducts electricity in
aqueous state
Bonding with MgCl2
? Rules for drawing dot and cross diagram
? Always draw the nucleus with the symbol of the element
? Write the electronic configuration
? Don't forget the charges
? Never leave an empty shell
? Draw all the shells(unless specified in question)
? Draw a key of different symbols representing the +ve and -ve ions
? Covalent bonding
? A covalent bond consists of a shared pair of
electrons with electrons being supplied by each
atom, either side of the bond
Page 3


Atoms combining
? An element is a substance which only contains one kind of atom
? A compound is made up of multiple elements chemically bonded together
? A mixture contains different substances that are not chemically bonded together
? Chemical change
? When a new substance is formed and the reaction is irreversible
? Signs of chemical change
¦ One or more chemical substances are formed
¦ Energy is taken in or given out, during the reaction
¦ The change is usually difficult to reverse
? If no new chemical is formed, it is known as a physical change
? Ions
? An ion is a charged particle. It is charged because it has an unequal number of protons and
electrons
? If it has charge of 1+ then its a positive ion
? If it has charge of 1- then its a negative ion
? Ionic bonds
? Bonds formed between positive and negative ions is called an ionic bond
? It is formed because of the transfer of electrons from metal to non-metal. Metals get a
positive charge(transfer) and nonmetal get negative ions(acceptance)
? Ionic compound
? A metal reacts with a non-metal to form a ionic compound
? Electrostatic forces of attraction between ions are very strong because they are very
stable compounds
? Properties of ionic compound
? Able to conduct electricity in the molten or aqueous state because of the presence of ions
? They don't conduct electricity in solid state as they do not have free electrons
? Electrons are present in solids
? Ions are present in aqueous, liquid or molten solutions
¦ ? Molten  liquified by heat
¦ ? Aqueous  dissolved in water
? Ionic bonds are soluble in water
? Bonding with LiF(Lithium fluoride)
? LiF has a very high melting point as a lot of energy is needed to break the high
electrostatic forces of attraction between the ions
? LiF is soluble in water
? LiF does not conduct electricity in solid state because in solid state, LiF does not contain
free electrons
? It conducts electricity in
aqueous state
Bonding with MgCl2
? Rules for drawing dot and cross diagram
? Always draw the nucleus with the symbol of the element
? Write the electronic configuration
? Don't forget the charges
? Never leave an empty shell
? Draw all the shells(unless specified in question)
? Draw a key of different symbols representing the +ve and -ve ions
? Covalent bonding
? A covalent bond consists of a shared pair of
electrons with electrons being supplied by each
atom, either side of the bond
? Properties
¦ No transfer of electrons, electrons are shared
¦ No inner shells, each pair of shared electrons form a bond
¦ Both octet and duplet rules are satisfied and the atoms are stable
? Covalent bonding between the atoms in each molecule is strong. Bonding between individual
molecules is not covalent and is weak
? Covalent bonds don't dissolve in water nor are they soluble
Hydrogen
? Covalent bond
? Represented as H-H
? Linear shape
Methane - CH4
Oxygen
? Double bond(2 lines)
? Bond energy = 408 kJ/M
? Bond energy is the energy required to break
down the bonds
Page 4


Atoms combining
? An element is a substance which only contains one kind of atom
? A compound is made up of multiple elements chemically bonded together
? A mixture contains different substances that are not chemically bonded together
? Chemical change
? When a new substance is formed and the reaction is irreversible
? Signs of chemical change
¦ One or more chemical substances are formed
¦ Energy is taken in or given out, during the reaction
¦ The change is usually difficult to reverse
? If no new chemical is formed, it is known as a physical change
? Ions
? An ion is a charged particle. It is charged because it has an unequal number of protons and
electrons
? If it has charge of 1+ then its a positive ion
? If it has charge of 1- then its a negative ion
? Ionic bonds
? Bonds formed between positive and negative ions is called an ionic bond
? It is formed because of the transfer of electrons from metal to non-metal. Metals get a
positive charge(transfer) and nonmetal get negative ions(acceptance)
? Ionic compound
? A metal reacts with a non-metal to form a ionic compound
? Electrostatic forces of attraction between ions are very strong because they are very
stable compounds
? Properties of ionic compound
? Able to conduct electricity in the molten or aqueous state because of the presence of ions
? They don't conduct electricity in solid state as they do not have free electrons
? Electrons are present in solids
? Ions are present in aqueous, liquid or molten solutions
¦ ? Molten  liquified by heat
¦ ? Aqueous  dissolved in water
? Ionic bonds are soluble in water
? Bonding with LiF(Lithium fluoride)
? LiF has a very high melting point as a lot of energy is needed to break the high
electrostatic forces of attraction between the ions
? LiF is soluble in water
? LiF does not conduct electricity in solid state because in solid state, LiF does not contain
free electrons
? It conducts electricity in
aqueous state
Bonding with MgCl2
? Rules for drawing dot and cross diagram
? Always draw the nucleus with the symbol of the element
? Write the electronic configuration
? Don't forget the charges
? Never leave an empty shell
? Draw all the shells(unless specified in question)
? Draw a key of different symbols representing the +ve and -ve ions
? Covalent bonding
? A covalent bond consists of a shared pair of
electrons with electrons being supplied by each
atom, either side of the bond
? Properties
¦ No transfer of electrons, electrons are shared
¦ No inner shells, each pair of shared electrons form a bond
¦ Both octet and duplet rules are satisfied and the atoms are stable
? Covalent bonding between the atoms in each molecule is strong. Bonding between individual
molecules is not covalent and is weak
? Covalent bonds don't dissolve in water nor are they soluble
Hydrogen
? Covalent bond
? Represented as H-H
? Linear shape
Methane - CH4
Oxygen
? Double bond(2 lines)
? Bond energy = 408 kJ/M
? Bond energy is the energy required to break
down the bonds
Nitrogen
? Triple bond(3 lines)
? Bond energy = 946 kJ/M
? Thus 78% of the atmosphere is nitrogen
? Properties of simple/covalent molecules
? Appearance
¦ In room temperature, simple molecules are gases, liquids or solids with low melting
and boiling points
? Melting point
¦ Very low
¦ Weak attractive forces between molecules means that very less energy is needed
to break their bonds
? Electricity
¦ Don’t conduct electricity because they have no mobile ions or electrons
? Almost opposite to Ionic Bonds
? Giant covalent molecules
? In giant covalent molecules there are many atoms joined together in a regular arrangement
by a very large number of covalent bonds
? Can result in a lattice structure
? General properties of giant covalent molecules
? Melting point
¦ Very high
¦ Structure is made up of a large number of covalent bonds, al of which need to be
broken if atoms are to be separated
? Electrical
¦ Don’t conduct electricity because they have no mobile ions or electrons
? ? ? Giant molecules  macromolecules  covalent networks
Page 5


Atoms combining
? An element is a substance which only contains one kind of atom
? A compound is made up of multiple elements chemically bonded together
? A mixture contains different substances that are not chemically bonded together
? Chemical change
? When a new substance is formed and the reaction is irreversible
? Signs of chemical change
¦ One or more chemical substances are formed
¦ Energy is taken in or given out, during the reaction
¦ The change is usually difficult to reverse
? If no new chemical is formed, it is known as a physical change
? Ions
? An ion is a charged particle. It is charged because it has an unequal number of protons and
electrons
? If it has charge of 1+ then its a positive ion
? If it has charge of 1- then its a negative ion
? Ionic bonds
? Bonds formed between positive and negative ions is called an ionic bond
? It is formed because of the transfer of electrons from metal to non-metal. Metals get a
positive charge(transfer) and nonmetal get negative ions(acceptance)
? Ionic compound
? A metal reacts with a non-metal to form a ionic compound
? Electrostatic forces of attraction between ions are very strong because they are very
stable compounds
? Properties of ionic compound
? Able to conduct electricity in the molten or aqueous state because of the presence of ions
? They don't conduct electricity in solid state as they do not have free electrons
? Electrons are present in solids
? Ions are present in aqueous, liquid or molten solutions
¦ ? Molten  liquified by heat
¦ ? Aqueous  dissolved in water
? Ionic bonds are soluble in water
? Bonding with LiF(Lithium fluoride)
? LiF has a very high melting point as a lot of energy is needed to break the high
electrostatic forces of attraction between the ions
? LiF is soluble in water
? LiF does not conduct electricity in solid state because in solid state, LiF does not contain
free electrons
? It conducts electricity in
aqueous state
Bonding with MgCl2
? Rules for drawing dot and cross diagram
? Always draw the nucleus with the symbol of the element
? Write the electronic configuration
? Don't forget the charges
? Never leave an empty shell
? Draw all the shells(unless specified in question)
? Draw a key of different symbols representing the +ve and -ve ions
? Covalent bonding
? A covalent bond consists of a shared pair of
electrons with electrons being supplied by each
atom, either side of the bond
? Properties
¦ No transfer of electrons, electrons are shared
¦ No inner shells, each pair of shared electrons form a bond
¦ Both octet and duplet rules are satisfied and the atoms are stable
? Covalent bonding between the atoms in each molecule is strong. Bonding between individual
molecules is not covalent and is weak
? Covalent bonds don't dissolve in water nor are they soluble
Hydrogen
? Covalent bond
? Represented as H-H
? Linear shape
Methane - CH4
Oxygen
? Double bond(2 lines)
? Bond energy = 408 kJ/M
? Bond energy is the energy required to break
down the bonds
Nitrogen
? Triple bond(3 lines)
? Bond energy = 946 kJ/M
? Thus 78% of the atmosphere is nitrogen
? Properties of simple/covalent molecules
? Appearance
¦ In room temperature, simple molecules are gases, liquids or solids with low melting
and boiling points
? Melting point
¦ Very low
¦ Weak attractive forces between molecules means that very less energy is needed
to break their bonds
? Electricity
¦ Don’t conduct electricity because they have no mobile ions or electrons
? Almost opposite to Ionic Bonds
? Giant covalent molecules
? In giant covalent molecules there are many atoms joined together in a regular arrangement
by a very large number of covalent bonds
? Can result in a lattice structure
? General properties of giant covalent molecules
? Melting point
¦ Very high
¦ Structure is made up of a large number of covalent bonds, al of which need to be
broken if atoms are to be separated
? Electrical
¦ Don’t conduct electricity because they have no mobile ions or electrons
? ? ? Giant molecules  macromolecules  covalent networks
Giant covalent molecules
? Diamond
? ? Very high M.P.  many covalent bonds must be broken to separate atoms
? ? Very strong  Each carbon atom is joined to 4 others in a rigid structure. Coordination no.
=  4(number of atoms, molecules, ions bonded to it)
? ? Non-conductor of electricity  all four carbon atoms are used for bonding
? Tetrahedral shape
? All electrons are bonded
? No free electrons
? Does not conduct electricity
? Graphite
? Hexagonal shaped
? Are connected by weak Van Der Waals forces (connect the 2 layers)
? ? Melting point is very high  many covalent bonds must be broken to separate atoms
? ? Strength is sod each carbon is joined to 3 others in layered structure
? Coordination no. = 3
? Nanoscience
? Refers to the science of structures that are 1- 100nm in size
? Nanoparticles
? Show different properties to the same materials in bulk and have a high surface area to
volume ratio
? Fullerenes
? Although they are not officially classed as giant molecules, fullerenes are made from
carbon atoms joined together to make tubes and cages
? Nanotubes
? They are fullerenes where hexagonal sheets of carbon atoms have rolled into a tube
? Properties of fullerenes
? ? Very strong  useful where lightness and strength are needed (tennis racket frames)
? ? Conductors of electricity  used as semiconductors, electrical circuits
? ? Tubular structures  used to transport a drug into the body
? Buckminster fullerene
? A fullerene where the carbon dioxide are arranged in a ball shaped molecule
? ? C60  60 carbon atoms are arranged in a ball in rings of 5 and 6