Inside AtomsBuilding Blocks of Matter
Matter is the substance that all objects are made of. It may be a solid, liquid, or gas state.
All matter is made of extremely small particles called atoms. They are the building blocks of matter.
Atoms have a central nucleus which contains most of the mass of the atom. In the nucleus there are sub-atomic particles called protons and neutrons.
Flying around the nucleus are particles called electrons.
This table summarises the location and properties of particles found in atoms.
Particle Charge Mass Location Symbolproton positive relatively heavy in nucleus p or neutron neutral same as proton in nucleus n orelectron negative much lighter than a proton outside nucleus e or
Protons in the nucleus repel one another because like charges repel, but a strong force in the nucleus holds the protons and neutrons together.
The mass number of an atom is the number of protons plus the number of neutrons in the nucleus.
Electrons hurtle about the nucleus at very high speeds.
An atom with equal numbers of protons and electrons is said to be neutral or uncharged. The negative charge of the electrons balances the positive charges of the nucleus.
Electron Shells
Electrons do not escape from their orbits because they are attracted to the positively charged nucleus. They move too fast to be pulled into the nucleus though.
Electrons can have different amounts of energy. Those with low energy are found close to the nucleus, while those with higher energy are found further out.
An electron shell is the space around the nucleus that electrons with equal energy are located. Within shell, electrons do not travel in rigid orbits.
Electrons prefer to be in the lowest energy shells, close to the nucleus if possible. As electrons repel one another, only a limited number can fit into each shell.
The innermost shell has only room for two electrons. The second and third shells can fit up to eight electrons each.
[diagram]
Different Types of Atoms
There are over 100 different types of atoms. Each type of atom has its own name, e.g. oxygen atoms. Each atom has its own symbol, e.g. O.
Atoms differ in mass and size. The mass of an atom is affected by the number of protons and neutrons in the nucleus. The size of an atom is affected by the number of electrons surrounding the nucleus.
Each type of atom has a unique number of protons in its nucleus. For example, all oxygen atoms have eight protons in their nuclei.
The number of protons in the nucleus of an atom is called its atomic number. The atomic number of an oxygen atom is eight.
An electrically neutral atom has the same number of electrons as it has protons, A neutral oxygen atom will have eight electrons.
The electrons in the outer shell of an atom are called its valence electrons. Oxygen has six valence electrons in its outer shell. The number of valence electrons an atom has affects how it reacts.Chemical Elements and the Periodic Table
A substance made of only one type of atom is called a chemical element. As there are over 100 different types of atoms there are over 100 types of elements.
Chemists arrange elements on the Periodic Table according to the atomic number of their atoms.
[periodic table]
The rows of the periodic table are called periods. There are seven periods in total. The symbols of the eight elements in period 2 are Li, Be, B, C, N, O, F, and Ne.
The columns of the Periodic Table are called groups. There are 18 groups in total. The symbols of the six elements in group 2 are Be, Mg, Ca, Sr, Ba and Ra.
The elements to the left of the diagonal line are the metal elements. The elements to the right of the line are the non-metal elements.
Atom ArrangementsBonding between atomsAtoms are usually found bonded to other atoms. They may be bonded to the same or to different types of atoms.
The atoms may be bonded in small groups called molecules. e.g. the sulfur S8 molecule opposite in which eight sulfur atoms are bonded together in a ring structure.
The atoms may be bonded in fixed arrangements called lattices, which contain huge numbers of atoms. The diagram opposite shows sodium and chlorine atoms bonded together in a lattice.
The atoms in both molecules and lattices are held together by the attraction between opposite electrical charges.Behaviour of AtomsThe behaviour of an atom depends on how full its outermost occupied electron shell is. The first shell can accommodate 2 electrons, the second and third can accommodate up to 8 each. The outermost occupied shell is called the valence shell.
Atoms with full valence shells (e.g. helium, neon and argon) are stable and do not react with other atoms.
Atoms with partially filled outer electron shells tend to be unstable and reactive. They can become stable by taking, losing, or sharing electrons to end up with full outer shells.
Metal atoms: Have few valence electrons and their nuclei weakly attract those electrons.
Can lose electrons to stronger non-metal atoms.
Do not share electrons with other metal atoms.
Become stable once there are left with filled inner electron shells.
Such as sodium atoms with one electron in their outer shells, will lose it leaving filled inner shells.
Non-metal atoms:
Have nearly filled valence shells and their nuclei strongly attract electrons.
Can pull electrons off weaker metal atoms.
Share electrons with other non-metal atoms.
Become stable once their valence electron shell is full.
Such as chlorine atoms with seven electrons in their outer shells, will gain electrons resulting in full valence shells.Elements and CompoundsAn element is a substance made of one type of atom only. The atoms may occur singly (e.g. helium atoms), or they may be bonded in molecules (e.g. oxygen atoms in O2), or bonded in a lattice made of millions of atoms (e.g. carbon atoms in diamond).
A compound is a substance in which different types of atoms are bonded. The atoms may be bonded in molecules (e.g. hydrogen and oxygen atoms in water H2O), or they may be bonded in a lattice (e.g. sodium and chlorine atoms in table salt NaCl).MoleculesA molecule is a group of atoms bonded together because they share electrons.
Each molecule is made of a definite number of of atoms, for example phosphorus P4 molecules are always made of four phosphorus atoms.
Each atom in a molecule shares some of its electrons with with its immediate neighbours.
Molecular elements occur when identical atoms share electrons, for example, H atoms in hydrogen H2 molecules. [image] (Balls represent atoms, and sticks bonds).
Molecular compounds occur when non-identical atoms share electrons, for example, water H2O is a molecular compound. The central oxygen atom shares electrons with the two hydrogen atoms.
When a pair of atoms share electrons, the positive nuclei attract the shared negative electrons flying around them. This attraction is called a covalent bond.
Some important molecular compounds are:nitrogen dioxide NO2carbon monoxide COcarbon dioxide CO2water H2Osulfur dioxide SO2ammonia NH3Simple IonsAn uncharged (neutral) atom has the same number of electrons as protons. As there are equal numbers of negative and positive charges, there is no overall charge on the atom.
If an atom gains or loses electrons, the negative and positive charges no longer balance - the atom has become charged. A charged atom is called an ion.
If an atom takes electrons from another to gain a full outer shell, it will now have more negative charge than positive. The atom has become a negatively charged ion.
If an atom loses electrons to another in order to be left with full inner shells, it will now have more positive charge than negative. The atom becomes a positively charged ion.
Ionic CompoundsWhen electrons are transferred between atoms, oppositely charged ions are formed.
The positive and negative ions are attracted to each other. Each negative ion becomes surrounded by positive ions and vice versa. The fixed arrangement is called a lattice.
The attraction between oppositely charged ions holds them together in a lattice. This type of bonding is called ionic bonding.
Ionic compounds are substances whose atoms are held together by ionic bonds. An example of an ionic compound is sodium chloride (NaCl).More Complicated IonsUsually molecules have no overall charge, but some may have extra or insufficient electrons. These charged molecules are also called ions. The charge is spread out over the whole group of atoms.
Some important molecular ions are:hydroxide ion OH-nitrate ion NO3-carbonate ion CO32-sulfate ion SO42-bicarbonate ion HCO3-ammonium ion NH4+Reaction RatesChemical ReactionsReactants and ProductsReaction RatesFactors which Affect the Rate of a ReactionConcentrationSurface AreaTemperatureCatalystsA Chemical ProcessChemical ProcessesAnalysing a Chemical ProcessProperties and Uses of the Chemical ProductRaw MaterialsSiting of the Plant
Matter is the substance that all objects are made of. It may be a solid, liquid, or gas state.
All matter is made of extremely small particles called atoms. They are the building blocks of matter.
Atoms have a central nucleus which contains most of the mass of the atom. In the nucleus there are sub-atomic particles called protons and neutrons.
Flying around the nucleus are particles called electrons.
This table summarises the location and properties of particles found in atoms.
Particle Charge Mass Location Symbolproton positive relatively heavy in nucleus p or neutron neutral same as proton in nucleus n orelectron negative much lighter than a proton outside nucleus e or
Protons in the nucleus repel one another because like charges repel, but a strong force in the nucleus holds the protons and neutrons together.
The mass number of an atom is the number of protons plus the number of neutrons in the nucleus.
Electrons hurtle about the nucleus at very high speeds.
An atom with equal numbers of protons and electrons is said to be neutral or uncharged. The negative charge of the electrons balances the positive charges of the nucleus.
Electron Shells
Electrons do not escape from their orbits because they are attracted to the positively charged nucleus. They move too fast to be pulled into the nucleus though.
Electrons can have different amounts of energy. Those with low energy are found close to the nucleus, while those with higher energy are found further out.
An electron shell is the space around the nucleus that electrons with equal energy are located. Within shell, electrons do not travel in rigid orbits.
Electrons prefer to be in the lowest energy shells, close to the nucleus if possible. As electrons repel one another, only a limited number can fit into each shell.
The innermost shell has only room for two electrons. The second and third shells can fit up to eight electrons each.
[diagram]
Different Types of Atoms
There are over 100 different types of atoms. Each type of atom has its own name, e.g. oxygen atoms. Each atom has its own symbol, e.g. O.
Atoms differ in mass and size. The mass of an atom is affected by the number of protons and neutrons in the nucleus. The size of an atom is affected by the number of electrons surrounding the nucleus.
Each type of atom has a unique number of protons in its nucleus. For example, all oxygen atoms have eight protons in their nuclei.
The number of protons in the nucleus of an atom is called its atomic number. The atomic number of an oxygen atom is eight.
An electrically neutral atom has the same number of electrons as it has protons, A neutral oxygen atom will have eight electrons.
The electrons in the outer shell of an atom are called its valence electrons. Oxygen has six valence electrons in its outer shell. The number of valence electrons an atom has affects how it reacts.Chemical Elements and the Periodic Table
A substance made of only one type of atom is called a chemical element. As there are over 100 different types of atoms there are over 100 types of elements.
Chemists arrange elements on the Periodic Table according to the atomic number of their atoms.
[periodic table]
The rows of the periodic table are called periods. There are seven periods in total. The symbols of the eight elements in period 2 are Li, Be, B, C, N, O, F, and Ne.
The columns of the Periodic Table are called groups. There are 18 groups in total. The symbols of the six elements in group 2 are Be, Mg, Ca, Sr, Ba and Ra.
The elements to the left of the diagonal line are the metal elements. The elements to the right of the line are the non-metal elements.
Atom ArrangementsBonding between atomsAtoms are usually found bonded to other atoms. They may be bonded to the same or to different types of atoms.
The atoms may be bonded in small groups called molecules. e.g. the sulfur S8 molecule opposite in which eight sulfur atoms are bonded together in a ring structure.
The atoms may be bonded in fixed arrangements called lattices, which contain huge numbers of atoms. The diagram opposite shows sodium and chlorine atoms bonded together in a lattice.
The atoms in both molecules and lattices are held together by the attraction between opposite electrical charges.Behaviour of AtomsThe behaviour of an atom depends on how full its outermost occupied electron shell is. The first shell can accommodate 2 electrons, the second and third can accommodate up to 8 each. The outermost occupied shell is called the valence shell.
Atoms with full valence shells (e.g. helium, neon and argon) are stable and do not react with other atoms.
Atoms with partially filled outer electron shells tend to be unstable and reactive. They can become stable by taking, losing, or sharing electrons to end up with full outer shells.
Metal atoms: Have few valence electrons and their nuclei weakly attract those electrons.
Can lose electrons to stronger non-metal atoms.
Do not share electrons with other metal atoms.
Become stable once there are left with filled inner electron shells.
Such as sodium atoms with one electron in their outer shells, will lose it leaving filled inner shells.
Non-metal atoms:
Have nearly filled valence shells and their nuclei strongly attract electrons.
Can pull electrons off weaker metal atoms.
Share electrons with other non-metal atoms.
Become stable once their valence electron shell is full.
Such as chlorine atoms with seven electrons in their outer shells, will gain electrons resulting in full valence shells.Elements and CompoundsAn element is a substance made of one type of atom only. The atoms may occur singly (e.g. helium atoms), or they may be bonded in molecules (e.g. oxygen atoms in O2), or bonded in a lattice made of millions of atoms (e.g. carbon atoms in diamond).
A compound is a substance in which different types of atoms are bonded. The atoms may be bonded in molecules (e.g. hydrogen and oxygen atoms in water H2O), or they may be bonded in a lattice (e.g. sodium and chlorine atoms in table salt NaCl).MoleculesA molecule is a group of atoms bonded together because they share electrons.
Each molecule is made of a definite number of of atoms, for example phosphorus P4 molecules are always made of four phosphorus atoms.
Each atom in a molecule shares some of its electrons with with its immediate neighbours.
Molecular elements occur when identical atoms share electrons, for example, H atoms in hydrogen H2 molecules. [image] (Balls represent atoms, and sticks bonds).
Molecular compounds occur when non-identical atoms share electrons, for example, water H2O is a molecular compound. The central oxygen atom shares electrons with the two hydrogen atoms.
When a pair of atoms share electrons, the positive nuclei attract the shared negative electrons flying around them. This attraction is called a covalent bond.
Some important molecular compounds are:nitrogen dioxide NO2carbon monoxide COcarbon dioxide CO2water H2Osulfur dioxide SO2ammonia NH3Simple IonsAn uncharged (neutral) atom has the same number of electrons as protons. As there are equal numbers of negative and positive charges, there is no overall charge on the atom.
If an atom gains or loses electrons, the negative and positive charges no longer balance - the atom has become charged. A charged atom is called an ion.
If an atom takes electrons from another to gain a full outer shell, it will now have more negative charge than positive. The atom has become a negatively charged ion.
If an atom loses electrons to another in order to be left with full inner shells, it will now have more positive charge than negative. The atom becomes a positively charged ion.
Ionic CompoundsWhen electrons are transferred between atoms, oppositely charged ions are formed.
The positive and negative ions are attracted to each other. Each negative ion becomes surrounded by positive ions and vice versa. The fixed arrangement is called a lattice.
The attraction between oppositely charged ions holds them together in a lattice. This type of bonding is called ionic bonding.
Ionic compounds are substances whose atoms are held together by ionic bonds. An example of an ionic compound is sodium chloride (NaCl).More Complicated IonsUsually molecules have no overall charge, but some may have extra or insufficient electrons. These charged molecules are also called ions. The charge is spread out over the whole group of atoms.
Some important molecular ions are:hydroxide ion OH-nitrate ion NO3-carbonate ion CO32-sulfate ion SO42-bicarbonate ion HCO3-ammonium ion NH4+Reaction RatesChemical ReactionsReactants and ProductsReaction RatesFactors which Affect the Rate of a ReactionConcentrationSurface AreaTemperatureCatalystsA Chemical ProcessChemical ProcessesAnalysing a Chemical ProcessProperties and Uses of the Chemical ProductRaw MaterialsSiting of the Plant