Chemistry Vocabulary
• Element: Elements are chemically the simplest substances and hence cannot be broken down further using chemical methods. Elements can only be changed into other elements using nuclear methods.
• Atom: An atom is the defining structure of an element, which cannot be broken by any chemical means.
• A chemical reaction: A reaction or chemical reaction is a chemical change which forms new substances.
• Ex: OH + H H2O (reactant) (product)
• Compound: A substance formed by the reaction of two or more chemical elements.
• Molecule: a molecule refers to two or more atoms which have chemically combined to form a single species.
The structure of the atom
ELECTRON – negative,
mass nearly nothingPROTON –
positive, same mass as neutron
(“1”)
NEUTRON – neutral,
same mass as proton
(“1”)
The Ancient Greeks used to believe that everything was made up of very small
particles. I did some experiments in 1808 that proved this and called these particles
ATOMS:
Dalton
Mass and atomic numberParticle Relative Mass Relative Charge
Proton 1 1
Neutron 1 0
Electron 0 -1
MASS NUMBER = number of protons + number of neutrons
SYMBOL
PROTON NUMBER = number of protons (obviously)
The Atom Oxygen
Protons
Neutrons
Electrons
Oxygen has eight electrons, eight protons and eight neutrons.
The Atom Sodium
Protons
Neutrons
Electrons
Sodium has eleven electrons, eleven protons and twelve neutrons.
Mendeleev
Periodic tableThe periodic table arranges all the elements in groups according to their properties.
Horizontal rows are called PERIODS
Vertical columns are called GROUPS
H He
Li Be B C N O F Ne
NaMg
Al Si P S Cl Ar
K Ca Fe NiCu
Zn Br Kr
Ag I Xe
PtAu
Hg
The Periodic TableFact 1: Elements in the same group have the same number of electrons in the outer
shell (this correspond to their group number)
E.g. all group 1 metals have __ electron in their outer shell
These elements have __ electrons in their outer shell
These elements have __ electrons in their outer shells
H He
Li Be B C N O F Ne
NaMg
Al Si P S Cl Ar
K Ca Fe NiCu
Zn Br Kr
Ag I Xe
PtAu
Hg
The Periodic TableFact 2: As you move down through the periods an extra electron shell is added:
E.g. Lithium has 3 electron in the configuration 2,1
Potassium has 19 electrons in the configuration __,__,__
Sodium has 11 electrons in the configuration 2,8,1
H He
Li Be B C N O F Ne
NaMg
Al Si P S Cl Ar
K Ca Fe NiCu
Zn Br Kr
Ag I Xe
PtAu
Hg
The Periodic TableFact 3: Most of the elements are metals:
These elements are metals
This line divides metals from non-metals
These elements are non-metals
H He
Li Be B C N O F Ne
NaMg
Al Si P S Cl Ar
K Ca Fe NiCu
Zn Br Kr
Ag I Xe
PtAu
Hg
The Periodic TableFact 4: (Most important) All of the elements in the same group have similar PROPERTIES. This is how I thought of the
periodic table in the first place. This is called PERIODICITY.
E.g. consider the group 1 metals. They all:
1) Are soft
2) Can be easily cut with a knife
3) React with water
How shells fill
• The first electron shell can only hold a maximum of two electrons.
• The second electron shell can hold a maximum of eight electrons.
• The third electron shell can also hold a maximum of eight electrons.
• The fourth electron shell can also hold eight electrons.
Electron structure
Consider an atom of
Potassium:
Potassium has 19 electrons. These are arranged in shells…
Nucleus
The inner shell has __ electrons
The next shell has __ electrons
The next shell has __ electrons
The next shell has the remaining __ electron
Electron structure
= 2,8,8,1
Forming BondsAtoms can bond to each other and make molecules.These bonds are what hold molecules together.Bonds form when atoms either give away or share electrons.
Ionic Bonds
Ionic bonds form when one atom takes an electron from another atom.Stable atoms are atoms that have full valence shells.Unstable atoms are atoms that do not have filled valence shells
Water
• Water is covalently bonded.• It is more positive on one side than another.• This makes it charged and can pull apart
other charged particles.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
pH
• When something is an acid it contains a lot of H+(ions)
• When something is a base it contains a lot of OH-(ions)
• When it is neutral it contains the same amount of H ions and Oh ions.