Chemistry

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.

Atomic Structure

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

The Atom

Nucleus Electron

Shell or Orbit

The Atom Hydrogen

Proton Electron

Hydrogen has one proton, one electron and NO neutrons

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 Carbon

Protons

Neutrons

Electrons

Carbon has six electrons, six protons and six neutrons.

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.

How many protons, neutrons and electrons?

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.

Covalent Bonds

Covalent bonds are bonds in which atoms 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

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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.

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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.

pH Scale

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