C4

The Periodic Table is a table which arranges the chemical elements

• The chemicals are arranged in order of proton number (also known as the atomic number, and shown below each element)
• There are repeating patterns in the element's properties
• The vertical columns are called groups (each collum has a group number)
• The elements in a group have similar properties
• The horizontal rows are called periods
• The elements to the left of a stepped line between aluminum and silicon, germanium and arsenic, and so on, are metals. The elements to the right of this stepped line are non-metals

How was the Periodic Table created?

Dobereiner noticed there were several groups of 3 elements with similar properties. 

Newlands arranged the elements in order of relative atomic mass. Every eighth element had similar properties. His pattern only worked for the first 16 elements

Mendeleev showed there were patterns in the properties of all the elements when arranged in relative atomic mass order. He made a sensible pattern by leaving gaps for missing elements. He predicted the missing elements' properties. Later, scientists discovered these elements.

The elements in Group 1 of the Periodic Table are called the Alkali Metals.

The Alkali Metals include the elements Lithium (Li), Sodium (Na), and Potassium (K). The Alkali Metals; 

• have low densities, so they float on water
• have low melting and boiling points
• are shiny when freshly cut
• quickly tarnish in damp air because they react with oxygen

Alkali Metals react with water to make Hydrogen and an Alkaline Solution.

Going down the group, the reactions get more vigorous (strong)

Alkali Metals also react vigorously with Chlorine Gas to make Chlorides. The Chlorides are colourless crystalline solids.

The elements in Group 7 of the Periodic Table are called Halogens. They include Chlorine (Cl), Bromine (Br), and Iodine (I)

The Halogens are diatomic - this means they exist as molecules, each with a pair of atoms. Chlorine molecules have the formula Cl2, Bromine Br2, and Iodine I2.

Going down the Group 7, the elements become less Reactive. For example, Hot iron glows brightly in Chlorine Gas, It glows less brightly in Bromine, and hardly at all in Iodine.

Halogens have low melting and boiling points. This is a typical property of non-metals.

Atoms are not the smallest particles of matter. Atoms are made up of even smaller, subatomic particles called protons, neutrons and electrons.

Protons, neutrons, and electrons

At the center of every atom is a nucleus containing protons and neutrons. All atoms of the same element have the same number of protons. This number is used to arrange the elements in the Periodic Table, beginning with Hydrogen, which has just one proton.

Electrons are contained in shells around the nucleus. The total number of electrons is always the same as the number of protons in the nucleus.

Flame Colours;

When the atoms of some metals are heated, they give off coloured light. The colour given off by each metal is different and can be used to identify them.

If you hold any lithium compound in a Bunsen flame at the end of a Platinum wire, you see a red flame. The compounds of other elements make different colours.

When the light from the flame goes through a prism, it makes a line spectrum.

Every element has a different spectrum, Chemists have studied these spectra and so discovered new elements, for example, Helium.

The number of protons in the atom of an element determines its place in the Periodic Table. The number of electrons in an atom is the same as the number of protons. These electrons are arranged in shells or 'energy levels' around the nucleus. The arrangement of electrons determines the chemical properties of an element.

E.g, Lithium

the black dot represents the nucleus. Lithium atoms have 3 electrons. Lithium is in Group 1 of the Periodic Table.

E.g, Calcium

calcium atoms have 20 electrons. Calcium is in Group 2 of the Periodic Table.