chemistry- history of the periodic table/ atom

How the periodic table is arranged

-there are 8 groups \n -elements who are in the same group have the same group have the same number of atomic shells horizontally \n -hydrogen is a billy no mates because it only has an atomic number of 1 and only 1 electron \n -put in order of protons \n -groups are organised in similar chemical propitiates \n -named group 0 because there are full outer shells meaning it needs no more electrons to be full \n -group 4 metals are made up of transition metals \n -4th shell

Johanne Dobereine(1817)

Came up with the 'Law of triads '

Law of Triads

put elements into groups of 3 where appearance and reactions of the elements were similar

John Newlands (1864)

Came up with the 'Law of 8'.

Law of 8

noticed that if you arranged the elements in order of their atomic mass then each element is similar to the one element places on. BUT some elements were placed in the wrong group and some were doubled-up

Dmitri Mendeleev (1869)

He grouped the 63 known elements with similar properties into columns (called groups) forming the early periodic table.

Iodine and Tellurium

Iodine and Tellurium he changed the order based on atomic weight and properties he thought reactivity was more important than mass

gaps

He left these for undiscovered elements and predicted where their places might be.

Predicted elements

These elements were later discovered and Mendeleev's predictions were found to be right and the gaps were filled

Periods

Horizontal rows on the periodic table

Elements in the same period

have the same number of electron shells

Groups

Vertical columns on the periodic table

Elements in the same groups have

the same number of electrons in their outer shell

similar chemical properties

all the elements in group 1 have

one electron on their outer shell and react in a similar way with water.

Elements in the same group also have

similar physical properties.

The word periodic in the name of the periodic table refers to

to this repeating pattern of similar properties

Group 1 elements are called

alkali metals

Group 2 elements are called

Alkaline metals

Group 7 elements are called

Halogens

there is only allowed

2 electrons in the 1st shell

you can only have

8 electrons in the other shells

In order to get a full outer shell do Group 1 elements need to

loose an electron

how the size of atoms changes as you go down a group

-the atoms get larger as you go down the group

-the outer electron gets further from the nucleus as you go down the group

How does the melting point change as you go down Group 1?

the melting point gets lower

are group 7 metals or non-metals

non metals

What is the boiling point pattern going down Group 7?

the boiling point increases

Which halogens are gases at room temperature (25 °C)?

bromine and iodine

Another name for noble gases is inert gases. What does inert mean?

non reactive

The Group 7 elements are called

halogens

Before the discovery of protons, neutrons and electrons, scientists attempted to classify the elements by arranging them in order of

there atomic weights

Elements that react to form

positive ions are metals.

Elements that do not react form

positive ions are non-metals.

proprieties of the transition elements

elements have ions with different charges, form coloured compounds and are useful as catalysts.