C3.1 - Everything in the Specification

Originally, John [blank_start]Newlands[blank_end], and then Dmitri [blank_start]Mendeleev[blank_end], ordered elements by their [blank_start]relative[blank_end] [blank_start]atomic[blank_end] [blank_start]masses[blank_end], because [blank_start]subatomic[blank_end] particles had not been discovered.

Why is it known as the 'periodic' table?

[blank_start]Newlands[blank_end]' attempt at classifying the [blank_start]periodic[blank_end] [blank_start]table[blank_end] was known as the Law of [blank_start]Octaves[blank_end]. He noticed that every [blank_start]eighth[blank_end] element had similar [blank_start]properties[blank_end], and so he listed the elements in rows of [blank_start]seven[blank_end]. These were his '[blank_start]octaves[blank_end]'. However, [blank_start]Newlands[blank_end]' work was criticised by the Chemical Society in 1865, because: - His groups contained elements that didn't have similar [blank_start]properties[blank_end]. - He didn't leave any [blank_start]gaps[blank_end] for [blank_start]new[blank_end] [blank_start]elements[blank_end] to be discovered. - He mixed up m[blank_start]etals[blank_end] and [blank_start]non-metals[blank_end].

[blank_start]Mendeleev[blank_end] improved on [blank_start]Newlands[blank_end]' work in 1869. He arranged the elements in order of [blank_start]atomic[blank_end] [blank_start]mass[blank_end] (like [blank_start]Newlands[blank_end]), but he left [blank_start]gaps[blank_end] in order to keep elements with the same [blank_start]chemical[blank_end] [blank_start]properties[blank_end] in the same vertical [blank_start]column[blank_end]. These [blank_start]gaps[blank_end] meant that he predicted elements such as gallium and germanium.

Scientists only recognised the importance of the periodic table after Newlands' work.

When [blank_start]subatomic[blank_end] [blank_start]particles[blank_end] were discovered in the late [blank_start]19th[blank_end] century, the [blank_start]periodic[blank_end] [blank_start]table[blank_end] was arranged in order of the atomic ([blank_start]proton[blank_end]) number of the elements, and all the elements were placed into [blank_start]groups[blank_end]. The elements can be seen as being arranged by their [blank_start]electronic[blank_end] [blank_start]structure[blank_end].

What property do elements in the same group have?

The [blank_start]positive[blank_end] charge of the [blank_start]nucleus[blank_end] attracts [blank_start]electrons[blank_end] and holds them in place - the further away they are, the [blank_start]weaker[blank_end] the attraction. If there are lots of [blank_start]inner electrons[blank_end], they get in the way of the [blank_start]nuclear[blank_end] charge, further reducing the attraction. This effect is known as '[blank_start]shielding[blank_end]'.

The Group 7 metals get more reactive as you go down the group.

The Group 1 metals get more reactive as you go down the group.

The combination of increased [blank_start]distance[blank_end] and increased [blank_start]shielding[blank_end] means that an electron in a [blank_start]higher[blank_end] energy level is [blank_start]lost[blank_end] [blank_start]more[blank_end] easily, as there is less attraction from the [blank_start]nucleus[blank_end]. Thus, Group [blank_start]1[blank_end] metals are [blank_start]more[blank_end] reactive as you go down the group. The combination of increased [blank_start]distance[blank_end] and increased [blank_start]shielding[blank_end] also means that an electron in a [blank_start]higher[blank_end] energy level is [blank_start]gained[blank_end] [blank_start]less[blank_end] easily, as there is less attraction from the [blank_start]nucleus[blank_end]. Thus, Group [blank_start]7[blank_end] metals are [blank_start]less[blank_end] reactive as you go down the group.

Properties of the [blank_start]Alkali Metals[blank_end] (Group 1): - They get [blank_start]more reactive[blank_end] as you go down the group. - Their melting and boiling points [blank_start]decrease[blank_end] as you go down the group. - They have a [blank_start]low density[blank_end]. - They have one [blank_start]outer electron[blank_end]. - They form [blank_start]ionic[blank_end] compounds with [blank_start]non-metals[blank_end]. - They react with [blank_start]water[blank_end] very vigorously to produce [blank_start]hydrogen gas.[blank_end].

Properties of the [blank_start]Halogens[blank_end] (Group 7): - They get [blank_start]less reactive[blank_end] as you go down the group. - Their melting and boiling points [blank_start]increase[blank_end] as you go down the group. - They all exist as [blank_start]diatomic molecules[blank_end]. - They form [blank_start]ionic[blank_end] bonds with [blank_start]metals[blank_end]. - They can [blank_start]displace[blank_end] less reactive halogens from an [blank_start]aqueous solution[blank_end] of that halogen's [blank_start]salt[blank_end].

Complete the table showing the properties of different halogens.

Properties of the Transition Metals (Middle of the Table): - They conduct [blank_start]heat and electricity[blank_end]. - They are very [blank_start]dense[blank_end], [blank_start]strong[blank_end] and [blank_start]shiny[blank_end]. - They are [blank_start]less reactive[blank_end] than Group1 metals. - They are much [blank_start]denser[blank_end], [blank_start]stronger[blank_end] and [blank_start]harder[blank_end] than the Group 1 metals. - They have [blank_start]much higher[blank_end] melting and boiling points than the Group 1 metals. - They often have more than one [blank_start]ion[blank_end]. - Their compounds are often [blank_start]colourful[blank_end]. - They all make good [blank_start]catalysts[blank_end].

What is the charge on a halide when it forms an ionic compound?