Periodic Table

today’s periodic table

1869

Properties of transition metals

Hard, dense, unreactive to water, strong, can be used as a catalyst, high boiling points.

Group

Column, elements with similar properties and the same number of electrons in the outer shell. (eg group 7 elements have 7 electrons in their outer shell.)

Period

Row, same number of shells.

Newlands model

Arranged in atomic mass. He did not leave space for new elements in his table, therefore some elements were not similar. Proposed law of octaves, every 8 elements were similar but only worked until calcium.

Mendeleevs table

Arranged in atomic number, spaces were left for undiscovered elements and predicted the properties of these

particle allowed elements to be arranged in atomic number

Protons

Describe group 1 elements.

Increase reactivity further down the table, white in colour, reactive with water (alkali metal + water = metal hydroxide + hydrogen) , soft, low density

Describe group 7 elements.

Halogens, diatomic molecules (come in 2) , only group where elements exist in all states, boiling point e down the group (large molecules hard to seperate), reactivity decreases - shielding and distance, forms salt when reacts with group 1 metals.