SC17 Groups in the Periodic Table

• arranged in increasing atomic number • groups all have the same amount of electrons on the outermost shell • periods have the same amount of electron shells

Alkali metals

They form alkaline solutions when they react with water

• soft metals that can easily be cut with a knife • relatively low densities and low melting points • very reactive

group 1 metal + water –> metal hydroxide + hydrogen

They only have one electron in the outermost shells, which can be lost easily

Reactivity increases as we go down the group

The atoms themselves get bigger, so it is easier to lose an electron because there are weaker forces of attraction between the outermost electron and the nucleus

Fizzes steadily, slowly becomes smaller until it disappears

Melts to form a ball, fizzes rapidly, quickly becomes smaller until it disappears

Quickly melts to form a ball, burns violently with a lilac flame, disappears rapidly, often with a small explosion

Halogens

Pale yellow-green gas

red-brown liquid

Purple-black solid

• melting and boiling points increase as you go down the group • diatomic molecules • poor conductors of heat and electricity • toxic and corrosive

The intermolecular forces increase as you go down the group, because the atoms get larger, so much more energy is required to get over these forces

It turns damp blue litmus paper white

Decreases as you go down the group

Decreases as you go down the group because its outer shell is further away from the nucleus, which means the electron is harder to take on due to weak intermolecular forces

Metal halides

Hydrogen halides

Becomes less stable as you go down the group

When a more reactive halogen replaces a less reactive halogen