Chemistry - 1.6 - Periodic Table

• An element is a substance made up of only one type of atom that cannot be broken down into simpler substances by chemical means.
• Alkali metals have low density and low melting points and the first three are less dense than water.
• Alkali metals are soft, shiny when cut and tarnish rapidly.
• Alkali metals react with water to form hydrogen gas and metal hydroxide.
• When lithium reacts with water, there is no flame, it floats and the water remains colourless.
• When sodium reacts with water, there is no flame, it floats and the water remains colourless.
• When potassium reacts with water, it burns with a lilac flame, it floats, and bubbles of gas appear.
• Most group 1 compounds are white and dissolve in water to give colourless solutions.
• Fluorine is a pale yellow gas at room temperature.
• Chlorine is a pale green gas at room temperature and pressure.
• Bromine is a red brown liquid at room temperature.
• Iodine is a dark grey solid at RTP
• In group 7, the reactivity decreases going down the group.
• In group 7, toxicity decreases as you go down the group.
• When chlorine gas is present, damp universal indicator paper turns red then bleached white.
• The noble gases are colourless.
• The boiling points of the noble gases increase as you go down the group.
• The transition metals have higher melting and boiling point, higher densities and are less reactive than group 1 or 2 metals.
• Transition elements form ions with different charges and form coloured compounds.