science | at1 - the periodic table groups

what are periods in the periodic table

• the rows in the periodic table

• the atomic number increases by one as you go left to right

• every element grouped within the same period has the same amount of electron shells

what are groups in the periodic table

• the colums in the periodic table

• 18 groups throughout the whole periodic table

• group number indicates the amount of electrons in the valence shell of the element

  • the less amount of electrons in the valence shell, the more reactive it is

  • number of valence electrons determines the chemical and physical properties of elements (element properties in each group are similar)

  • exceptions are first 2 periods and the transition metals

alkali metals (group 1)

• most reactive metals

• form +1 ions

• too reactive to be found in their pure form

• react violently with water with explosion

• have typical metal properties

• are soft enough to cut with a knife

• display extreme chemical behaviour

• needed to be handled extremely carefully, they are stored in a bottle of kerosene to not come into contact with air or water

alkaline earth metals (group 2)

• high melting points

• form +2 ions

• act similar to group 1 but are slightly less reactive

• are slightly harder than alkali metals

• an alkaline solution can be formed when a metal oxide is dissolved in water

transition metals (groups 3 to 12)

• include the lanthanides and actinides

• generally, transition metals are lustrous, silvery, hard and good conductors of electricity and heat

• some are more malleable than others

• properties between individual elements may vary greatly

post transition metals

has some properties of post transition metals but are softer and conduct more poorly than them

metalloids

• form ions of +1

• located between the metals and non-metals in the periodic table

• sometimes behave as semiconductors rather than conductors

what are some of the properties of halogens? (group 17)

• subset of non-metals

• generally very chemically reactive

• present in the environment as compounds rather than pure elements

• form ions with a charge of -1

• are not found in nature in their pure form but are found in various salts

• get bigger and become less reactive as you move down a group

• all form molecules that are made up of 2 atoms