the periodic table Flashcards
Periodic table
Elements are arranged on the Periodic table in order of increasing atomic number, where each element has one proton more than the element preceding it.
The table is arranged in vertical columns called Groups numbered 1 – 8 and in rows called Periods.
Period: these are the horizontal rows that show the number of shells of electrons an atom has.
E.g: elements in Period 2 have two electron shells, elements in Period 3 have three electron shells.
Group: these are the vertical columns that show how many outer electrons each atom has.
E.g: Group 4 elements have atoms with 4 electrons in the outermost shell, Group 6 elements have atoms with 6 electrons in the outermost shell.
Predicting properties using the Periodic table
Because there are patterns in the way the elements are arranged on the Periodic table, there are also patterns and trends in the chemical behaviour of the elements.
There are trends in properties down Groups and across a Period.
All of the Group I elements, for example, react very quickly with water.
In this way the Periodic table can be used to predict how a particular element will behave.
The metallic character of the elements
The metallic character of the elements decreases as you move across a Period on the Periodic table, from left to right, and it increases as you move down a Group.
This trend occurs due to atoms more readily accepting electrons to fill their valence
shells rather than losing them to have the below, already full, electron shell as their outer shell.
Metals occur on the left-hand side of the Periodic table and nonmetals on the right-hand side.
Between the metals and the nonmetals lie the elements which display some properties of both.
These elements are referred to as metalloids or semi-metals.
Properties of metals and nonmetals
Electronic configuration and the Periodic table
The electronic configuration is the arrangement of electrons into shells for an atom (e.g electronic configuration of carbon is 2, 4).
There is a link between the electronic configuration of the elements and their position on the Periodic table.
The number of notations in the electronic configuration will show the number of shells of electrons the atom has, showing the Period.
The last notation shows the number of outer electrons the atom has, showing the Group number.
Example: Electronic configuration of Chlorine:
Chemical properties of elements in the same group
Elements in the same Group in the Periodic table have similar chemical properties.
When atoms collide and react, it is the outermost electrons that interact.
The similarity in their chemical properties stems from having the same number of electrons in their outer shell.
For example, both lithium and sodium are in Group 1 and can react with elements in Group 7 to form an ionic compound (charges of Group 1 ions are +1, charges of Group 7 ions are -1).
The Group I metals
The Group I metals are also called the alkali metals as they form alkaline solutions with high pH values when reacted with water.
Group 1 metals are lithium, sodium, potassium, rubidium, caesium and francium.
They all contain just one electron in their outer shell.
Physical properties of the Group I metals
The Group I metals:
Are soft and easy to cut, getting softer and more dense as you move down the Group (sodium and potassium do not follow the trend in density).
Have shiny silvery surfaces when freshly cut.
Conduct heat and electricity.
They all have low melting points and low densities and the melting point decreases as you move down the Group.
Chemical properties of the Group I metals
They react readily with oxygen and water vapour in air so they are usually kept under oil to stop them from reacting.
Group 1 metals will react similarly with water, reacting vigorously to produce an alkaline metal hydroxide solution and hydrogen gas.
Reactions of the Group I metals and water
Explaining the trend in reactivity in Group I
The reactivity of the Group 1 metals increases as you go down the group.
Each outer shell contains only one electron so when they react, they lose the outer electron which empties the outermost shell.
The next shell down automatically becomes the outermost shell and is already full, hence the atom obtains an electronic configuration which has a full outer shell of electrons.
As you go down Group 1, the number of shells of electrons increases by 1 (Period number increases down the Periodic table).
This means that the outer electron is further away from the nucleus so there are weaker electrostatic forces of attraction.
This requires less energy to overcome the electrostatic forces of attraction between the negatively charged electron and the positively charged nucleus.
This allows the electron to be lost easily, making it more reactive as you go down the Group.
Properties of other Alkali Metals (Rubidium, Caesium and Francium):
As the reactivity of alkali metals increases down the Group, rubidium, caesium and francium will react more vigorously with air and water.
Lithium will be the least reactive at the top and francium will be the most reactive at the bottom.
Francium is rare and radioactive so is difficult to confirm predictions.
Predicted Reaction with Water
The halogens
These are the Group 7 non-metals that are poisonous and include fluorine, chlorine, bromine, iodine and astatine.
Halogens are diatomic, meaning they form molecules of two atoms.
All halogens have seven electrons in their outer shell.
They form halide ions by gaining one more electron to complete their outer shells.
Colours and States at Room Temperature
Trends in Physical Properties of the halogens
Melting Point
The density and melting and boiling points of the halogens increase as you go down the Group.
State at Room Temperature
At room temperature (20 °C), the physical state of the halogens changes as you go down the Group.
Chlorine is a gas, bromine is a liquid and iodine is a solid.
Colour
The halogens become darker as you go down the group.
Chlorine is pale green, bromine is red-brown and iodine is black.
Aqueous Solution Colour of Halogens
