Groups Of The Periodic Table Flashcards
What is another name for group one metals ?
Alkali metals
Give the properties and features of the elements in group one
- Very reactive.
- All are soft easily cut metals , exposing a shiny surface.
- The shiny surface rapidly tarnishes in air.
- All have low density.
- All have relatively low melting points for metals.
- All are stored under oil to prevent reaction with oxygen and moisture in the air.
- All react vigorously with water and burn in air.
- All the atoms have one electron in their outer shell.
- All form simple ions with a charge of +.
- all have a valency of one
- all conduct electricity
What are the trends going down group one.
- The reactivity increases.
- The melting point decreases.
Why do all group one elements have similar properties
Because they have one electron on their outer shell
When group one atoms react what happens
They lose they’re one outer shell electron to form an ion. The ion has a full outer shell of electrons and is stable. The one has a single positive charge.
What alkali metals float on water and how do they do this ?
Sodium potassium and lithium float on the surface of water becuase they are less dense than water
Do alkali metals have a low or high density
Low
What are the observations when lithium reacts with water
Lithium floats on the surface
Moves about on the surface
Fizzes/gas is given off
Eventually disappears
Heat is released
Colourless solution is formed
What are the observations when sodium reacts with water ?
It floats on the surface
Forms a silvery ball/melts
Moves about the surface
Fizzes/gas given off
Eventually disappears
Heat is released
Colourless solution forms
What are the observations for the reaction of potassium with water
Floats on surface
Moves about surface
Burns with a lilac flame
Fizzes/gas is given off
Eventually disappears
Small explosion / crackle
Heat is released
Colourless solution is formed
What is the general equation for group one metals reacting with water
Metal + water —> Metal hydroxide + hydrogen
Why are rubidium and caesium not generally used in laboratories
They are highly reactive and they’re reactions in water are explosive
What is the half equation for sodium
+ -
Na —> Na + e
Describe group one compounds
They are almost all white solids and room temperature and pressure and they dissolve in water to form colourless solutions.
What is another name for group seven elements
The halogens
What are the properties and features of the group seven elements
- reactive non-metals.
- all coloured.
- all exist as diatomic molecules
- all react with group one elements to form solid , white ionic compounds.
- all group seven elements have seven electrons in their outer shell.
- all form simple halide ions with a charge of - , for e.g. Cl-
- all have a valency of one
- they do not conduct electricity
- all the halogens are toxic
What are the trends going down group seven ?
- colour intensity of the elements darkens and melting point increases.
- the melting point increases down the group and this explains why there is a clear trend from gas to liquid to solid.
What are the physical properties of flourine
- Yellow gas at room temp.
- F molecules - molecular covalent.
2 - melting point is -220 degree’s
What are the physical properties of chlorine ?
- Green gas at room temp
- Cl Molecules - molecular covalent
2 - Melting point = 101 degrees
What are the physical properties of bromine
- Red brown liquid at room temperature
- Br Molecules - molecular covalent
2 - Melting point = 7 degrees
What happens when you heat iodine
They grey black solid changes to a purple vapour on heating and the purple vapour changes back to grey black crystals on cooling. This is known as sublimation.
Explain the trend in reactivity in grouo seven elements
- when a group seven element reacts it gains one outer shell electron which completes its outer shell.
- the elements become less reactive as you go down the group because the atom gains the electron less readily
- ## the reason for this is the distance of the outer shell from the attractive power of the the positive nucleus. If the electron is gained into a shell close to the nucleus then it is gained very readily
What are the observations when chlorine displaces bromide ions from solution
The yellow-green gas dissolved in the solution and the solution changes from colourless to orange
What are the observations when chlorine displaces iodide ions from solution
The yellow-green gas dissolves in the solution and the solution changes from colourless to brown
