Chemical Periodicity Flashcards
Explain the term mass number
The number of protons and neutrons in the nucleus of an atom.
Explain the term isotope
Atoms of the same element that have different numbers of neutrons. (same number of protons)
In the modern version of the periodic table the elements are arranged in increasing order of…
atomic number
Explain what is meant by a group, and what do its members have in common
A column down the periodic table; same number of electrons in the outer shell
Explain what is meant by a period and what its members have in common.
Row across the table; same number of electron shells
Describe the trend in chemical reactivity down the group one elements and explain the reason for it.
On descending the group the outer shell electron becomes further from the pull of the protons in the nucleus. Therefore become progressively eassier to remove the metal’s outer electron and turn te atom into a positive ion, so the metals become more reactive.
Although the number of protons inthe nucleus increaed, this is compensated for by the ‘sheilding’ efect of the increased number of inner electrons shells.
Describe what you would see when chlorine gas is bubbled through aqueous potassium bromide.
The solution would turn orange due to the formation of aqueous bromine.
Describe what you would see if magnesium chloride is mixed with silver nitrate solution.
A white precipitate
What is the family name of the group 1 elements
The alkali metals
When a group 1 metal is reacted with water, a solution is formed. What would the pH of the resulting solution be
14
Describe the test for hydrogen.
Squeaky pop test. A lit splint is put into a test tube of hydrogen and a squeaky pop would be heard.
The elements become more reactive as we go down the group 1. Give one piece of evidence to justify this statement.
Group 1 metals react by losing one electron. There would be more effervescence down the group and the flame produced by Hydrogen..
Explain why the valency of group one metals is always 1.
There is one electron in the outer shell of each element so the valency is 1
Predict two physical properties of astatine
A dark solid, not a good conductor. Solid at room temperature.
What is the test for chlorine.
Chlorine gas turns damp blue litmus paper red then bleaches it white.
Test for chloride in NaCl.
Sodium chloride is dissolved in water then add silver nitrate solution and nitric acid. If there is a white precipitate then chlorine is present.
Test for Sodium in NaCl.
Sodium when heated with a Bunsen burner, turns the flame orange.
What is the gas produced on heating sodium nitrate and what is the test for it.
Oxygen, relights a glowing splint.
What is the gas produced on heating sodium hydrogencarbonate and what is the test for it.
Carbon dioxide which turns limewater cloudy.
What is the gas produced on adding lithium to water.
Hydrogen which makes a squeaky pop when a lit splint is put in it.
How do you construct an ionic equation
Write out the full chemical equation including state symbols. Rewrite the equation splitting uo all those things that are both aqueous and ionic (acids are split up into H+ ions and a negatively charge ion). Cancel out spectator ions.
What are group 1 elements at room temperature
White crystalline solids.
What is the trend in reactivity down the halogen group and explain why it happens.
F is the most reactive halogen because it has the strongest electrostatic attraction for an incoming electron. This is because the outer shell of F (which is where the electron is going) is closer to the nucleus than the outer shells of the other halogens.
What is the use of Chlorine
Disinfectant in swimming pools, chemical weaponry (antique)
Use of Fluorine
It is added to drinking water and tooth paste. It is good for teeth apparently.
Use of Iodine
Iodine has similar effects to chlorine but to a milder extent and so is often used as an antiseptic that is safe for humans.
Group 0- The noble gases are all colourless. How do their density and boiling point change down the group?
Density increases and boiling point increases.
Trends in the halogens going down the group.
Become less reactive, become darker, increase in melting/boiling point.
Colour of aqueous bromine.
Orange
Colour of aqueous iodine.
Brown.
Test that iodine is present.
Add hexane and shake which forms a purple layer on the aqueous solution.
Colour of silver chloride.
White
Colour of silver bromide.
Cream
Colour of silver iodide.
Yellow
Trends upon descending group one?
- Becoems more reactive
- Become softer
- Increase in density
What is the use of helium?
- Filling party ballons and airships - helium is less dense than air
What is the use of neon?
- Filling gas discharge tubes - to make neon advertising signs
What is the use of Argon?
- Provide an inert atmosphere, e.g. lightbulbs to prevent oxidation of the filament, in welding to prevent the metal from burning, in packaging to prevent spoiling of food
What is the use of krypton?
- In lasers
Use of xenon?
- In flash lamps for cameras
What are the properties of fluorine?
- Pale yellow gas
- Very toxic
- Extremely reative
What are the properties of chlorine?
- Pale green gas
- Dense
- Toxic
What are the properties of bromine?
- Dense
- Dark red liquid
- Gives of red-brown vapour
- Toxic
- Corrosive
What are the properties of Iodine?
- Dark grey solid
- Sublimes to give a purple vapour
- Forms a brown solution in water
- Forms purple solution in hexane
What happens when halgens are heated with alkali metals?
- Brun vigorously to form white crytalline halide salts.
- These are ionic compounds - elctrons are transferred form metal to the non etal atoms, forming negatively charged halide ions.
How can you test the halide ions in sodium chlrodie, sodium bromdie and sodium iodide?
- Place a small smaple of solution in test tuve
- Add few drops of nitric acid
- Then add a few drops of silver nitrate solution
What happens when hydrogen halides are dissolved in water?
- The molecules spilt up, giving H+ ion and therefore an acidic solution.
