Topic1 Key Concepts In Cehmsitry Flashcards
What are the relative mass and relative charge of:
Proton
Neutron
Electron
Proton:
Relative mass:1
Relative charge:+1
Electron:
Relative mass:
Relative charge:-1
Neutron:
Relative mass:1
Relative charge:+1
Where are protons and electrons and neutrons located?
Protons:nucleus
Neutrons:nucleus
Electrons:around nucleus in shells
What are atoms neutral?
Because they have equal number of protons and electrons and so charges cancel out making the charges 0
What is the atomic number and mass number?
How calculate the neutrons?
Atomic number:protons
Mass number:protons+neutrons
Neutrons:mass number-atomic number
What are isotopes?
Different forms of the same element
Same number of protons and different number of electrons
How do you work out relative atomic mass of an element?
Multiply each relative isotopic mass by its isotopic abundance
Add them up
Divide by sum of abundance
Give two differences and 1similaritiy in Mendeleev periodic table to the one today?
Differences:
Gaps in Mendeleev compared to today
Mendeleev sorted elements in order of atomic mass
Today’s one sorted elements in order of atomic number
Similarities:both periodic table was laid out in similar properties
What is the maximum amount of electrons filled in the 1st,2nd and 3rd shell?
1st-2 electrons
2nd-8 electrons
3rd-8 electrons
What are ions?
What is an anion?
What is cation?
Ion-single atoms or groups of atoms
Anion-when atoms gain electrons
Cation-when atom loses electrons
What do group 1 and 2 elements do to form positive ions?
What do group 6 and 7 elements do to form negative ions?
Lose electrons
Gain electrons
What is the overall charge of an ionic compound?
Why?
0
Because all negative charges must balance all the positive charges
What is ionic bonding?
The transfer of electrons that is held by ionic bonds that are electrostatic forces
What are the properties of ionic compounds?
High melting and boiling point:due to strong attractions between the ions
Don’t conduct electricity in a solid:due to ions in fixed place and can not move.
Conduct electricity when melted:ions free to move and so carry current
Conduct electricity when dissolved in water:ions are separate and free to move in solution so carry current.
What is a covalent bond?
A strong bond that forms when pair of electrons is shared between two atoms
What are properties of simple molecular compounds?
Atoms within the molecules are held by strong covalent bonds
Don’t conduct electricity:don’t contain any free ions
Low boiling and melting point:weak intermolecular forces break down easily
What are properties of giant covalent structures?
All atoms are bonded by strong bonds
Very high melting and boiling points:lot of energy needed to break the bonds
Are not soluble in water
Explain the properties of diamond?
Made up of a network of carbon atoms that each form 4 covalent bonds
High boiling and melting point:Strong covalent bonds
Rigid lattice structure:makes diamond hard and so used for cutting tools
Does not conduct electricity:has no free electrons or ions
Explain the properties of graphite?
Each carbon atom forms 3 covalent bonds creating sheet of carbon atoms arranged in hexagons
Aren’t any covalent bonds between the layers:held together weakly so free to move and slip of each other.Used as a lubricant
High melting point:covalent bonds in layers need loads f energy to break
Conducts electricity:Only 3 out of carbons 4 outer electrons used in bonds, so 1 electron is free and delocalised to carry current
Explain the properties of graphene?
It’s a sheet of carbon atoms joined together in hexagons
2D compound:One atom thick
Explain properties of buck minster fullerene:
Fullerenes are carbon shaped like hollow balls.
Made up of carbon atoms arranged in hexagons
Huge surface area:used as catalyst in industry
What are properties of metals?
High boiling and melting points:strong electrostatic forces
Shiny solids
Conduct electricity and heat:as delocalized electrons carry electrical current and heat energy through materials
Dense:ions in metallic structure packed together
Malleable-can be rolled or hammered into flat sheets
What are the properties of non metals?
Low boiling point
Dull and brittle
Low density
How to work out empirical formula?
- Work out how many moles of each elements you have
2. Work out smallest whole ratio by simplifying
How do you calculate moles?
Mass/Mr
How can you use an experiment to find the empirical formula?
- get crucible and heat
- leave crucible to cool and weigh it with its lid
- add clean magnesium ribbon to crucible.Reweigh crucible magnesium ribbon and lid
- heat crucible containing magnesium put lid on crucible stop oxygen escaping but leave a gap to allow oxygen to enter
- heat crucible strongly for 10mins unit magnesium ribbon turns white
- allow crucible to cool and redesign crucible with lid and content.
- minus the mass of crucible and lid from mass of magnesium oxide
What is a limiting reagent?
The reactant that is used up on a reaction
Why is the product formed directly proportional to the amount of limiting reactant used?
Because if you add more of the limiting reactant there will be more reactant particles which means more product particles are made.
How do you calculate amount of product from limiting reagent?
- write out balance equation
- work out Mr of reactant and product you are interested in
- find number of moles of substance you know mass off
- use balanced equation to work out how many moles there will be of other substance
- use the number of moles to find mass
