Key concepts Flashcards
How has the Dalton model developed over time (6)?
- Went through 4 scientists, Dalton, Thompson, Rutherford, Bohr
- Dalton thought that the atom was the smallest possible particle and couldn’t be divided
- JJ Thompson found out that the atom has electrons in it. He thought that the electrons were stuck inside the atom and called this the plum pudding model.
- Rutherford fired alpha particles at a gold leaf sheet. He expected most to go through. However, a few deflected more than normal, and some completely deflected, showing that there was a nucleus at the centre. He stated that there was a cloud of electrons in the atom
- Bohr refined the model and added energy levels.
State the electron’s mass
1/1836
How is relative atomic mass defined and how does it vary with isotopes?? (Ar)
- Average mass of one atom of the element compared to 1/12 of the mass of one atom of carbon-12
- If an element has more than one isotope, its Ar is the average of the mass numbers and abundancy of the isotope.
How do you find the RAM with isotopic abundancies?
multiply each relative isotopic mass by its isotopic abundance and add up the results. Divide by sum of the abundance.
How does Mendeleev’s periodic table arranged?
by atomic mass. Left out gaps where he thought there was undiscovered elements
How was Mendeleev able to predict the existence of certain elements which had not been discovered?
Mendeleev found out that elements in the same group have similar properties, so he was able to find gaps.
What do the endings -ide and -ate mean
ending -ide means that the compound contains two ions
ending -ate means that the compound contains three or more ions, one of which is oxygen
Explain the structure of an ionic compound
- Giant ionic lattice
- strong electrostatic forces of attraction in all directions
Properties of ionic compounds?
(melting point, solubility, ability to conduct electricity)
- Lots of energy to break strong bonds between ions, therefore high melting and boiling point
- Can conduct electricity while aqueous because the ions can move, while not as solids because the ions are fixed.
- Usually soluble in water
Properties of simple molecular compounds?
(melting point, solubility, ability to conduct electricity)
- Low melting point because intermolecular bonds are weak and require little force to overcome.
- The larger the molecule, the stronger the intermolecular forces.
- The molecules have no charge, so can’t conduct electricity
- Some are soluble, some aren’t
Properties of giant covalent structures?
(melting point, solubility, ability to conduct electricity)
- Very high melting point due to strong covalent bonds which must be overcome to melt and boil the substance
- Not soluble
- No charged particles, so don’t conduct electricity (apart from graphene and graphite)
Properties of metallic structures?
(melting point, solubility, ability to conduct electricity)
- High melting and boiling point because of large forces of attraction between the sea of electrons and the positive metal ions
- insoluble in water
- Conducts electricity due to sea of electrons
What are the uses of graphite?
- Electrodes, conducts electricity due to one delocalised electron
- Weak intermolecular forces between layers and no covalent bonds, making the layers slide over eachother
What are the uses of diamond?
- Cutting tools due to its rigid structure and strong covalent bonds.
What are simple polymers?
Large molecules containing chains of carbon atoms
