Chapter 1 Flashcards
How did John Dalton describe atoms
As solid spheres, he said that different spheres made up the different elements.
How did JJ Thompson describe atoms
He had a theory of the ‘plum pudding model’ He said that the atom was a ball of positive charge with electrons stuck in it.
How did Rutherford describe atoms and why
Using the gold foil experiment he fired positively charged alpha particles at an extremely thin sheet of gold. They expected the particles to pass straight through or be slightly deflected at most. However some were delflected more than expected this showed that the plum pudding model couldn’t be correct.
He came up with the idea that in an atom, there’s a tiny positively charged nucleus at the centre where most of its mass is concentrated and a cloud of negative electrons surrounding this nucleus.
What did Bohr say about the structure of an atom
The electrons where in shells that are in fixed distances from the nucleus
What are isotopes
Different forms of the same element, which have the same number of protons but different number of neutrons
What is the relative atomic mass of an element?
The average mass of one atom of the element compared to 1/12 of the mass of one atom of carbon-12
Boron has two isotopes, boron-10 and boron-11. Given that the relative abundances of these are 4 and 16. Work out the relative atomic mass of boron?
(10x4) +(11x16)= 216
216 / (16+4)= 10.8
How can you work out the electronic configuration of an element by looking at the periodic table
The period of the element is the number of shells it has.
The group of the element is the number of electrons it has on its outer shell
What is an ion
When atoms lose or gain electrons they become ions. Ions are charged particles
What is an ionic bond
strong electrostatic attraction between positive and negative ions
What structure does ionic compounds have
Giant ionic lattice
Properties of ionic compounds?
•high boiling and melting points due to strong bonds between the ions and a lot of energy needed to overcome these bonds.
•when they are solid the ions are held in place so the compounds can’t conduct electricity. When they melt the ions are free to move and they’ll carry an electric charge
What is covalent bonding
When a two or more nonmetals share a pair electrons resulting in energies overlapping
properties of diamond
each carbon molecule is bonded to 4 others
held together by strong covalent bonds which require a lot of energy to break so high melting point
this strong covalent bonds also make it a very strong material
It doesn’t conduct electricity as there are no free electrons
