Atomic structure and mixtures Flashcards
What is a compound?
A substance in which the atoms of two or more particles have chemically joined together
What is a molecule?
More than one non metal atom chemically joined together
Why do elements in the same group have similar properties?
Because they have the same number of electrons in their highest energy level
What is an isotope?
Atoms of the same element that have the same number of protons but a different number of neutrons
Why are the chemical properties of isotopes the same?
Because they have the same number of electrons
What is relative atomic mass?
An average mass taking into account the different masses of isotopes that make up the element and how abundant each isotope is
How do you calculate relative atomic mass?
(isotope abundance x isotope mass number) ÷ (sum of abundances of all the isotopes)
How did John Dalton describe the atom?
Solid spheres
How did JJ Thompson describe the atom?
A ball of positive charge with electrons studded into it - the plum pudding model
How did Ernest Rutherford describe the atom?
The atom is largely empty space and has a nucleus where most of the mass is concentrated, surrounded by electrons in a ‘cloud’ - the nuclear model
What was the alpha particle scattering experiment and what did it prove?
The experiment involved firing atoms at a sheet of gold foil and most of them either passed through the foil or were deflected from their path. This proved that the atom must be largely empty space and have a nucleus where most of the mass is concentrated
How did Niels Bohr describe the atom and why?
Scientists realised that electrons in a ‘cloud’ surrounding the nucleus would be attracted to it and cause the atom to collapse. Bohr suggested that the electrons surround the nucleus in shells and orbit the nucleus at a fixed distance
Who discovered the neutron?
James Chadwick
How did John Newlands arrange the periodic table?
- Put the elements in order of atomic weight
- Didn’t allow for undiscovered elements
- Mixed up metals and non metals
How did Dimitri Mendeleev arrange the periodic table?
- Arranged the elements in order of their atomic weight
- Left gaps for unknown elements and predicted their properties
- In some places he changed the order based on atomic weight
