Flashcards in Atoms and Moles Deck (56)
What is the mass of an electron?
What is an isotope?
An atom with the same number of protons but different number of neutrons
What is the atomic number?
Number of protons
Why do some atoms of the same element have different mass numbers?
If they have different number of neutrons
What do ions have different numbers of?
Protons and Electrons
What is the relationship between protons and electrons in a negative ion?
There are more electrons than protons
What is the relationship between protons and electrons in a positive ion?
There are more protons than electrons
What 2 things affects the chemical properties of an element?
Number and arrangement of electrons
Why do isotopes not change the chemical properties of an element?
Isotopes have the same configuration of electrons so they've got the same chemical properties
What 2 physical properties are different with isotopes compared to elements?
Rates of diffusion
Who came up with one of the currently accepted models of the atom?
What did some ancient Greeks believe matter was made of?
They believed matter was made from invisible particles
What did John Dalton describe atoms as at the start of the 19th century?
Solid spheres (different types of sphere made up of the different elements)
What did JJ Thomson conclude after his experiments in 1897?
That atoms weren't solid and invisible
What did Thomson call the 'electrons'?
What was Thomson's model called?
Plum Pudding Model
What was the Plum Pudding model?
A positively charged sphere with negatively charged electrons embedded in it
What experiment did Rutherford conduct?
The gold foil experiment
What did Rutherford's gold foil experiment involve?
Firing alpha particles (+ve charge) at an extremely thin sheet of gold
What did Rutherford expect the result of his experiment to be (due to the Plum Pudding Model)?
That most of the alpha particles were to deflect slightly
What did Rutherford's gold foil experiment show?
That the plum pudding model was incorrect
What was the name of the model that Rutherford came up with?
What was the Nuclear Model?
An atom with a tiny, positively charged nucleus at the centre of it with a cloud of negative electrons
Where was most of the mass concentrated in the Nuclear Model?
At the centre, so most of the atom is empty space
What did Henry Moseley discover?
Charge of the nucleus increased from one element to another in units of one
After Moseley's discovery, what did Rutherford find when further investigating the nucleus?
That it called positively charged particles that he called protons
Who discovered the neutron?
What were the 4 principals of Bohr's model?
-Electrons only exist in fixed orbits (shells) and not anywhere in between
-Each shell has a fixed energy
-When an electron moves between shells EM radiation is emitted or absorbed
-Because the energy of the shells is fixed, the radiation will have a fixed frequency
What did the Bohr model explain about noble gases?
Why they were inert (chemically inactive)