Atoms and Moles Flashcards
What is the mass of an electron?
1/1840
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?
Different densities
Rates of diffusion
Who came up with one of the currently accepted models of the atom?
Bohr
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’?
Corpuscles
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?
Nuclear Model
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?
James Chadwick
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)
How did the Bohr Model explain why the noble gases are inert?
He said that atoms can only hold a fixed number of electrons in a shell, and that an element’s reactivity is due to it’s electrons. So, when a shell is full of electrons, it’s stable and doesn’t react
What is the relative atomic mass?
The weighted mean mass of an atom of an element compared to 1/12th of the mass of a an atom of carbon-12
Why are some relative atomic masses not a whole number in the periodic table?
Because it is an average mass of all the isotopes
What is the relative isotopic mass?
The weighted mean mass of an atom of an isotope compared to 1/12th the mass of an atom of carbon-12
What are mass spectrometers?
Devices which are used to find out what samples are made up of by measuring the masses of their components
What is the relative molecular mass?
The average mass of a molecule compared to the mass of an atom of carbon-12
How do you find the Mr?
Add up the relative atomic mass values of all the atoms in the molecule
What is the relative formula mass?
The average mass of a formula unit compared to 1/12th the mass of an atom of carbon-12
How do you find the relative formula mass?
Add up the relative atomic masses of all the ions in the formula unit
What is a mole?
The unit for an amount of a substance
How many particles are there in 1 mole?
6.02x10^23
What is the equation linking number of moles, mass and molar mass?
Moles=Mass/Molar Mass
What is molar mass?
The mass of one mole of something
What similarities are there between the molar mass and the relative formula mass?
They have the same numerical value, just for molar mass you put ‘g mol^-1’ (grams per mole)
What equation links number of moles, number of particles you have and number of particles in a mole?
Moles=Number of particles you have/Number of particles in a mole
What equation links number of moles, volume (dm^3)?
Number of moles = Volume (dm^3)/24
What equation links number of moles, volume (cm^3)?
Number of moles = Volume (cm^3)/24000
What is the ideal gas equation?
pV=nRT where p=pressure, V=volume (m^3), n=number of moles, T=temperature (K) and R=the gas constant (J K^-1mol^-1)
What is the gas constant value?
8.314 J K^-1mol^-1
What does the SI unit pf the gas constant mean?
Units of energy per temperature increment per mole
What does 2kPa equal?
2000 Pa
How do you convert from oC to K temperature?
You add 273
What is the concentration of a solution?
How many moles (or grams) of something are dissolved per 1 dm^3 of solution
Describe what a dilute solution is
A solution that has fewer moles per dm^3 than another
Describe what a concentrated solution is
A solution that has more moles per dm^3 than another
What equation links number of moles and concentration and volume (in cm^3)?
Number of moles=(Concentration x Volume)/1000
What equation links number of moles and concentration and volume (in dm^3)?
Number of moles=Concentration x Volume
