Deck 1 Flashcards
What are the main features of an atoms structure?
- Protons+Neutrons make up the nucleus.
- Nucleus is tiny compared with the total volume of an atom.
- Nucleus is extremely dense and makes up almost all of the atoms mas.
- Most of an atom consists of empty space between the tiny nucleus and and the electron shells.
What are the main features of an atoms structure?
- Protons+Neutrons make up the nucleus.
- Nucleus is tiny compared with the total volume of an atom.
- Nucleus is extremely dense and makes up almost all of the atoms mas.
- Most of an atom consists of empty space between the tiny nucleus and and the electron shells.
What are the main features of an atoms structure?
- Protons+Neutrons make up the nucleus.
- Nucleus is tiny compared with the total volume of an atom.
- Nucleus is extremely dense and makes up almost all of the atoms mas.
- Most of an atom consists of empty space between the tiny nucleus and and the electron shells.
What is the relative mass and charge of a proton?
Relative mass = 1
Relative charge = -1
What is the relative mass and charge of a neutron?
Relative mass= 1
Relative charge = 0
What is the relative mass and charge of an electron?
Relative mass = 1/2000
Relative charge = - 1
Isotopes of the same element have?
- Different masses
- The same number of protons and electrons
- different numbers of neutrons in the nucleus.
What two numbers describe an element?
The atomic number(proton number)- the number of protons in the nucleus.
-The mass number(nucleon number) - the number of particles(protons and neutrons) in the nucleus.
How can you work out the number of neutrons an isotope has?
Subtract the mass number by the proton number.
For an isotope, relative isotopic mass=
atomic mass
When measuring atoms masses by comparing them to carbon-12, what assumptions have been made?
- We have neglected the tiny contribution that electrons make to the mass of an atom.
- We have taken the masses of both a proton and a neutron as 1.0u.
What does the weighted mean mass mean?
Most elements contain a mixture of isotopes, each in a different amount and with a different mass. We use the term “weighted mean mass” to account for the contribution made by each isotope to the overall mass of an element.
What does the contribution made by an isotope to the overall mass depend on?
- the percentage abundance of the isotope
- the relative mass of the isotope
A sample of bromine contains 53% of bromine-79 and 47% of bromine-81. Determine the relative atomic mass of bromine.
79.94 ( Go to page 9 for an example )
What is the relative mass and charge of a proton?
Relative mass = 1
Relative charge = -1
What is the relative mass and charge of a neutron?
Relative mass= 1
Relative charge = 0
What is the relative mass and charge of an electron?
Relative mass = 1/2000
Relative charge = - 1
Isotopes of the same element have?
- Different masses
- The same number of protons and electrons
- different numbers of neutrons in the nucleus.
What two numbers describe an element?
The atomic number(proton number)- the number of protons in the nucleus.
-The mass number(nucleon number) - the number of particles(protons and neutrons) in the nucleus.
How can you work out the number of neutrons an isotope has?
Subtract the mass number by the proton number.
For an isotope, relative isotopic mass=
atomic mass
When measuring atoms masses by comparing them to carbon-12, what assumptions have been made?
- We have neglected the tiny contribution that electrons make to the mass of an atom.
- We have taken the masses of both a proton and a neutron as 1.0u.
What does the weighted mean mass mean?
Most elements contain a mixture of isotopes, each in a different amount and with a different mass. We use the term “weighted mean mass” to account for the contribution made by each isotope to the overall mass of an element.
What does the contribution made by an isotope to the overall mass depend on?
- the percentage abundance of the isotope
- the relative mass of the isotope
A sample of bromine contains 53% of bromine-79 and 47% of bromine-81. Determine the relative atomic mass of bromine.
79.94 ( Go to page 9 for an example )
What is the relative mass and charge of a proton?
Relative mass = 1
Relative charge = -1
What is the relative mass and charge of a neutron?
Relative mass= 1
Relative charge = 0
What is the relative mass and charge of an electron?
Relative mass = 1/2000
Relative charge = - 1
Isotopes of the same element have?
- Different masses
- The same number of protons and electrons
- different numbers of neutrons in the nucleus.
What two numbers describe an element?
The atomic number(proton number)- the number of protons in the nucleus.
-The mass number(nucleon number) - the number of particles(protons and neutrons) in the nucleus.
How can you work out the number of neutrons an isotope has?
Subtract the mass number by the proton number.
For an isotope, relative isotopic mass=
atomic mass
When measuring atoms masses by comparing them to carbon-12, what assumptions have been made?
- We have neglected the tiny contribution that electrons make to the mass of an atom.
- We have taken the masses of both a proton and a neutron as 1.0u.
What does the weighted mean mass mean?
Most elements contain a mixture of isotopes, each in a different amount and with a different mass. We use the term “weighted mean mass” to account for the contribution made by each isotope to the overall mass of an element.
What does the contribution made by an isotope to the overall mass depend on?
- the percentage abundance of the isotope
- the relative mass of the isotope
A sample of bromine contains 53% of bromine-79 and 47% of bromine-81. Determine the relative atomic mass of bromine.
79.94 ( Go to page 9 for an example )
What is the equation relating amount if substance n, mass m and molar mass M?
n=m/M
n=amount of substance
m=mass, in g
M= molar mass, in g mol^-1
Empirical formula
The empirical formula is the simplest whole-number ratio of atoms of each element present in a compound.
Analysis showed that 0.6075 g of magnesium combines with 3.995 g of bromine to form a compound.
Empirical formula MgBr2
Analysis of a compound showed the following percentage composition by mass:
Na: 74.10% , O:25.81%
Find the ratio of atoms.
Na2O
What is the molecular formula used for?
It is used fro compounds that exist as simple molecules.
What does a molecular formula tell you?
A molecular formula tells you the number of each type of atom that make up a molecule.
A compound has an empirical formula of CH2 and a relative molecular formula mass, Mr, of 56.0. What is its molecular formula?
C4H8
What is the equation relating the amount of has molecules,n, in mol , the gas volume, V, in dm^3.
n=V/24dm^3
( this is because all substances take up the same amount of volume as gases providing they have the same number of moles )
What is the volume, in cm^3, of 2.130 x 10^-3 mol of a gas at RPT?
51.12cm^3
What does a concentration of a solution tell you?
The concentration of a solution tells you how much solute is dissolved in the solvent.
What does a solution of 2 mol dm^-3 tell you?
There are 2 moles of solute dissolved in every 1dm^3 of solution.
What equation relates the amount of substance, concentration of solute and volume of solution?
n = c x V Where: - n= amount of substance, in mol. - c= concentration of solute, in mol dm^-3 - V= volume of solution, in dm^3
What is the amount, in mol, of NaOH dissolved in 25.0cm^3 of an aqueous solution of concentration 0.0125mol dm^-3?
3.125 x 10^-4 mol