2.1.1 atomic structure and isotopes Flashcards
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Definition of Atomic number
The number of protons in an elements nucleus.
Definition of Atomic mass
The number of protons and neutrons added to together.
Definition of relative isotopic mass
The mass of an isotope relative to 1/12th of the mass of an atom of carbon-12.
Definition of relative atomic mass
The weighted mean mass of an atom of an element relative to 1/12th of the mass of an atom of carbon-12.
Definition of an isotope
An isotope is an atom of the same element with the same number of protons but a different number of neutrons and therefore different masses.
What are the relative charges and masses of the 3 types of sub-atomic particle?
Proton 1+ relative charge, relative mass of 1
Neutron 0 relative charge, relative mass of 1
Electron 1- relative charge, relative mass of 1/1836
Why do isotopes have the same chemical properties, but different physical properties?
The mass of an isotope determines its physical properties and the electrons determine the chemical properties. As an isotope has the same number of electrons it will have the same chemical properties no matter how many neutrons it has.
What is an ion?
An ion is a charged atom.
What are the two different types of ion?
Cation- positively charged, has fewer electrons than protons.
Anion- negatively charged, has more electrons than protons.
How are ions shown?
Ions are shown with their charge, to show that they are ions.
What is the unit for relative isotopic mass?
Relative isotopic mass has no units because it is a ratio of 2 masses.
How do you determine the relative atomic mass?
Mass spectrometers are used to find out the percentage abundance of each isotope and the relative isotopic mass of each isotope. From this you can use an equation to work out the relative atomic mass.
How do you work out the relative atomic mass?
Step 1: Use the percentage abundance and multiply by the mass-to-charge ratio of each isotope. E.g. For Chlorine 35 and 37 are the mass-to-charge ratios.
Step 2: add these two numbers together.
Step 3: divide the number from the previous calculation by 100, so that it is no longer a percentage.
Name the diatomic molecules.
H2, N2, O2, F2, Cl2, Br2 and I2.
What are the state symbols and why are they used?
(g) gas
(l) liquid
(s) solid
(aq) aqueous/ dissolved in water
They are used to indicate physical change in chemical reactions.
What is meant by the term empirical formula?
The empirical formula is the simplest whole number ratio of atoms of each element in a compound.
Why is an empirical formula important?
An empirical formula is important for substances that do not exist as small molecules. These can be metals or non-metals such as silicon, carbon and ionic compounds like NaCl.
What is the equation that links moles, mass and molar mass?
n=m÷M
n= amount of substance moles
m= mass
M= molar mass
Volume measurements.
1cm3= 1ml 1dm3= 1000cm3=1000ml=1l
How do you convert between moles and solution volumes?
n=c x V
n= amount of substance, moles
c= concentration, moldm3-
V= volume dm3
When using cm3 as volume the equation changes to
n= c x (V ÷ 1000)
How do you work out standard solution?
for example, how much of x is required to prepare y cm3 of a z moldm3 standard solution?
Step 1: work out the moles required by using
n= c x (V ÷ 1000).
Step 2: work out the molar mass e.g molar mass of H2O is 18.0
Step 3: rearrange the formula n=m ÷ M to calculate the mass of x required
What is an ionic bond?
The electrostatic attraction between ions.
How do you find the number of particles in a substance?
N= n x Na
N= number of particles n= amount of substance (mol) Na= Avogadro's constant
How do you find the amount of substance in mol?
n= N ÷ Na
n= amount of substance N= number of particles Na= Avogadro's constant
