Moles and Atoms Flashcards
Avogadros number
6.02 x 10^23
How many protons, neutrons and electrons does hydrogen have?
P - 1
E - 1
N - 0
The relative molecular mass of Hydrogen is? Why?
- Because it has one proton and no neutrons
Mass of an electron relative to a proton
~ 2000x less
What is a standard solution?
A solution that has a known concentration of all parts
What makes an idea primary standard?
- be pure
- be stable (not oxide in the air or absorb oxygen)
- not absorb moisture from the air
- have a relatively large molecular mass
Examples of primary standards:
Potassium hydrogen phthalate (KHP) (standardises aqueous alkalis) sodium carbonate (standardizes aqueous acids)
What is a volumetric flask?
Glassware that is accurately calibrated to calculate volume
1ml is ? cm^3?
1 cm^3
Atomic number is:
Number of protons in the nucleus (Z)
Atomic mass number is…
Number of protons and electrons of an element. (A)
Isotopes have the same…
- Number of protons
- Number of electrons
- Atomic Number
- Chemical properties
Isotopes have different…
- Number of neutrons
- mass number
- physical properties
What is an isotope
Atoms of the same element (same number of protons/atomic number) with a different number of neutrons (different mass number)
Relative isotopic mass
The mass of one atom of an isotope relative to 1/12th of the mass of carbon-12.
Because they are relative values, they don’t have numbers
Relative atomic mass
The mass of one atom of an element relative to 1/12th of carbon-12
Define Ionisation Energy
The energy required to remove one electron from each atom of one mole of gaseous atoms to form one mole of gaseous +1 ions. Normally given in kj/mol.
Ionisation energy of lithium…
519kj/mol
If the ionization energy is positive the reaction is endothermic or exothermic?
Endothermic
An endothermic reaction is one which…
has a positive ionization energy. i.e. the energy is provided
What four factors effect ionization energy?
- Charge on the nucleus
- Atomic radius
- Electron shielding
- Electron configuration
Equation for the gradient of the line
y = mx + c
How to work out y in the equ^n y = mx + c
The value of Y when x = o
How to work out the gradient of the line
Choose two separate points on the line, note down their coordinates. Draw a triangle from both points using the slop of the line as the hypotenuse. Work out the change along the x-axis and the change along the y-axis, then do ∆y/∆x.
Energy levels
Atomic energy levels are the energies of electrons
in atoms. Quantum theory tells us that each
electron has a definite energy. When atoms gain or
lose energy the electrons may jump from one
energy level to another.
Group (periodic table)
A group is a vertical column of elements in the
periodic table. Elements in the same group have
similar properties because they have the same
outer electron configuration.
Mass to charge
ratio
The mass to charge ratio, m/z, is the ratio of the
relative mass, m, of an ion to its charge, z.
Spectrometers usually operate so that z is normally
1.
Period (periodic table)
A period is a horizontal row of elements in the
periodic table.
Relative formula mass
The relative formula mass of a compound is the
sum of the relative atomic masses of all the atoms
in its formula.
Define Shielding
This is the effect of the inner electrons which
reduces the pull of the nucleus on the electrons in
the outer shell of an atom. Because of the shielding
the electrons in the outer shell are attracted by an
‘effective nuclear charge’ which is less than the full
charge on the nucleus.
Extrapolation
Extrapolation of a graph extends the line beyond
the experimental range of values.
Independent variable
The one condition that is changed in the experiment
Ordinary form
This is a number written with no powers of ten
included.
Proportion
Proportion is the ratio of a part compared to the
whole amount.
Standard form
This writes a number in two parts multiplied
together. The first part is a number greater than 1
and less than 10, the second part is the number 10
raised to a power which is a whole number.
Theoretical yield
A theoretical yield is the mass of product obtained
if the reaction goes according to the equation.
Variable
A variable in an experiment is an item, factor or
condition that can be controlled, changed or
measured.
Weighted mean
A weighted mean is an arithmetic mean of a set of
numbers in which some of the numbers carry more
significance than others.
Shell n = 1 holds how many electrons?
2
Shell n = 2 holds how many electrons?
8
Shell n = 3 holds how many electrons?
18
Shell n = 4 holds how many electrons?
32
Names of sub-shells
s, p, d, f
Sub-shells are divided into
Atomic orbitals
Atomic orbitals are defined by…
- Energy leve;
- Shape
- Direction in space
What shape is formed by the s orbital?
Sphere/circle
What shape is formed by the p orbitals?
Figure of 8
