2 -Compounds, Formulae And Equations Flashcards
What is an atom?
The smallest particles of an element yhat have the chemical properties of that element
E.g. Ne
What is a molecule?
Molecules form when 2 or more atoms form chemical bonds with each other. (Can be different or the same)
H
²
What is an ion
A charged atom
Na (+)
Cl (-)
What is an element?
An element contains only one type of atom
E.g. He
What is a mixture?
2 or more substances not chemically bonded together
What is a compound
2 or more subtances chemically bonded together in fixed proportions
- Relative atomic mass, Mr definition
The ratio of average mass of one atom of an element to one twelfth of the mass of an atom of carbon 12
Relative molecular mass, Mr definition
Is the weighed mean mass of a molecule, compared with one 12th of the mass of of carbon 12
Relative formula mass mr definition
compares the mass of a formula unit with the mass of an atom of Carbon-12
Trick: is an acid a molecule or ion?
ACIDS ARE ALWAYS IONS
1 Pico meter =
1pm = 1 x 10 to the power of -12 m
What is the relative mass unit?
u
The relative charge of a proton is?
+1
The relative charge of a neutron is?
0
The relative charge of an electron is?
-1
The relative mass of a proton is?
1
The relative mass of a neutron is?
1
THE RELATIVE MASS OF AN ELECTRON IS?
1/1836
NOT 1/2000 -> Not specific enough
Relative atomic mass definition?
Ar
Weighted mean mass of an atom of an element compared with 1/12 of the mass of an atom of carbon 12
Relative isotopic mass definition?
Is the mass of an atom of an isotope compared with 1/12th of the mass of an atom of Carbon 12. NO AVERAGES
Orbital definition?
A region around the nucleus which can hold up to 2 electrons with opposite spins
What is the definition of a shell?
A shell is made up of a number of atomic orbitals that that all have the same PRINCIPAL QUANTUM NUMBER (shell number)
What is a sub shell?
A group of orbitals within a shell that have the same shape and energy e.g 3p
Working out the Ar
Ar = total (% x mass number)
- % ÷ 100 to get the decimal
How to calculate the total number of electrons?
2n²
n= shell number
How are spins paired?
1 clockwise, 1 anticlockwise
Key: what order do the orbitals fill up in?
4S fills BEFORE 3d
Special elements for configuration?
Cromium and Copper
Cr key configuration
4s has 1 electron As 3d fills entirely
Cu key configuration
3d fills entirely to get full 3rd shell
4s¹
Why are Cu and Cr exceptions?
4s and 3d subshells are very close in energy. Moving the electrons from 4s to the empty 3d orbital reduces repulsion between electrons
How to write a short notation for electronic configuration?
[Proceeding noble gas] then the rest of it
Number of moles equation?
Moles = Mass/ Mr
What actually is 1 mole?
One mole is the amount of substance that contains 6.02 ×10 ²³ particles
What is a molecule?
How many of the whole thing/ unit
Number of atoms equations?
Moles × Avagadro’s number
How many ions in total?
WORK OUT SEPARATELY AND ADD TOGETHER
How many significant figures?
The significant figures in the question or 3 if in doubt
Significant figures rule
The 0 at the end of a number are Significant IF they come at the end of a decimal point
Important rule for significant figures in calculations?
- ROUND YOUR FINAL ANSWER TO A CALCULATION TO THE SAME NUMBER OF SIGNIFICANT FIGURES AS THE DATA VALUE WITH THE FEWEST SIGNIFICANT FIGURES USED IN THE CALCULATION
What unit do we always work in for mass?
ALWAYS ROUND TO GRAMS
Empirical formula definition?
Simplest whole number ratio of atoms of an element in a compound
What do we need to calculate molecular formula?
We need the know empiricial formula and the Mr
Steps of how to calculate molecular formula?
-work out me of empirical formula
- divide Mr of compound/ Mr of empiricial formula
- take this value and multiple the empirical formula by this.
( 4 × CH. ) = C. H
² ⁴ ⁸
empirical formula always is….
Atoms
If percentage is given instead of mass…
Assume that the compound weighs 100g and take the percentage for the mass
Salts made by neutralisation have to be…
Ionic
Anhydrous salt definition?
The water of crystalisation has been removed
Hydrated salt definition?
Is a salt that has water of crystallization as part of its structure
CuSO • 5 H O
⁴ ²
Calculations using hydrated salts REMEMBER?
To minus the water from the salt mass
1 mole of gas has the same value because?
The volumes of particles is small in comparison to the spaces between particles so 1 mole of any gas has the same value
1dm³=
1000cm ³
Volume triangle
N = volumes (cm³) / 24000
… (dm³)/ 24
basic principle of a mass spectometer?
- a sample is placed in the mass spec
- the sample is then vapourised and ionised to form = ions
- the ions are accelerated. heavier ions mover slower and are more diff to deflect than lighter ions, so the ions of each isotope are seperated
- the ions are detected on a mass spectrum as a mass to charge ratio m/z. each ion reaching the detector adds to the signal, so greater abundabce = larger signal
mass to charge ration m/z =
relative mass of ion/ relative charge on ion
for an ion with one + charge?
this ratio is equivalent to the relative isotopic mass
determination of relative isotopic mass?
the mass spec can also record the accurate m/z ratio for each isotiope so that accurate values of relative isotopic mass can be measured
the ionic charge of a transition metal is shown how?
with a Roman numeral in the name of the ion
what is a binary compound?
contains 2 elements ONLY
how to name a binary compound?
- use the name of the first element but change the ending of the 2nd to elements name to -ide
- for ionic, the metal ion always comes first
what is a polyatomic ion?
- an ion that contains more than 1 element bonded together (phosphate, hydroxide, carbonate)
what is a formula unit?
- the formula worked out in from the ionic charges is used in equations
always add?
state symbols
what is an ion?
a molecule with a net charge
when are molecular ions formed?
when groups of 2 or more atoms are covalently bonded lose/gain electrons
during a chemical reaction, no atoms are
created/ destroyed, they are rearraneged
spectator ions appear in both
reactants and products
in ionic equations, the spectator ions can be removed to produce the?
net ionic equation
which chemical reaction can be used to differentiate between isotopes?
none bc as isotopes are chemically identical (same no of electrons)
atomic mass units
unified atomic mass unit (u)
a mass spectrum can be used to?
- identify an unknown compund
- provide structural info abt the molecule
- determine the relative abundance of each isotope of an element
acronym for mass spec
Vaporisation Ionisation Acceleration Deflection Detection
Molecular formula def?
The actual number of atoms of each type of element in a molecule
Ionic equations?
Can write for any reaction involving ions that happens in solution
• any reacting particles (and the products they form) re included
• cross out any ions that appear both side of the equation
