Chapter 2 Flashcards
Atoms, ions and compounds
Define relative isotopic mass
The average mass of an atom of an isotope of an element relative to 1/12th of the mass of a Carbon 12 atom.
Define 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 ( related to percentage abundance and mass of each isotope )
What are mass spectrometers and how do they work ?
Ionisation : gaseous sample of atoms injected and stream of electrons fired to hit ions and create ions with + charge ( electron is lost )
Acceleration : entire sample enters then electromagnet used to accelerate ions to have same kinetic energy, pushing them through
Drift region : ion detector only recognises ions. Ek= 0/5 x m x (v) squared. Velocity is inversely proportional to mass of ion. Sample is separated due to different masses. Heavier ion = large mass = lower velocity = travel slower = slower to reach detector
Define isotope
Atoms of the same element that have the same number of protons and electrons but a different number of neutrons.
What is the atomic number of an element ?
Number of protons / electrons in the nucleus
What is the mass number of an element ?
The sum of protons and neutrons in the nucleus
What is the role of a mass spectroscoper ?
It determines the % abundance of the isotopes in an element.
What compound is produced when it is a metal + non metal ?
Ionic
What compound is produced when it is a non metal + non metal ?
Covalent
Charge on Ammonium ion (NH4)
1+
Charge on Hydroxide ion (OH)
1-
Charge on nitrate ion (N03)
1-
Charge on nitrite ion (NO2)
1-
Charge on cyanide ion (CN)
1-
Charge on Hydrogencarbonate ion (HCO3)
1-
Charge on Hydrogen sulfate ion (HSO4)
1-
Charge on Manganate(VII) ion (MnO4)
1-
Charge on Carbonate ion (CO3)
2-
Charge on Sulfate ion (SO4)
2-
Charge on Sulfite ion (SO3)
2-
Charge on Sulphide ion ( S )
2-
Charge on Dichromate ion (Cr2O7)
2-
Charge on Thiosulfate ion (S2O3)
2-
Charge on Phosphate ion ( PO4)
3-
Charge on Hydride ion (H)
1-
Charge on Zinc ion (Zn)
2+
Charge on Silver ion (Ag)
1+
Charge on Nitride ion ( N )
3-
Charge on Phosphide ion ( P )
3-
3 steps to write out formulae of ionic compounds
Work out the formula and charges of the separate ions.
Work out how many of each ion is needed to get overall charge of zero.
Put bracket around any polyatomic ion present more than once in the formula.
Formula of covalent compounds for single, two, three and four atoms
Mono, di, tri, tetra
Most elements are shown as their chemical symbol in equations. What is the exception ?
Elements that exist as small molecules.
Diatomic molecules = H, N, O, F, Cl, Br, I ( exist as 2 )
Phosphorus = P4
Sulfur = S8 but written as S in equations
What elements exist in the (g) state ?
H2, N2, O2, F2, Cl2 and noble gases
What elements exist in the (l) state ?
Br2 and Hg ( Mercury )
What elements exist in the (s) state ?
Everything apart from :
H2, N2, O2, F2, Cl2 and noble gases
Br2 and Hg ( Mercury )
State symbol for ionic compounds
Solids ( if water present most will dissolve aqueous ( but not all ) )
State symbol for covalent compounds
Water = liquid
Ammonia = gas
Carbon dioxide = Gas
How to write a chemical equation
Balance symbol equation.
Write correct formulae of chemicals present.
Include state symbols if asked to.
Ensure there is same type and number of atoms on both sides of equation so that final equation is balanced.
