Module 2 Chapter 2

Module 2 Chapter 2

2.1 Atomic Structure and isotopes

Sub-atomic particles

2.2 Relative Mass

2.3 Formulae

Relative masses used to compare as real masses are too small

Ions

2.3 Balanced Equations

Protons

Neutrons

Electrons

Charge- +1

Charge- 0

Charge- -1

Mass- 1

Mass- 1/1836

Most of mass in nucleus- where protons and neutrons found

Overall mass of atom= 0

Electrically neutral

Atomic number

p+=e-

Hold nucleus together

Isotopes

Mass number

Number of protons in an atom

Identifies the element

Every atom of the same element has same number of protons

Periodic table in order of atomic number

Atoms of same element with different number of neutrons but same number of protons and electrons

Chemical reactions involve outer electrons- isotopes react in same way

Have slightly different physical properties

Number of protons and neutrons in an atom

Ions

Charged atom

Anions

Negative ions

Cations

Positive ions

Lose electrons

Gained electrons

Carbon-12

All atomic masses compared to it

Mass exactly known- -1.99x10-26 kg

Mass of one atom- 12u (atomic mass units)

Relative atomic mass

Weighted mean mass of an atom relative to 1/12th of the mass of an atom of Carbon-12

Relative Isotopic Mass

Mass of an atom of an isotope relative to 1/12th of the mass of one atom of Carbon-12

Takes into account

% abundance of each isotope

Relative isotopic mass of each isotope

Mass spectroscope

Identifies the relative isotopic mass and relative abundance of each element

How it works

1)Sample placed in it

2) Sample vaporised and ionised- +ve ions

3) Ions accelerated- heavier ions slower- longer to reach detector

4) Ions detected and appear on mass spectrum

x-axis= m/z and y-axis=% abundance

RAM Calculation- (M1x%)+(M2x%)/100

Metals lose electrons to form cations

Non-metals gain electrons to form anions

Metal Ions

Copper (II)- Cu2+

Copper (I)- Cu+

Iron (II)- Fe2+

Iron (III)- Fe3+

Silver- Ag+

Zinc- Zn2+

Polyatomic ions

Nitrate- NO3-

Sulphate- SO42-

Ammonium- NH4+

Hydroxide- OH-

Carbonate- CO32-

Ion Endings

Ends in ide- only that element

Ends in ate- something else as well as the element usually oxygen

Covalent

Ionic

1) work out formula and charges of separate ions

2) Work our number of each ion to make it electrically neutral

3) Put brackets around polyatomic ions present more than once

Can deduce most by looking at their name

Reactants on left

Mono- single atom

di- two

tri- three

tetra- four

Products on right

State symbols

(S)- Solid

(l)- Liquid

(g)- Gas

(aq)- Aqueous solution

Atoms cannot be created or destroyed

Key Tips

Put balancing numbers in front of formulae

Don't change any formulae

Add state symbols

You can use fractions

Combustion equation

Only one mole of the compound is combusted so fractions may be needed to balance it