Year 10 Chemistry Unit 1

Patterns in groups

• no. valence electrons

• no. shells increasing by 1 each time

Patterns in periods

• no. shells

• electrons increase by 1

• protons increase by 1

• valence electrons increase by 1

What elements do periodic table patterns count for

All elements except transition metals

Group 1 pattern

• 1 valence electron

• alkali metals

Group 2 Pattern

• 2 valence electrons

• alkali earth metals

Group 13 pattern

• 3 valence electrons

Group 15 pattern

• 5 valence electrons

Group 16 patterns

• 6 valence electrons

Group 17 pattern

• 7 valence electrons

• Halogens

Group 18

• Full outer shell

• noble gases

Proton mass

1

Neutron mass

1

Electron mass

almost 0

Proton charge

+1

neutron charge

0

electron charge

-1

Electron Configuration

2,8,8,2

Periods

Horizontal rows

Groups

Vertical columns

Electron Arrangement

Shows the number of electrons in each shell

Isotopes

• Atoms with the same number of protons but a different number of neutrons

• Atoms of the same element with different mass numbers

relative Atomic mass / average atomic mass

average of the atomic masses of all the different isotopes in a sample

Relative atomic mass formula

(%1xAM2)/100 + (%2xAM2)/100 + …

Ion

Atom of an element that has gained or lost electrons (no longer neutral) - has a positive or negative charge

Positive Ion

• Cation

• Atom has more protons than electrons

• Atom loses an electron

• Positive net charge

Negative Ion

• Anion

• Atom Gains an electron

• More electrons than protons

• Negative net charge

Valence electrons

Electrons in the outermost shell of an atom

Elements forming anions and cations

Metals form cations, non-metals form anions

Chemical Reaction

A process in which one or more substances are converted to one or more different substances

Open System

Has external interactions, molecules and energy can both move in and out

Closed System

Molecules cannot move in and out but heat can still be transferred

Isolated System

No transfer of molecules or energy

Law of Conservation of Mass

Mass is neither created nor destroyed, mass is conserved from reactants to products

Law of Conservation of mass formula

Mass(reactants)=Mass(products)

Symbol Equations

must be balanced to give the correct ration of reactants and products

Absolute Uncertainty

+- smallest increment/2

Avogadro’s number

6.022×10²3 atoms

Molar Mass

equal to the atomic mass of each substance

Moles formula

Moles(n)=mass(g)/molecular mass (gmol^-1)

Molarity

number of moles of solute per litre of solution

Molarity formula

C(mol/L)=N(mole)/V(L)