C1 - Atoms

What do chemical reactions cause?

Atoms to change what they’re bonded to

Element

A substance containing only one type of atom

Compound

A substance containing two or more different types of chemically bonded

Conservation of mass

Atoms can be neither created nor destroyed

Mixture

Contains different substances not chemically bonded

Filtration

Removes large insoluble particles from a liquid

Evaporation

Leaves behind crystals of a dissolved substance (solute) if heated gently (crystallisation)

Distillation

Involves condensing the evaporated solvent and collecting it

Fractional Distillation

Can seperate liquids due to their different boiling points

Chromatography

Causes substances to rise up paper due to capillary action, lighter particles move further up

Solid → Gas

Sublimation

What is needed to overcome the electrostatic between particles, to melt / evaporate?

Heat

Physical Change

No new substance is made

Aqueous

In solution

1st atomic model

John Dalton

Solid spheres

2nd atomic model

JJ Thompson

Plum pudding model

Posistive sphere with electrons dotted randomly

3rd atomic model

Ernest Rutherford

Nucleus is small and positively charged

Most alpha particles went directly through a gold leaf, very few deflected back

4th atomic model

Niels Bohr

Electrons exist in shells

5th atomic model

James Chadwick

Discovered the neutron

A?

+1

B?

0

C?

-1

D?

1

E?

1

F?

0 (very small)

Isotope

Same element, same number of neutrons, different number of neutrons

Mass number

The number of protons and neutrons in a nucleus

Atomic number

(or relative atomic mass) is the number of protons in a nucleus. An atom must also have this number of electrons in order to be neutral, if not is is an ion

Why are some numbers on the periodic table not integers?

They are an average mass of all isotopes

Calculation for relative atomic mass

total mass of atoms / total number of atoms

How were elements initially ordered in the periodic table?

By atomic weight

What was Dmitri Mendeleev order his periodic table?

Reversed and swapped some elements and kept gaps for elements that had not yet been discovered

Group

Number of atoms in outer shell

What do metals always do to gain a full outer shell?

Donate electrons to form positive ions

What do non-metals always do to gain a full outer shell?

Accept electrons to gain a full outer shell, either become negative ions or share electrons

What are Group 1 know as?

The alkali metals

What happens when a group one metal reacts with water?

Produce an alkali

What do Group 1 metals do to gain a full outer shell?

Lose their outer electron, so their ions are always 1+

What happens to reactivity as you go down group one and why?

Gets more reactive because the outer electron is further away from thenucleus so is donated more readily

What are Group 7 elements known as?

Halogens

What do Group 7 elements do to gain a full outer shell?

Gain 1 electron to form 1- ions

What happens to the reactivity of group 7 elements as you go down the group?

Get less reactive

What happens to the boiling point of group 7 elements as you go down the group?

Increases

What is special about the noble gases?

They are unreactive as they already have a full outer shell

What is special about transition metals?

They can donate different numbers of electrons