atomic structure and the periodic table

Atoms

Smallest part of an element that can exist

Compound

2 or more elements chemically combined

Mixtures

Two or more element or compounds not chemically combined

Methods of separating misxturs

Filtration, fractional distillation, simple distillation, crystallisation, chromatography

Filtration separates?

Insoluble solid from a liquid

Crystallisation separates?

Insoluble solid from solvents

What is formed from salt during crystallisation

Crystals

Simple distillation

Separates liquids with different boiling points

Equipment needed for simple distillation (4)

Thermometer,

condenser,

apparatus ,

electric heater

How does simple distillation work

Turn heater on to degree of lowest boiling point then vapour rises through the condenser which cools down leaving liquid substance eg. Ethanol

Fractional distillation separates?

Many liquids at same time

Chromatography separates

Ink/ pigments from a mixture

Before the development of atoms what were they thought to be?

Tiny spheres that could not be divided

What was the first discovery about atoms

Electrons

After electons where discovered what model was made

Plum pudding model

Plum pudding model

Electrons embedded in a ball of positive charge

Alpha partical scattering experiment

Beams of alpha particles were fired at layer of thin gold foil and they passed through while some were deflected or reflected

What conclusions were made from the alpha particle experiment (3)

Most of the atom is empty space,

the atom has a positively charged centre

most of the charge and mass is concentrated in the centre

What model do we use today was developed after the alpha particles scattering experiment?

Nuclear model

Who adapted the nuclear model to suggest electrons orbit the nucleus at specific distances?

Neils bhor

What positively charged particle was discovered in the nucleus?

Proton

James Chadwick provided evidence of ??

Neurtons in the nucleus

Why are atoms always neutral?

Electrons and protons are same

Radius of atom

0.1nm (1×10^-10m)

Isotopes

Atoms of the same element with same number of protons but different number of electrons

Formula for calculating relative atomic mass with given abundance of isotopes

(% abundance x RAM) + (% abundance x RAM) / divided by 100

Before the discovery of sub atomic particles what were the elements in the periodic table arrange by?

Atomic weight

Why did Mendeleev leave gaps in the period table?

For undiscovered elements

Elements that form positive ions are

Metals

Elements that do not form positive ions are

Non metals

Properties of metals (5)

Hard, shiny,

high density,

good conductors of electricity and heat,

meallable,

high melting and boiling points

Properties of non metals (5)

Dull,

low density,

poor conductors or electricity and heat,

brittle,

low melting and boiling points

Which group is know as the noble gases?

Group 0

Group 0 atoms are unreacitve, why?

Full outer shell

As you go down group 0 the boiling point…

Increases

Why does the boiling point increase as you go down group 0

Force of attraction between atoms become larger therefore more energy is needed to overcome the forces

Which group is know as the alkali metals?

Group 1

When lithium, sodium and potassium react with water what do they all form

Metal hydroxide and hydrogen gas

What reaction happens when lithium reacts with water (3)

Bubbles/fizzes,

floats

moves around

What happens when sodium reacts with water (3)

vigorously fizzes/bubbles, floats and moves around , makes ball shape

What happens when potassium reacts with water (3)

Fizzes vigorously, ignites to produce lilac flame, floats and moves around

Why does reactivity increase as you go down group 1?

Electrons go further away from the positive nucleus meaning the electron gets more easily lost

Which group is known as the halogens?

Group 7

When group 7 elements react with non metals what happens

They share one pair of electrons

As you go down group 7 melting nd boiling points..

Increase

What happens when group 7 elements react with metals

They gain an electron

Why does the melting and boiling point increase as you go down group 7

Molecules get bigger so there are stronger forces of attraction between molecules so more energy is needed to separate them

Why does reactivity decrease as you go down group 7

Electron is further away from nucleus so there is less attraction for the metal meaning electrons are less easily gained

Explain displacement in group 7

A more reactive halogen can displace a less reaction halogen from an aqueous solution of its salt

Properties of group 1 metals

Low melting and boiling points, low density, soft, reactive, form white compounds, form ions with ONLY +1 charge, not used as catalyst

Properties of transition metals

High melting and boiling points, high density, hard , not very reactive, form coloured compounds, form ions with different charges and can be used as a catalyst