Chemistry Topic 1 - Atomic Structure

Atom radius

0.1 nanometers / 1 x 10^-10 meters

Nucleus radius

Less than 1/10000 of the radius of an atom / 1 x 10^-14 meters

Atom

Smallest part of an element that can exist

Element

A substance made of only one type of atom

Compound

Two or more elements chemically combined in fixed proportions

Chemical formula of a compound

Shows the ratio of atoms of each element present

Mixture

Two or more elements or compounds not chemically combined together

Chemical bonds in a mixture

There are no chemical bonds between the separate substances

Filtration

Separates an insoluble solid from a liquid

Crystallisation

Separates a soluble solid from a liquid by heating to leave crystals

Simple Distillation

Separates a liquid from a solution based on boiling points

Fractional Distillation

Separates a mixture of liquids with different boiling points using a fractionating column

Chromatography

Separates substances based on their different solubilities in a moving solvent

Plum pudding model

Atom is a ball of positive charge with negative electrons embedded in it

Alpha particle scattering experiment

Fired alpha particles at thin gold foil; some deflected; proving a dense positive nucleus

Nuclear model

Mass is concentrated at a charged nucleus with electrons orbiting around it

Niels Bohr

Suggested electrons orbit the nucleus at specific distances in energy levels (shells)

James Chadwick

Discovered neutrons in the nucleus approximately 20 years after the nuclear model

Proton charge

+1

Neutron charge

0

Electron charge

-1

Proton relative mass

1

Neutron relative mass

1

Electron relative mass

Negligible / 1/2000

Overall charge of an atom

Zero / Neutral because proton number equals electron number

Atomic number

The number of protons in an atom

Mass number

The sum of the protons and neutrons in an atom

Isotope

Atoms of the same element with the same protons but different numbers of neutrons

Relative atomic mass calculation

(mass of isotope 1 x % abundance) + (mass of isotope 2 x % abundance) / 100

Maximum electrons in 1st shell

2 electrons

Maximum electrons in 2nd shell

8 electrons

Maximum electrons in 3rd shell

8 electrons

Periodic table arrangement

Arranged in order of increasing atomic number

Periodic table groups

Vertical columns where elements have the same number of outer shell electrons

Periodic table periods

Horizontal rows representing the number of electron shells an atom has

Early periodic tables

Arranged strictly by atomic weight which placed some elements in incorrect groups

John Newlands

Arranged elements by atomic weight and noticed a pattern of octaves but did not leave gaps

Dmitri Mendeleev

Arranged elements by atomic weight but left gaps for undiscovered elements

Isotope discovery impact

Proved Mendeleev was right to not strictly follow atomic weights due to different weights

Metals

Elements that react to form positive ions / found on the left and bottom of the table

Non-metals

Elements that do not form positive ions / found on the right and top of the table

Group 0 name

Noble Gases

Group 0 properties

Unreactive non-metals that are monatomic gases

Noble gases

They have a stable full outer shell of electrons (8 electrons except Helium which has 2)

Group 0 boiling point trend

Boiling points increase down the group due to an increase in intermolecular forces

Group 1 name

Alkali Metals

Group 1 physical properties

Soft metals with low densities that can be cut with a knife

Group 1 outer shell electrons

1 electron

Group 1 reaction with water

Produces a metal hydroxide (alkaline solution) and hydrogen gas

Group 1 reaction with chlorine

Produces a white metal chloride salt

Group 1 reaction with oxygen

Produces a metal oxide

Group 1 reactivity trend

Reactivity increases down the group

Group 1 reactivity explanation

Outer electron is further from the nucleus so there is less attraction and it is lost easier

Group 7 name

Halogens

Group 7 structure

Diatomic non-metals consisting of molecules containing two atoms (e.g. Cl2)

Group 7 outer shell electrons

7 electrons

Group 7 compounds with non-metals

Form covalent compounds

Group 7 compounds with metals

Form ionic salts with a -1 charge halide ion

Group 7 relative molecular mass trend

Increases down the group

Group 7 melting and boiling point trend

Increases down the group

Group 7 reactivity trend

Reactivity decreases down the group

Group 7 reactivity explanation

Outer shell is further from the nucleus so it is harder to attract and gain an electron

Group 7 displacement reaction

A more reactive halogen will displace a less reactive halogen from an aqueous salt solution

Transition metals location

The large central block of the periodic table between Group 2 and Group 3

Transition metals vs Group 1 strength

Transition metals are much harder

Transition metals vs Group 1 melting points

Transition metals have much higher melting points (except mercury)

Transition metals vs Group 1 reactivity

Group 1 alkali metals are extremely reactive, whereas transition metals are very unreactive and react incredibly slowly.

Transition metals unique property 1

Can form ions with different charges (e.g. Fe2+ and Fe3+)

Transition metals unique property 2

Form brightly colored chemical compounds

Transition metals unique property 3

Act as highly effective catalysts in industrial chemical reactions

Iron catalyst use

Used in the Haber Process to manufacture ammonia

Nickel catalyst use

Used in the manufacture of margarine

Syllabus examples of transition metals

Chromium, Manganese, Iron, Cobalt, Nickel, Copper

Copper (II) ions color

Blue in chemical compounds

Iron (II) ions color

Green in chemical compounds

Iron (III) ions color

Brown/Orange in chemical compounds