Topic 1 - Atomic Structure & the Periodic Table

Atoms

The smallest part of an element that still has its chemical properties.;

Nucleus

The centre of the atom containing protons and neutrons.;

Protons

Positive charge particles with mass 1 found in the nucleus.;

Neutrons

Neutral particles with mass 1 found in the nucleus.;

Electrons

Negative particles with almost no mass that orbit the nucleus.;

Atomic Number

Number of protons in an atom.;

Mass Number

Total number of protons and neutrons in an atom.;

Elements

Substances made of only one type of atom.;

Isotopes

Atoms of the same element with same protons but different neutrons.;

Relative Atomic Mass (Ar)

Weighted average mass of an element’s isotopes compared to carbon-12.;

RAM Formula

(isotope mass × abundance) ÷ total abundance.;

Compounds

Two or more elements chemically combined in fixed proportions.;

Molecules

Two or more atoms covalently bonded together.;

Mixtures

Two or more substances not chemically bonded and easily separated.;

Chemical Formulas

Tell you what atoms and how many are in a compound.;

Balancing Equations

Balancing atoms on each side using big numbers only not changing small numbers in formulas.;

States of matter 4

(s) solid (l) liquid (g) gas (aq) dissolved in water.;

Filtration

Separates an insoluble solid from a liquid using filter paper.;

Crystallisation

Obtains crystals by evaporating solvent to leave solid behind.;

Distillation

Separates liquid from solution by evaporation and condensation.;

Fractional Distillation

Separates a mixture of liquids with different boiling points.;

History of the Atom

Models developed from Dalton to Thomson to Rutherford to Bohr to Chadwick.;

Dalton Model

Atoms were solid spheres with no internal structure.;

Thomson Model

Discovered electrons and proposed plum pudding model.;

Rutherford Model

Nuclear model in which a tiny positive nucleus is surrounded by electrons.;

Bohr Model

Electrons orbit in fixed shells with specific energy levels.;

Chadwick

Discovered neutrons in the nucleus.;

Electronic Structure

Electrons arranged in shells 2 in first 8 in second and third.;

Electron Configuration Example

Sodium is 2 8 1 showing one outer electron causes high reactivity.;

Development of the Periodic Table

Mendeleev arranged elements by atomic mass leaving gaps for undiscovered elements.;

Modern Periodic Table

Arranged by atomic number not mass.;

Groups

Vertical columns showing number of electrons in outer shell.;

Periods

Horizontal rows showing number of electron shells.;

Metals

Elements that form positive ions good conductors malleable and ductile.;

Non-metals

Poor conductors gain electrons to form negative ions.;

Group 1 Properties

Soft reactive metals reactivity increases down the group.;

Group 1 Reactions

React with water to form metal hydroxide and hydrogen.;

Why Group 1 Reactivity Increases

Outer electron is further from nucleus so easier to lose.;

Group 7 Properties

Halogens reactive non-metals reactivity decreases down the group.;

Group 7 Displacement

A more reactive halogen displaces a less reactive halogen from solution.;

Group 0 Properties

Unreactive gases with full outer shells.;

Group 0 Trends

Boiling point increases down the group due to stronger intermolecular forces.;