Study sheet: The Basics of Atomic Chemistry

📋 Course Outline

1. Atomic Structure and Subatomic Particles
2. Atomic Number and Mass Number
3. Isotopes and Relative Atomic Mass
4. Elements, Compounds and Molecules
5. Mixtures and Their Types
6. Separation Techniques

📖 1. Atomic Structure and Subatomic Particles

🔑 Key Concepts & Definitions

• Atom : the smallest part of an element that still has the properties of that element

📝 Essential Points

• A proton is located in :

  • the nucleus

  • has relative charge +1

  • has relative mass 1

• A neutron is located in :

  • the nucleus

  • has neutral relative charge

  • has relative mass 1

• An electron is located in :

  • an energy level

  • has relative charge −1

  • has relative mass 1/1,840

📌 An atom is neutral because it contains equal numbers of positively charged protons and negatively charged electrons.

💡 Memory Hook

The nucleus holds massive protons and neutrons, whereas the energy levels hold tiny electrons.

📖 2. Atomic Number and Mass Number

🔑 Key Concepts & Definitions

• Atomic number : the number of protons in the nucleus of an atom of that element
• Mass number : the number of protons and neutrons in the nucleus of an atom of that element

★ Must-know

• The number of neutrons equals $\text{mass number} - \text{atomic number}$.

Further detail

• For a neutral atom, the number of electrons equals the atomic number because it equals the number of protons.

• A magnesium-24 atom has 12 protons, 12 electrons, and 12 neutrons.

💡 Memory Hook

ID = atomic number: the proton count identifies the element.

📖 3. Isotopes and Relative Atomic Mass

🔑 Key Concepts & Definitions

• Isotopes : atoms of the same element with the same atomic number but different mass numbers because they contain different numbers of neutrons
• Relative atomic mass : the average mass of the isotopes of an element, taking natural abundances into account, relative to 1/12 of the mass of a carbon-12 atom

📝 Essential Points

• Carbon-12, carbon-13, and carbon-14 are isotopes containing 6 protons and respectively 6, 7, and 8 neutrons.

• Carbon has a relative atomic mass of 12.011 because its isotopes occur in unequal natural abundances: 98.89% carbon-12, 1.11% carbon-13, and 0.0000000001% carbon-14.

💡 Memory Hook

Isotopes share protons but differ in neutrons and mass number.

📖 4. Elements, Compounds and Molecules

🔑 Key Concepts & Definitions

• Mixture : made up of substances, including elements and compounds, mingled together but not chemically combined

📝 Essential Points

• In a mixture, each substance retains its chemical identity, and the mixture can have variable composition and melting and boiling points.

📖 5. Mixtures and Their Types

★ Must-know

📌 A homogeneous mixture is uniform throughout, whereas a heterogeneous mixture is not uniform throughout.

Further detail

• Air is an example of a homogeneous mixture, whereas orange juice with pulp is an example of a heterogeneous mixture.

💡 Memory Hook

Homogeneous mixtures are uniform throughout, whereas heterogeneous mixtures are not.

📖 6. Separation Techniques

🔑 Key Concepts & Definitions

• Filtration : a separating technique that separates insoluble solids from liquids
• Evaporation : a separating technique that separates a soluble solid and a liquid by evaporating the liquid and leaving the solid behind
• Distillation : a separating technique that separates mixture components based on their boiling points

★ Must-know

📌 Gravity filtration uses gravity to pull liquid through filter paper, whereas vacuum filtration uses suction from a Büchner flask and is faster and more efficient.

• During distillation, the more volatile component evaporates first, its vapour passes through a condenser, cools and condenses, and the resulting liquid is collected as the distillate.

Further detail

• In filtration, the insoluble solid retained by the filter paper is the residue, and the liquid that passes through is the filtrate.

• A mixture of ethanol and water can be separated by heating it above ethanol’s approximately 78°C boiling point but below water’s 100°C boiling point.

💡 Memory Hook

Filter, evaporate, or distil according to whether the component is insoluble, dissolved, or separated by boiling point.

📊 Synthesis Tables

Subatomic Particles

Particle	Location	Relative charge	Relative mass
Proton	Nucleus	+1	1
Neutron	Nucleus	Neutral	1
Electron	Energy levels	−1	1/1,840

Separation Techniques

Technique	Separated components	Basis
Filtration	Insoluble solid and liquid	Retention by filter paper
Evaporation	Soluble solid and liquid	Evaporation of the liquid
Distillation	Components with different boiling points	Vaporisation and condensation