Atomic Structure and Subatomic Particles

This section introduces the fundamental concepts of atomic structure, including the definition of atoms, elements, compounds, and mixtures. It also covers the historical development of atomic theory and the properties of subatomic particles.

Definition: An atom is the smallest part of an element that can exist, with a neutral overall charge.

The history of atomic theory is presented chronologically, highlighting key contributors:

1. Democritus: Proposed the idea of indivisible particles separated by empty space.
2. John Dalton: Introduced the concept of atoms as solid spheres.
3. J.J. Thomson: Discovered electrons and proposed the plum pudding model.
4. Ernest Rutherford: Conducted the alpha scattering experiment, leading to the nuclear model.
5. Niels Bohr: Introduced the concept of electronic shells.
6. James Chadwick: Discovered neutrons.

Highlight: The alpha scattering experiment was crucial in establishing the nuclear model of the atom, revealing that atoms are mostly empty space with a small, dense, positively charged nucleus.

The properties of subatomic particles are detailed:

• Protons: Relative charge +1, relative mass 1
• Neutrons: Relative charge 0, relative mass 1
• Electrons: Relative charge -1, relative mass very small

Vocabulary: Isotopes are different forms of the same element with the same number of protons but different numbers of neutrons.

The concept of relative atomic mass is introduced, with the formula provided for its calculation.

The Periodic Table and Element Properties

This section focuses on the organization and properties of elements in the periodic table, including group trends and characteristics of specific element groups.

The periodic table is arranged by increasing atomic number, with elements having similar properties grouped in columns. The similarities within groups are explained by the number of electrons in the outer shell.

Example: Elements in Group 1 (alkali metals) all have one electron in their outer shell, leading to similar chemical properties.

A comparison between metals and non-metals is provided, highlighting differences in conductivity, malleability, and electron behavior.

Specific groups are examined in detail:

1. Group 1 (Alkali Metals):

   • Properties: Reactive, soft, low density
   • Trends: Increasing reactivity down the group, decreasing melting and boiling points
   • Reactions with water, oxygen, and chlorine are described

2. Group 7 (Halogens):

   • Properties: 7 electrons in outer shell, diatomic molecules, low melting and boiling points
   • Trends: Increasing melting and boiling points down the group, decreasing reactivity

3. Group 8 (Noble Gases):

   • Properties: Non-metals, gases, low boiling points, unreactive
   • Trends: Increasing boiling point down the group

Highlight: The reactivity trends in Group 1 and Group 7 are opposite: Group 1 elements become more reactive down the group, while Group 7 elements become less reactive.