Inside The Atom

Atom

• Particles which make up matter

Element

• Substances made of 1 type of atom

Proton

• Charge: Positive

• Location: Nucleus

• Relative Mass: 1

Neutron

• Charge: Neutral

• Location: Nucleus

• Relative Mass: 1

Electron

• Charge: Negative

• Location: Electron Shells

• Relative Mass: (1/1800 of a proton) or 0

Nucleus

Only the nucleus contributes to the mass of an atom. Thus mass number = protons + neutrons

Electron Shells

• Electron Shells orbit the nucleus in “shells” due to the attraction between protons and electrons

• Shells have a capacity

• Shells have specific energy levels

  • Further from nucleus = higher energy

Bohr Diagram

Electron Order Per Shell:

1. North

2. South

3. East

4. West

   • Repeat

Atom History

Democritus (400 BC)

The idea that something can continously be cut until it was so small and became “uncuttable” and were considered “atomos” = atoms

John Dalton (1808)

• Shows that matter consists of indivisible atoms

• Atoms arrange in different combinations to make different compounds

J.J Thompson (1904)

• discovers that atoms are divisible and are made up of negatively charged particles called electrons, which are positioned in a positively charged space.

• Plum Pudding

Ernest Rutherford (1911)

• Discovers that atoms have a nucleus and all of its positive charge is concentrated there, and the rest is mostly empty space

• Contrasts with “Plum Pudding” idea

Niels Bohr (1913)

• Suggests that instead electrons are randomly distributes, they orbit around the nucleus

Erwin Schrodinger ( 1920s )

• Suggests that electrons didn’t orbit in a perfect circle and were more ‘buzzing’ around the nucleus

• Classifies the hyperactive shape is an orbital

Quantum Mechanical Model

• Same as the Schrodinger yet it suggests neutrons and protons are positioned in the nucleus

Proof Of Atoms: Brownian Motion

• Suggests the irregular movement of suspended particles

• Reason: Due to collisions between particles and atoms

Gold Foil Experiment

• Suggests atoms contain a positively charged nucleus and atoms are largely comprised of empty space

Groups And Periods

Group - Columns on the table (18)

Period - Rows on the table (7)

Patters Of The Table

• Elements in a group have the same number of valence electrons

  • Valence electrons are electrons in the outermost shell of an atom

  • Exception Helium

• Elements in a period have the same number of occupied electron shells

Metals

General Properties:

• Good Conductors

• Lustrous

• Malleable

• Ductile

• Can undergo erosion

Subsets Of Metals

• Group 1: Alkali Metals

  • Most reactive metals

• Group 2: Alkali Earth Metals

  • Second most reactive metals

• Group 3-12: Transition Metals

  • Do not follow most reactivity trends

Non-Metals

General Properties:

• Poor Conductors

• Dull

• Brittle when solid

• Mostly Gases

Subsets of Non-Metals

• Group 18: Noble Gases

  • Non reactive (Full valence shells)

• Group 17: Halogens

  • Most reactive Non-Metals

Metalloids

General Properties:

• Intermediate of Metal and Non-Metal properties

• Stronger conductor than non-metals but weaker than metals

• Solids can be shiny or dull

• Ductile

• Malleable

Reactivity Trends

• Reactivity is dependent on how likely and element will achieve a full valence shell

  • Metals: By losing electrons

  • Non-Metals: By gaining electrons

• Most reactive Metal: Francium

• Most reactive Non-Metal: Fluorine

Reactivity Trends: Metals

• Across a period metal reactivity decreases

• Down a group metal reactivity increases

Reactivity Trends: Non-Metals

• Across a period, Non-Metal reactivity increases

• Down a group, Non-Metal reactivity decreases