OCR GCSE Combined Science: Atomic Structure and Periodic Table Trends

OCR GCSE Combined Science: Atomic Structure and Periodic Table Trends

1. Atomic Structure: Building Blocks of Matter

a) Early Models:

• Dalton's Model (1803): Proposed atoms as tiny, indivisible spheres.
• Thomson's Model (1897): Discovered electrons, leading to the "plum pudding" model - a positively charged sphere with electrons embedded.
• Rutherford's Model (1911): Conducted the famous gold foil experiment, demonstrating a nucleus containing protons, surrounded by a cloud of electrons.

b) Modern Atomic Model:

• Protons: Positively charged particles found in the nucleus.
• Neutrons: Neutral particles found in the nucleus.
• Electrons: Negatively charged particles orbiting the nucleus in shells.
• Atomic Number (Z): Number of protons in the nucleus, defining the element.
• Mass Number (A): Total number of protons and neutrons in the nucleus.
• Isotopes: Atoms of the same element with the same number of protons but different numbers of neutrons.

c) Electron Configuration:

• Electrons occupy specific energy levels called shells.
• Shell 1: Holds up to 2 electrons.
• Shell 2: Holds up to 8 electrons.
• Shell 3: Holds up to 18 electrons.
• Electron Configuration: The arrangement of electrons in shells.

2. The Periodic Table: Organizing the Elements

a) Mendeleev's Periodic Table (1869):

• Arranged elements by increasing atomic mass, noticing recurring patterns in their properties.
• Left gaps for undiscovered elements, predicting their properties.

b) Modern Periodic Table:

• Elements are arranged by increasing atomic number.
• Periods (Rows): Elements in the same period have the same number of electron shells.
• Groups (Columns): Elements in the same group have the same number of valence electrons (electrons in the outermost shell), resulting in similar chemical properties.

c) Periodic Trends:

• Atomic Radius: The distance between the nucleus and the outermost electron.
• Ionization Energy: The energy required to remove an electron from an atom.
• Electronegativity: The tendency of an atom to attract electrons in a chemical bond.

3. Reactivity of Metals and Non-Metals

a) Metals:

• General Properties: Lustrous, malleable, ductile, good conductors of heat and electricity, tend to lose electrons.
• Reactivity: Increases down a group and decreases across a period.
• Reactions with Water: More reactive metals react vigorously with water, forming metal hydroxides and releasing hydrogen gas.
• Reactions with Oxygen: Metals react with oxygen to form oxides.

b) Non-Metals:

• General Properties: Dull, brittle, poor conductors of heat and electricity, tend to gain electrons.
• Reactivity: Decreases down a group and increases across a period.
• Reactions with Oxygen: Non-metals react with oxygen to form oxides.

4. Practical Skills: Observing Reactivity Patterns

• Experimental Setup: Design and conduct experiments to observe the reactions of metals and non-metals with water, oxygen, and acids.
• Observations: Record observations carefully, noting the speed of reaction, color changes, gas production, and any other changes.
• Conclusions: Draw conclusions about the relative reactivity of different elements based on the observed reactions.

5. Assessment: Key Concepts and Skills

• Understanding of Atomic Structure: Be able to define and relate terms like atomic number, mass number, isotopes, and electron configuration.
• Knowledge of Periodic Table Trends: Explain the trends in atomic radius, ionization energy, and electronegativity across periods and down groups.
• Reactivity of Metals and Non-Metals: Describe the general properties and reactivity of metals and non-metals, giving examples of their reactions.
• Practical Skills: Demonstrate the ability to design and conduct experiments to investigate the reactivity of elements, analyze data, and draw conclusions.

Remember to study the OCR GCSE Combined Science specification thoroughly for specific requirements and exam-related information.