Atomic_Structure

Atomic Structure Content Composition of an Atom Overall Charge of an Atom - It carries no charge because a. The number of electrons = the number of protons b. The negative charges cancel out the positive charge and neutrons carry no charge Proton Number and Nucleon Number Proton Number - Different atoms have different proton numbers Nucleon Number - Mass of an electron is negligible Properties of Isotopes Property Explanation Similar chemical properties - Chemical reactions involve only the valence electrons and not the neutrons - Isotopes have the same number of protons and electrons Different Physical Properties - Physical Properties are affected by number of neutrons - Isotopes have different masses, therefore have different physical properties Arrangement of Electrons in Atoms Note: Use the acronym ‘pen’ to remember Subatomic Particle Name Properties Proton - Has a relative charge of +1 - Has a relative mass of 1 - Represented by the symbol p Neutron - Has a relative charge of 0? - Has a relative mass of 1 - Is represented by the symbol n Electron - Has a relative charge of -1 - Has a relative mass of 1 1836 - Represented by the symbol e

How are electrons arranged in an atom? - They start in the first shell on an atom (maximum of 2 electrons) - The second shell onwards can hold up to 8 electrons, the 3rd shell holds 18 electrons (beyond Calcium) and so on Periods and Groups - Periods are defined as the 7 horizontal rows of elements - Groups are defined as the 18 vertical columns of elements Isoelectronic, Isotopic, and Isotonic (General Information as seen before) - Isoelectronic means the same number of valence electrons and have the same structure - Isotopic means same number of protons - Isotonic (Not to be confused with biology) means same number of neutrons Test yourself 1. What are the 3 subatomic particles? State their i. Relative mass ii. Relative Charge iii. Symbol 2. Why are atoms electrically neutral? 3. What is a i. Proton Number ii. Nucleon Number 4. Define Isotopes? Why are isotopes have similar chemical properties but slightly different physical properties? 5. What is a valence shell? Glossary of Terms Proton Number Defined as the number of protons in the atom Nucleon Number Defined as the total number of protons and neutrons Isotopes Defined as atoms of the same element with the same number of protons and electrons, but different numbers of neutron Valence Shell Shell furthest away from nucleus of atom Valence Electrons Electrons in the valence shell Note: The general formula for calculating how many electrons can be present in a certain shell use the general formula: 2𝑛2 where n is the electron shell number (Not in syllabus but a general idea to how electrons are arranged)