The Atom & Chemical Bonds Packet #5 Chapter #2

Introduction to Atoms & Elements The smallest particle of an element Elements are composed of atoms Element A substance composed of atoms having an identical number of protons in each nucleus. A substance that cannot be decomposed into simpler substances 11/23/2018 11:43:05 PM

A Closer Look at the Atom Two “broad” regions Interior & Exterior Interior Region is called the Nucleus Protons Have a positive charge Neutrons Have a neutral charge (no charge) Exterior Region is called the Electron Shell/Cloud Electrons Negative charge Surround the atom Used in the formation of chemical bonds Valence Electrons Helps determine what type of bonds are made Helps determine how many bonds are made 11/23/2018 11:43:05 PM

The Helium Atom

The Periodic Chart The Periodic Chart Is a list of all elements, but more importantly, it lists the characteristics of the atoms that make up each element. The list provides the number of protons, the atomic number, and the atomic mass of the atom found within a particular element. Hydrogen is the lightest of all elements and is a colorless and a highly flammable gas

The Periodic Chart & Elements The Equation The Periodic Chart shows the atomic number and atomic mass of the elements Atomic Number (Z) The number of protons in the nucleus of an atom Atomic Mass (A) The absolute atomic mass of an atom Equation A = Z + N N = number of neutrons in the nucleus of an atom 11/23/2018 11:43:05 PM

Question If the atomic mass of an element is 29, and the number of neutrons is 15, what element am I talking about? A = Z + N 29 = Z + 15 Z = 29 - 15 Z = 14 What element has an atomic number of 14? Si (Silicon) 11/23/2018 11:43:05 PM

Models that Represent the Atom The Bohr Model Models that Represent the Atom

Introduction I The Bohr Model is the simplest modern picture of the structure of the atom. Developed by Danish physicist Niels Bohr Shows The number of protons and neutrons located within the nucleus of the atom. The electrons spinning within the exterior region in specified areas known as shells.

Electrons & Shells Electrons spin within specified regions called shells. However, it must be noted that shells are composed of separate regions known as orbitals More to come later. Each shell holds a specified maximum number of electrons 1st Energy Level 2 electrons 2nd Energy Level 8 electrons 3rd Energy Level 18 electrons **8 electrons for elements found in row #3 only 4th Energy Level/Shell 32 electrons Examples of Carbon, Oxygen and Nitrogen Bohr Model 11/23/2018 11:43:05 PM

Electrons in the Most Outer Shell Electrons found in the most outer shell are called valence electrons These electrons are used in the formation of chemical bonds Valence Not the same as valence electrons The number of electrons required to fill the most outer shell

Movement of Electrons from Shell to Shell

Movement of Electrons Between Shells I Electrons have the capability of moving When electrons move from a low energy level to one that is higher, energy is absorbed. Exergonic reaction Requires the input of energy Endothermic reaction Reaction that absorbs energy in the form of heat When electrons move from a high energy level to one that is lower, energy is lost. Endergonic reaction Energy is lost Exothermic reaction Reaction that releases energy in the form of heat

Isotopes

Isotopes One of two or more atoms with very similar properties. However, the atomic mass is different. The atomic number remains the same. In order to change the atomic mass, if the atomic number is the same, then the number of neutrons must be changed. Examples

Electron Shells & Orbitals

Orbitals & Electron Configuration Describes the volume of space around a nucleus in which the electron is most likely to be found There are four different types of orbitals that have the ability to hold a different maximum amount of electrons S = 2 P = 6 D = 10 F = 14 Important to remember that orbitals make up shells

Orbital & Shell Connection Recall Orbitals are represented by letters See last slide Shells will be represented by numbers that hold different maximum numbers of electrons 1st shell = 2 electrons 2nd shell = 8 electrons 3rd shell = 18 electrons (8 for elements in the 3rd row) 4th shell = 32 electrons How are those numbers calculated? Illustration on board

Representing Orbitals Orbitals, surrounding different atoms, are represented in a form known as the electron configuration. Illustration of electron configuration on the board Carbon Oxygen Nitrogen Hydrogen