Chapter 5

What are the Subatomic Particles? Proton Neutron Electron

The Atom and Subatomic Particles Cloud model Bohr Model (a) (b) Cloud of negative charge (2 electrons) Electrons Nucleus Neutrons Protons

Subatomic Particles are. . . Neutrons Found in the nucleus of the atom Have no charge (neutral) Have a mass of 1.0087amu Protons Found in the nucleus Have a positive charge have a mass of 1.0073 amu Electrons Found orbiting the outside of the nucleus Have a negative charge, a mass of 0.0006 If the atom has no charge there are the same number of electrons to protons

Subatomic Particle Particle Mass (amu) Charge Location Proton 1.0073 + Nucleus Neutron 1.0087 Neutral Electron 0.0006 - Electron Cloud

Reading the Key on a Periodic Table: The Mass Number: Shows the Atomic Mass as a decimal, round that to a whole number to write the Mass Number. Includes # of protons plus # of neutrons. Symbol: Can be one Uppercase letter and one lower case letter or one uppercase Letter only! Atomic Number: This provides the total number of Protons in the element’s atom.

Atomic Structure Atomic Mass: 39 Symbol: K Element: Potassium Mass Number : Includes the averaged mass of the number of protons and neutrons added together. This number is equal to the number of protons plus the number of neutrons. Atomic Mass: 39 Symbol: K Element: Potassium Atomic Number: 19

Atomic Number: 15 7N Nitrogen Mass Number Atomic Number Tells you the total number of protons in the nucleus. When an atom has no charge/neutral, the number of protons are equal to the number of electrons! Elements on the Periodic Table are placed in order of the Atomic Number 15 7N Nitrogen Mass Number Atomic Number

How to Solve for the number of Neutrons? Subtract the Atomic Number from the Mass Number. OR Subtract the Number of protons from the Mass Number Subtract the Number of Electrons from the Mass Number.

Aristotle Democritus Greek philosopher Believed that there were only four elements of matter: water fire Earth air Greek philosopher Believed that matter cannot be divided into small pieces forever. He named the smallest piece an atomos, Atomos is Greek for atom. Atomos means indivisible. Atom: the building block of all matter.

Dalton: The Proposed Atomic Theory All elements are composed of atoms. Atoms are indivisible and indestructible. Atoms of the same element are exactly alike. Atoms of different elements are not alike. Compounds are formed by the joining of atoms of two or more elements.

Thomson’s Model 1897: Thomson proposed that the atom is made of small particles. He explained that there were positive and negative charges scattered throughout. ”plum pudding”

Rutherford’s Model Proposed that the atom is mostly empty space filled with positive charges. Proposed that the positive charged particles were in the center of the atom, called the nucleus. Outside the nucleus were negative electrons scattered throughout the edge of the atom.

Niels Bohr 1913: Bohr believed that the electrons traveled in a definite orbit with certain energy levels and certain distances from the nucleus. Each energy level can hold a certain amount of electrons. 2-8-18-32-32

The Bohr Model According to the Bohr model each energy level can hold a certain number of electrons. Starting from the first energy level outside of the nucleus: Level 1: 2 electrons Level 2: 8 electrons Level 3: 18 electrons Level 4: 32 electrons Level 5: 32 electrons

Modern Atomic Model Today we believe that the electrons do not travel a certain path. They do have a certain energy level. They are always moving Electrons can gain or lose energy and bounce up energy levels or down energy levels.

Drawing The Bohr Model and writing the electron configuration sequence According to the Bohr model, each energy level can hold a certain number of electrons. Energy Levels, starting from the first energy level outside of the nucleus : Level 1: 2 electrons Level 2: 8 electrons Level 3: 18 electrons Level 4: 32 electrons Level 5: 32 electrons How do you write out an electron configuration?2-8-18-32-32 Write out and draw the Electron Configuration Sequence and the Bohr Model for each of the following: Example 1: Sr Example 2: U

Element’s Key and the Bohr Model: Second shell Helium 2He First Third Hydrogen 1H 2 He 4.00 Atomic mass Atomic number Element symbol Electron-shell diagram Lithium 3Li Beryllium 4Be Boron 3B Carbon 6C Nitrogen 7N Oxygen 8O Fluorine 9F Neon 10Ne Sodium 11Na Magnesium 12Mg Aluminum 13Al Silicon 14Si Phosphorus 15P Sulfur 16S Chlorine 17Cl Argon 18Ar Figure 2.8

What is an Isotope? Isotope: An atom of the same element that has the same number of protons but different number of neutrons. The Mass Number will change if an isotope exists. Proton number remains the same! Remains the same element.

What is a Quark? Theory states that there is a different particle that makes up the particles found in the nucleus, known as a Quark. The proton and neutron are composed of three different quarks that make up their charge or no charge. Quarks that make up a Proton: +2/3 +2/3 -1/3 = +1 Quarks that make up a Neutron: +2/3 -1/3 -1/3 = 0

You complete me!! The Octet Rule Atoms want to achieve a complete outer shell of 8 electrons, with exception to helium. Helium only has 2 electrons and has a complete outer shell of two. How do atoms achieve this happiness?? By forming bonds. We can represent the completion of the outer shell by drawing a picture known as the Lewis Dot Diagram.

Closure Exit Ticket Explain how you observed atomic forces in one complete sentence. Draw the Bohr Model of the element Phosphorous. Find the following for phosphorous: Number of protons Number of neutrons Number of electrons Mass number Atomic number.

The Four Forces Electromagnetic Strong Weak gravity

Electromagnetic Force Electromagnetic force: an attraction or repulsion between particles. If the particles have the same charge they are repelled. Opposite charges attract Electrons are kept in orbit because of opposing attraction for the proton But what keeps the positive protons from repelling each other???

Strong Force Opposes the electromagnetic force’s repulsion of protons! It is the glue for the nucleus! Without the strong force the atom would not stay together. Only works when the protons are close. It is the strongest of the forces.

Weak Force: Gravity: Is the power for the sun the weakest force Is responsible for radioactive decay Radioactive decay: is when the neutron changes into a proton and electron Gravity: the weakest force Is the force of attraction exerted between all objects in nature. Not clearly understood

Closure Which force is the weakest and why? Which two forces keep the atom’s structure?