ATOMIC STRUCTURE Ted Talks Atomic Theory Review https://www.youtube.com/watch?v=xazQRcSCRaY

(greek for indivisible) HISTORY OF THE ATOM Democritus develops the idea of atoms 460 BC He pounded up materials in his pestle and mortar until he had reduced them to smaller and smaller particles which he called ATOMOS (greek for indivisible)

MAJOR CONTRIBUTIONS & POINTS HISTORY OF THE ATOM SCIENTIST MODEL OF THE ATOM MAJOR CONTRIBUTIONS & POINTS  DALTON (1803)   AKA: Billard Ball model Matter is made of small particles called atoms. 1. Atoms are indestructible. They cannot be created or destroyed during chemical or physical changes. Atoms of an element are identical. They have the same mass. 3. Atoms of different elements have different masses. 4. Compounds are formed by combining atoms of different elements.

Law of Conservation of Mass 8 X2Y 16 X 8 Y + Law of Conservation of Mass 2.1

Law of Definite Proportions The ratio of mass of elements in a compound is always the same Every water molecule will contain 16g of oxygen and 2 g of hydrogen 1g 1g 16g Total mass: 18g per water molecule

MAJOR CONTRIBUTIONS & POINTS HISTORY OF THE ATOM SCIENTIST MODEL OF THE ATOM MAJOR CONTRIBUTIONS & POINTS  THOMPSON (1890’s)    AKA: plum pudding model discovers electrons (negative charge) electrons scattered unevenly within an elastic sphere surrounded by a soup of positive charge to balance the electron’s charge electrons

HISTORY OF THE ATOM SCIENTIST MODEL OF THE ATOM MAJOR CONTRIBUTIONS & POINTS RUTHERFORD (1909)   Gold foil experiment – alpha (+) particles were fired at Au foil: https://www.youtube.com/watch?v=5pZj0u_XMbc FYI ONLY….If the atom is New Era Stadium Then the nucleus is a marble on the 50 yard line (1909 Nobel Prize in Chemistry) Rutherford performed the following experiment: He aimed a beam of high speed, positively charged particles called alpha particles (similar to a tennis ball) at a piece of solid gold foil (similar to a wall). He set up a special screen all around the foil to help him see where the particles went.

http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/ruther14.swf Results: 99% of the alpha particles went straight thru, 1% were deflected. Findings:: 1. Atom has a small, positively charged center 2. Atom is mostly empty space (consisting of negatively charged electrons) 2.2

MAJOR CONTRIBUTIONS & POINTS HISTORY OF THE ATOM SCIENTIST MODEL OF THE ATOM MAJOR CONTRIBUTIONS & POINTS  BOHR (1913)   AKA: Planetary model electrons move in definite, fixed orbits around the nucleus each orbit only able to contain a set number of electrons.

MAJOR CONTRIBUTIONS & POINTS HISTORY OF THE ATOM SCIENTIST MODEL OF THE ATOM MAJOR CONTRIBUTIONS & POINTS QUANTUM MODEL (1930’s)   AKA: Wave Mechanical or Electron cloud model Electrons have a distinct amount of energy and have wave-like properties. They travel in regions called orbitals. These regions are the most likely location of an electron.

Answers to pg 4 in packet: 1) A 2) C 3) B 4) C 5) D 6) C 7) D 8) A 9) A 10) A

HISTORY OF THE ATOM reviewed Atomos song http://www.youtube.com/watch?v=WK7wuTwAiBU Crash Course https://www.youtube.com/watch?v=thnDxFdkzZs Science Classroom https://www.youtube.com/watch?v=IO9WS_HNmyg

Atoms The basic unit of Matter The smallest particle of an element that retains the properties of that element. Made up of subatomic particles

ATOMIC STRUCTURE All About Atoms Particle Charge Mass Proton + charge 1amu Neutron No charge 1 amu electron - charge 1/1836

number of electrons = number of protons ATOMIC STRUCTURE He 2 Atomic number Represents the number of protons in an atom Never changes P+ equal to the number of e- 4 Mass Number the number of protons and neutrons in an atom Neutrons equal mass # - atomic # number of electrons = number of protons

HELIUM ATOM + - + - Shell proton neutron electron What do these particles consist of?

Isotopes Atoms with the same atomic number but different mass number or Atoms having the same number of protons but different numbers of neutrons Which atom is an isotope of oxygen? 1). O 2). O 3). O Isotopic notation: O or O-16 16 17 16 7 8 6 16

2.3

CHEM DO…Do You Understand Isotopes? 1. Define an isotope 2. How many protons, neutrons, and electrons are in C 14 6 ? 6 protons, 8 (14 - 6) neutrons, 6 electrons 3. How many protons, neutrons, and electrons are in C 11 6 ? 6 protons, 5 (11 - 6) neutrons, 6 electrons Isotope Maker 2.3

X H H (D) H (T) U Atomic number (Z) = number of protons in nucleus Mass number (A) = number of protons + number of neutrons = atomic number (Z) + number of neutrons # OF NEUTRONS = mass number – atomic number Mass Number X A Z Element Symbol Atomic Number H 1 H (D) 2 H (T) 3 U 235 92 238 2.3

Average Atomic Mass Average Atomic Mass of an element is the weighted average of an element’s naturally occurring isotopes. What is the average mass of cesium given the percent abundance of selected cesium isotopes? 75% Cs-133 20% Cs -132 5% Cs- 134 Practice: Guide pages 3 and 4 show work set up and solve

Bohr Model of the Atom (planetary model) Energy Levels Electrons revolve around the nucleus in one of several orbits/shells/ principal energy levels Principal energy level (PEL) is the same as the period number on the periodic table There are 7 PEL’s therefore 7 periods PEL is designated by a quantum number (n)

Alkali Earth Metal Noble Gas Halogen Alkali Metal Period Group 2.4

Location of electron According to the Bohr model, electrons are found in shells around the nucleus first shell maximum of 2 electrons second shell maximum of 8 electrons third shell max of 18 electrons fourth shell max of 32 electrons

1. Electronic Configuration ATOMIC STRUCTURE There are two ways to represent the atomic structure of an element or compound; 1. Electronic Configuration 2. Electron dot diagrams

ELECTRONIC CONFIGURATION With electronic configuration elements are represented numerically by the number of electrons in their shells and number of shells. For example; Nitrogen configuration = 2 , 5 2 in 1st shell 5 in 2nd shell 14 N 7 2 + 5 = 7

ELECTRONIC CONFIGURATION Write the electronic configuration for the following elements; 20 11 8 Na O Ca a) b) c) 16 23 40 2,8,8,2 2,8,1 2,6 14 17 Si 5 Cl B d) e) f) 11 35 28 2,8,7 2,8,4 2,3

Valence Valence shell is outermost occupied energy level and is the same as the period number in the periodic table Valence electrons are the electrons in the outer energy level of an atom

N DOT & CROSS DIAGRAMS Nitrogen With Dot & Cross diagrams elements and compounds are represented by Dots or Crosses to show electrons, and circles to show the shells. For example; X 14 Nitrogen X X N X X N X X 7

DOT & CROSS DIAGRAMS Cl O Draw the Dot & Cross diagrams for the following elements; X 16 35 X Cl a) O b) X 8 17 X X X X X X Cl X X X X X X X O X X X X X X X X X X

11 protons 11 protons 11 electrons 10 electrons 17 protons 17 protons An ion is an atom, or group of atoms, that has a net positive or negative charge. cation – ion with a positive charge If a neutral atom loses one or more electrons it becomes a cation. Na 11 protons 11 electrons Na+ 11 protons 10 electrons anion – ion with a negative charge If a neutral atom gains one or more electrons it becomes an anion. Cl- 17 protons 18 electrons Cl 17 protons 17 electrons 2.5

How many protons and electrons are in Do You Understand Ions? How many protons and electrons are in Al 27 13 ? 3+ 13 protons, 10 (13 – 3) electrons How many protons and electrons are in Se 78 34 2- ? 34 protons, 36 (34 + 2) electrons 2.5

2.5 A monatomic ion contains only one atom Na+, Cl-, Ca2+, O2-, Al3+, N3- A polyatomic ion contains more than one atom OH-, CN-, NH4+, NO3- 2.5

SUMMARY The Atomic Number of an atom = number of protons in the nucleus. The Atomic Mass of an atom = number of Protons + Neutrons in the nucleus. The number of Protons = Number of Electrons. Electrons orbit the nucleus in shells. Each shell can only carry a set number of electrons.