Warm-up Quiz Please write the name of the following elements on p 34 Then write the Agenda and LG I.Pu II.Pt III.Sn IV.Sc V.S VI.Na

S.MORRIS 2006

The smallest particle of an element that retains the properties of the element is called an atom. Atoms are extremely small (a copper atom has a diameter of m) Atoms can be seen using a scanning tunneling microscope.

HISTORY OF THE ATOM 460 BC Democritus develops the idea of atoms Matter is composed of empty space through which solid atoms move ATOMA (greek for indivisible)

BC Aristotle ◦ One of the most influential philosophers ◦ Criticized Democritus, saying that he did not believe that the nothingness of empty space could exist

HISTORY OF THE ATOM 1808 John Dalton suggested that all matter was made up of tiny spheres that were able to bounce around with perfect elasticity and called them ATOMS

Dalton created the atomic theory model: 1. All elements are composed of tiny, indivisible particles called “atoms” 2. Atoms of the same elements are identical. *Each element is unique 3. Atoms of different elements can physically mix or chemically combine (forming compounds) 4. Chemical reactions occur when atoms are separated, joined, or rearranged Much of his theory is still accepted.

HISTORY OF THE ATOM 1886 – E. Goldstein discovered positive particles in atoms. He observed rays traveling in the opposite direction of cathode rays. These particles were termed “protons” (p+) by Ernest Rutherford in 1920.

HISTORY OF THE ATOM 1898 Joseph John Thompson passed electric current through a glass filled with gas. He discovered that a beam of negative charges travelled from the cathode (-) to the anode (+)

Joseph John Thompson He called these smaller negative particles ELECTRONS

HISTORY OF THE ATOM Thompson develops the idea that an atom was made up of electrons scattered unevenly within an elastic sphere surrounded by a soup of positive charge to balance the electron's charge 1904 like plums surrounded by pudding. PLUM PUDDING MODEL

HISTORY OF THE ATOM 1910 Ernest Rutherford oversaw Geiger and Marsden carrying out his famous gold foil experiment. they fired Helium nuclei at a piece of gold foil which was only a few atoms thick. they found that although most of them passed through. About 1 in 10,000 were deflected and, to their surprise, bounced straight back

HISTORY OF THE ATOM This experiment caused Rutherford to conclude: 1. Atoms are mostly space 2. Atoms have a solid nucleus at the center which contains most of the mass This overturned the “plum pudding model” of the time.

HISTORY OF THE ATOM They found that while most of the helium nuclei passed through the foil, a small number were deflected and, to their surprise, some helium nuclei bounced straight back. helium nuclei

HISTORY OF THE ATOM Rutherford’s new evidence allowed him to propose a more detailed model with a central nucleus. He suggested that the positive charge was all in a central nucleus. With this holding the electrons in place by electrical attraction

HISTORY OF THE ATOM 1913 Niels Bohr studied under Rutherford at the Victoria University in Manchester—parachuting into England after escaping the German invasion of Denmark. Bohr refined Rutherford's idea by adding that the electrons were in orbits. Rather like planets orbiting the sun. With each orbit only able to contain a set number of electrons. Each orbit has a fixed energy level and therefore the electrons do not lose energy.

James Chadwick Discovered the neutron, the neutral subatomic particle in the nucleus

Warm-up P 4 – Page SHOW WORK! lsotope copy LG & agenda 1. If my product has a ∆H of 50 and my reactant has a ∆ H of 20, is this an endothermic or exothermic reaction? 2. A student placed citric acid into water, and the temperature fell from 60.2 °C to 50.2 °C for g of water, how many joules were absorbed? The specific heat of water is 4.12 J/g °C.

ATOMIC STRUCTURE Subatomic particles Particle proton neutron electron Charge + charge - charge No charge 1 AMU Nil (0) Mass Location nucleus Orbitals /electron cloud AMU

Subatomic Particles The nucleus is the tiny positive core of the atom which contains most of the mass of the atom. The proton (p+) is the positively (1+) charged particle found in the nucleus of the atom. The neutron (n o ) is the particle with no charge (0) found in the nucleus of the atom.

Subatomic Particles The electron (e-) is the negatively (1-) charged particle found in the electron cloud outside of the nucleus.

ATOMIC STRUCTURE the number of protons in an atom Identifies the element the number of protons and neutrons in an atom Mass of the nucleus He 2 4 Atomic mass Atomic number number of electrons = number of protons

A tomic number = P rotons = E lectrons M ass number - A tomic number = N eutrons

Since an atom is electrically neutral, the number of protons equals the number of electrons. Atomic # = # of protons = # of electrons ElementAtomic Number Protonselectrons Pb82?? ??8? ???30

Neutrons = Atomic mass – Atomic number ElementAtomic massAtomic numberNeutrons Potassium Boron Argon

Warm-up – Page SHOW WORK! Also copy LG & agenda 1. My product has a H of 50J and my reactant has a ∆H of 20J, is this ∆H an endothermic or exothermic reaction? 2. A student placed citric acid into water, and the temperature fell from 60.2 °C to 50.2 °C for g of water, how many joules were absorbed? The specific heat of water is 4.12 J/g °C.

When you are done... Please place test and answer sheet in appropriate stacks at the front Get new Atomic Structure practice and use your periodic table to fill it out. Please also get out your note packet from last class, as we will fill in another short section today.

When you are done... Please place test and answer sheet in appropriate stacks at the front Get new Atomic Structure practice and use your periodic table to fill it out. Ms. Matte will call you to the front individually to see your test grade.

Benchmark Do not write on the test. You may use your own periodic table You may get a blank sheet of notebook paper for scratch paper Please use a pencil

Please get out your note packet from last class, as we will fill in another short section today. Copy down the Learning Goal and Agenda. We will do the Benchmark after Lunch in period 6

Ions are charged atoms Anion – atom gains an electron giving it a negative charge Cation – atom loses an electron giving it a positive charge Oh no Protons Never Change!!!!

IonAtomic Number Atomic Mass Number ProtonsNeutronsElectrons Mg Ag S Cl

IonAtomic Number Atomic Mass Number ProtonsNeutronsElectrons M Ag S Cl

In order to identify the various isotopes of an element, chemists add a number after the elements name. The number added is called the mass number and it represents the sum of the number of protons and neutrons in the nucleus. Potassium-39 Potassium-40 Potassium-41 P N o E Number of neutrons = mass number – atomic number

Atomic mass of an element is the weighted average mass of the isotopes of that element. Unit is amu Example: The atomic mass of Chlorine (Cl) is 35.5 amu. Chlorine exists naturally as 75% chlorine-35 and 25% chlorine–37 75% = 75/100=.75 25% = 25/100= x 35 amu = amu.25 x 37 amu = 9.25 amu Weighted average atomic mass of Cl = ( ) = 35.5 amu

Ex... Ex... Natural copper (Cu) consists of 2 isotopes... Natural copper (Cu) consists of 2 isotopes... Copper – 63 Copper – 63 Copper – 65 Copper – 65 69% 69% 31% 31% To calculate avg. mass... To calculate avg. mass... mass x abundance for each isotope Step 1 : Step 2 : add the two values from step 1 together 63 x.69 = 65 x.31 = amu

Isotopic Symbol X = element symbol A = mass number Z = atomic number