The Nucleus Chapter 14 Section 2

What is an Atom? Most basic units of matter Everything in world made up of atoms Air you breathe Desk you are sitting in Your body Smallest particle of an element with all the properties of the element that can combine with other atoms to form a molecule

ATOM SIZE 1 PENNY = 2X1022 Cu & Zn ATOMS (20,000,000,000,000,000,000,000) Thickness of aluminum foil is about 50,000 aluminum atoms stacked

How many different types of Atoms are there? 92 naturally occurring elements(different types of atoms 25 synthetic elements (made by scientists in laboratory)

Matter made of atoms of only one kind What is an Element? Matter made of atoms of only one kind Example: piece of aluminum foil Element Aluminum—many of same kind of atom Each atom has same properties: shiny, metal, flexible

Most of the mass of an atom is found in the nucleus 1 amu = 1.7 X 10 -24 g

PROTONS (+) Found In Nucleus Positive charge Mass = 1 amu (atomic mass unit-SI unit for measuring mass of atomic particles)

NEUTRONS (o) Found In Nucleus Neutral=no charge Mass = 1 amu (atomic mass unit)

ELECTRONS(-) Found In Electron Cloud Outside The Nucleus In a neutral Atom: # of protons= # of electrons The atom has no charge Mass = almost ZERO

ELECTRONS(-) Comparing the masses 1,800 electrons = 1 proton

Parts of the Atom Particle Charge Location Weight Proton Positive (+) Nucleus 1 amu Neutron Neutral (no charge) Electron Negative (-) Electron cloud 0.018 amu Almost zero amu = atomic mass unit

Two-Dimension Model Protons & neutrons placed together in center—nucleus Electrons orbit nucleus in space called electron cloud Electron cloud organized into energy levels 1st level—can hold 2 e- 2nd level—can hold 8 e- 3rd level—can hold 18 e-

Identifying Numbers How does the nucleus in an atom of one element differ from the nucleus of an atom of another element? Atoms of different elements contain different numbers of protons

Identifying Numbers Atomic Number —number of protons in the nucleus of an atom Hydrogen, smallest atom, has 1 proton Uranium, heaviest natural atom, has 92 protons atoms are identified by the number of protons The number never changes without changing identity of element

Identifying Numbers Isotopes –atoms of the same element that have different numbers of neutrons element carbon has 6 protons (atomic number) Isotopes of carbon can have 6, 7, or 8 neutrons Mass number—number of neutrons plus the number of protons

Isotopes

Naming Isotopes CARBON-12 CARBON-14 WRITE THE NAME OF THE ELEMENT FOLLOWED BY A HYPHEN AND THE MASS NUMBER OF THE ISOTOPE CARBON-12 CARBON-14

Isotopes of Carbon Carbon-12 Carbon-13 Carbon-14 Mass Number 12 13 14 # protons 6 # neutrons 7 8 # electrons Atomic Number Average atomic mass—average mass of the mixture of an element’s isotopes

Isotopes of Hydrogen Example: http://education.jlab.org/glossary/isotope.html

Isotopes of Hydrogen

Reading a Periodic Table

Synthetic Elements Elements that are made in labs by smashing atomic particles into a target element Elements with atomic numbers 93 to 112, and 114 are synthetic elements

Radioactive Decay The release of nuclear particles and energy. When those nuclear particles released are protons the atomic number changes and that element changes into another element-Transmutation

Two protons and two neutrons Alpha Particles Two protons and two neutrons Alpha particles are ejected during transmutation Ex. Americium-241 becomes Neptunium All atomic particles still exist just in different combinations

Beta Particles High-energy electron that comes from the nucleus Electron in nucleus(aka Beta Particle) comes from a neutron that has changed to a proton and an electron Electron(Beta Particle) is released but proton stays in the nucleus This increases the # of protons in the nucleus and changes the element http://www.youtube.com/watch?v=HGE1JstspM4&feature=related

Radioactive Decay Is random-can’t tell which atoms will decay, but can predict how long it will take for half of the radioactive isotope to decay-

HALF-LIFE The amount of time it takes for half of a sample of the element to decay. Can range in length from fractions of a second to billions of years. http://www.khanacademy.org/video/half-life?playlist=Chemistry http://www.youtube.com/watch?v=-kHK3rF7R7M&NR=1

Carbon Dating Used to determine the age of dead animals, plants(once living things-how long ago they lived) Half-life for Carbon-14 is 5730 years Carbon-12 makes up 99% Carbon-13 makes up 1% Carbon-14 makes up 1 part per million Carbon-14 is radioactive and it is this radioactivity which is used to measure age. knowing how many carbon-14 atoms something had before it died can only be guessed at. The assumption is that the proportion of carbon-14 in any living organism is constant.

Uranium-238 Used to determine the age of rocks U-238 decays into lead 206 Half-life is 4.5 billion years Problems- may have already been lead in rock and some isotopes may have migrated out of the rock-giving inaccurate dating

Uses of Radioactive Isotopes Medical Uses: Tracer elements or radioisotopes-used to help diagnose disease Environmental Uses: Tracer elements watches how a plant uses a certain element(phosphorus) In Pesticides/Fertilizers to follow the pesticide to see how it moves through an ecosystem Water resources http://www.youtube.com/watch?v=K5Ks2X5TphI

http://www. authorstream http://www.authorstream.com/Presentation/Susann-48726-radioactivity-1-Slide-2-PLUM-PUDDING-MODEL-ATOM-4-5-6-7-8-9-10-11-12-13-14-Education-ppt-powerpoint/

QUIZ Chapter 4, Section 2 Particle found in the nucleus that has no charge Contains most of the mass of an atom Negatively charged particle found outside the nucleus Particle found in the nucleus that is positively charged

QUIZ Chapter 4, Section 2 The simplest atom is the __________ atom. Particle with an unequal number of protons and electrons SI unit used for the masses of atomic particles. Draw and label a model of an atom. Include the three particle and their charges.

QUIZ Chapter 4, Section 2 Calculate the number of protons, neutrons and electrons in carbon-14.