Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Bellwork • Which of the following is most likely a pure substance? A- a smooth cake batter B- a glass of water that tastes salty C- a dark gray solid that attracts iron filings D- a sample of air captured from the atmosphere Outline • • • • • • Bellwork Quiz- It’s TUESDAY!!! YOU KNOW THE RULES!!! New Vocabulary ATOMS!!!! Review Closure (Homework) New Vocabulary • • • • • • • • Electron Nucleus Proton Neutron Atomic number Atomic mass Isotope Valence electron S.MORRIS 2006 HISTORY OF THE ATOM 460 BC Democritus develops the idea of atoms he pounded up materials in his pestle and mortar until he had reduced them to smaller and smaller particles which he called ATOMA (greek for indivisible) 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 HISTORY OF THE ATOM 1898 Joseph John Thompson found that atoms could sometimes eject a far smaller negative particle which he called an ELECTRON HISTORY OF THE ATOM 1904 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 like plums surrounded by pudding. PLUM PUDDING MODEL HISTORY OF THE ATOM 1910 Ernest Rutherford oversaw Geiger and Marsden carrying out his famous 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 hit HISTORY OF THE ATOM helium nuclei gold foil helium nuclei 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. 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 However, this was not the end of the story. HISTORY OF THE ATOM 1913 Niels Bohr studied under Rutherford at the Victoria University in Manchester. 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. Bohr’s Atom electrons in orbits nucleus HELIUM ATOM Shell proton + - N N + electron What do these particles consist of? - neutron Bell work What was Niels Bohr’s prediction about the location of the electrons in an atom? A. Electrons pair with protons and stay in the nucleus of the atoms. B. Electrons can be found at various levels within an energy cloud surrounding the nucleus. C. Electrons orbit the nucleus in well-defined energy levels or orbitals. D. Electrons are scattered randomly in a positive background matrix. ATOMIC STRUCTURE Particle Charge Mass proton + ve charge 1 neutron No charge 1 electron -ve charge nil Atomic Structure • Atoms are composed of 2 regions: – Nucleus: the center of the atom that contains the mass of the atom – Electron cloud: region that surrounds the nucleus that contains most of the space in the atom Electron Cloud Nucleus Describe Electron Electrons are negatively charged particles that surround the atom's nucleus. Electrons were discovered by J. J. Thomson in 1897. Electrons determine properties of the atom. Chemical reactions involve sharing or exchanging electrons. Describe Nucleus The nucleus is the central part of an atom. It is composed of protons and neutrons. The nucleus contains most of an atom's mass. It was discovered by Ernest Rutherford in 1911. Describe Neutron • Neutrons are uncharged particles found in the atomic nucleus. Describe Proton • Protons are positively charged particles found in the atomic nucleus. Protons were discovered by Ernest Rutherford.. B. Subatomic Particles ATOM ATOM NUCLEUS NUCLEUS ELECTRONS ELECTRONS PROTONS PROTONS NEUTRONS NEUTRONS POSITIVE CHARGE NEUTRAL CHARGE Most of the atom’s mass. NEGATIVE CHARGE NEGATIVE CHARGE in a neutral atom Atomic Number equals the # of... A. Chemical Symbols • Capitals matter! • Element symbols contain ONE capital letter followed by lowercase letter(s) if necessary. Metal that forms bright blue solid compounds. Co vs. CO Poisonous gas. ATOMIC STRUCTURE He 2 4 Atomic number the number of protons in an atom Atomic mass the number of protons and neutrons in an atom number of electrons = number of protons How do the subatomic particles balance each other? • In an atom: – The protons = the electrons • If 20 protons are present in an atom then 20 electrons are there to balance the overall charge of the atom—atoms are neutral – The neutrons have no charge; therefore they do not have to equal the number of protons or electrons How do we know the number of subatomic particles in an atom? • Atomic number: this number indicates the number of protons in an atom – Ex: Hydrogen’s atomic number is 1 • So hydrogen has 1 proton – Ex: Carbon’s atomic number is 6 • So carbon has 6 protons **The number of protons identifies the atom. Ex. 2 protons = He, 29 protons = Cu How do we know the number of subatomic particles in an atom? • Mass number: the number of protons and neutrons in the nucleus – Ex: hydrogen can have a mass of 3. Since it has 1 proton it must have 2 neutrons – # of neutrons = mass # - atomic # Determining the number of protons and neutrons • Li has a mass number of 7 and an atomic number of 3 – Protons = 3 (same as atomic #) – Neutrons= 7-3 = 4 (mass # - atomic #) • Ne has a mass number of 20 and an atomic number of 10 – Protons = 10 – Neutrons = 20 - 10= 10 What about the electrons? • The electrons are equal to the number of protons – So e- = p = atomic # • Ex: He has a mass # of 4 and an atomic # of 2 – p+ = 2 – no = 2 – e- = 2 Determine the number of subatomic particles in the following: • Cl has a mass # of 35 and an atomic # of 17 – p+ = 17, no = 18, e- = 17 • K has a mass # of 39 and an atomic # of 19 – P+ = 19, no = 20 e- = 19 ATOMIC STRUCTURE Electrons are arranged in Energy Levels or Shells around the nucleus of an atom. • first shell a maximum of 2 electrons • second shell a maximum of 8 electrons • third shell a maximum of 8 electrons ATOMIC STRUCTURE There are two ways to represent the atomic structure of an element or compound; 1. 2. Electronic Configuration Dot & Cross 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 2 in 1st shell 5 in 2nd shell configuration = 2 , 5 2 + 5 = 7 N 7 14 ELECTRONIC CONFIGURATION Write the electronic configuration for the following elements; a) Ca 20 b) Na 40 2,8,8,2 d) Cl 17 35 2,8,7 11 23 c) 2,8,1 e) Si 14 28 2,8,4 O 8 16 2,6 f) B 5 11 2,3 DOT & CROSS DIAGRAMS 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 Nitrogen X X N XX X X N 7 14 DOT & CROSS DIAGRAMS Draw the Dot & Cross diagrams for the following elements; X 8 17 X a) O b) Cl 35 X 16 X X X X X X X X X Cl X X X X X O X X X X X X X X X SUMMARY 1. The Atomic Number of an atom = number of protons in the nucleus. 2. The Atomic Mass of an atom = number of Protons + Neutrons in the nucleus. 3. The number of Protons = Number of Electrons. 4. Electrons orbit the nucleus in shells. 5. Each shell can only carry a set number of electrons.