ATOMIC STRUCTURE S.MORRIS 2006

Learning Outcomes Define atom and element Get an idea of the size of an atom Basic structure of the atom Types, numbers of, and properties of subatomic particles in an atom

LecturePLUS Timberlake Atomic Theory Atoms are building blocks of elements = Atom is the smallest particle of matter that can exist by itself Similar atoms in each element Different from atoms of other elements Two or more different atoms bond in simple ratios to form compounds LecturePLUS Timberlake

HISTORY OF THE ATOM ATOMS John Dalton 1808 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 ELECTRON Joseph John Thompson 1898 found that atoms could sometimes eject a far smaller negative particle which he called an ELECTRON

HISTORY OF THE ATOM PLUM PUDDING MODEL 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 Ernest Rutherford 1910 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 gold foil helium nuclei 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 However, this was not the end of the story. 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 Niels Bohr 1913 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

Structure of the atom Nucleus Electrons orbiting the nucleus

HELIUM ATOM + - + - Shell proton neutron electron What do these particles consist of? https://www.youtube.com/watch?v=lP57gEWcisY

ATOMIC STRUCTURE Particle Charge Mass proton + ve charge 1 neutron No charge 1 electron -ve charge nil

Location of Subatomic Particles 10-13 cm electrons protons neutrons 10-8 cm nucleus LecturePLUS Timberlake

LecturePLUS Timberlake Atomic Number Counts the number of protons in an atom LecturePLUS Timberlake

LecturePLUS Timberlake Periodic Table Represents physical and chemical behaviour of elements Arranges elements by increasing atomic number Repeats similar properties in columns known as chemical families or groups LecturePLUS Timberlake

LecturePLUS Timberlake Periodic Table 1 2 3 4 5 6 7 8 11 Na LecturePLUS Timberlake

Atomic Number on the Periodic Table 11 Na Atomic Number Symbol LecturePLUS Timberlake

All atoms of an element have the same number of protons 11 Na 11 protons Sodium LecturePLUS Timberlake

LecturePLUS Timberlake Learning Check AT 1 State the number of protons for atoms of each of the following: A. Nitrogen 1) 5 protons 2) 7 protons 3) 14 protons B. Sulfur 1) 32 protons 2) 16 protons 3) 6 protons C. Barium 1) 137 protons 2) 81 protons 3) 56 protons LecturePLUS Timberlake

LecturePLUS Timberlake Solution AT 1 State the number of protons for atoms of each of the following: A. Nitrogen 2) 7 protons B. Sulfur 2) 16 protons C. Barium 3) 56 protons LecturePLUS Timberlake

LecturePLUS Timberlake Number of Electrons An atom is neutral The net charge is zero Number of protons = Number of electrons Atomic number = Number of electrons LecturePLUS Timberlake

LecturePLUS Timberlake Mass Number Counts the number of protons and neutrons in an atom LecturePLUS Timberlake

LecturePLUS Timberlake Atomic Symbols Show the mass number and atomic number Give the symbol of the element mass number 23 Na sodium-23 atomic number 11 LecturePLUS Timberlake

LecturePLUS Timberlake More Atomic Symbols 16 31 65 O P Zn 8 15 30 p+ p+ p+ n n n e- e- e- LecturePLUS Timberlake

Learning Objectives Bohr Structure Electronic Configuration Drawing structure of atoms

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

1. Electronic Configuration ATOMIC STRUCTURE There are two ways to represent the atomic structure of an element or compound; 1. Electronic Configuration 2. 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 configuration = 2 , 5 7 2 in 1st shell 5 in 2nd shell N 2 + 5 = 7 14

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 17 14 5 Cl Si B d) e) f) 11 35 28 2,8,7 2,8,4 2,3

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 Nitrogen N 7 X X N X X 14 X X

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

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.

When an atom loses an electron it gets a positive charge When an atom loses an electron it gets a positive charge. When an atom gains an electron it gets a negative charge.

How many neutrons and electrons are there in the ion 45 Sc +3 21