Atomic Theory Atomic theory is the study of the nature of atoms and how atoms combine to form all types of matter. (a)Bohr Diagram of Sulfur atom -contains 16 electrons and 16 protons (b) Diagram of the nucleus of the atom
Valence Shell The outermost shell of an atom is called the valence shell. This shell is where chemistry happens! A stable atom has full valence shell.
The Periodic Table of Elements The periodic table contains a standard set of symbols to represent the elements, laid out in a specific pattern. It is based on the organization developed by Dmitri Mendeleev in 1869.
Table Characteristics Metals, non-metals and metalloids Periods (or rows) Groups (or families)
Common Chemical Groups There are 18 chemical groups on the periodic table, however four of these groups are of particular interest Alkali metals (group 1) Alkaline earth metals (group 2) Halogens (group 17) Noble gases (group 18)
Alkali Metals Group 1 Soft, silver-grey metals that react easily with water and with oxygen NOTE: H is not an alkali metal.
Alkaline Earth Metals Group 2 Silver-grey metals that are harder and less reactive than group 1 metals. Reactive atoms that combine easily with other atoms.
Halogens Group 17 Coloured non-metals that are VERY reactive Can be a solid, a liquid or a gas
Noble Gases Group 18 Non-metals that are colourless, odourless gases and inert. Unreactive atoms that do not combine easily with other atoms.
Elements of the Periodic Table Each element on the periodic table is represented by a square. The information in the box may vary between different periodic tables, but usually includes the following: Name, symbol, atomic number, atomic mass and ion charge.
Atomic Number The atomic number is the number of protons in an atom of an element. Ex: Atomic number of fluorine is 9
Atomic Mass The atomic mass of an element is a measure of the average mass of an atom of that element. Ex: Atomic mass of fluorine is 19 Hydrogen has a mass of 1 Potassium as a mass of 39.1 so it is 39 times heaver than hydrogen.
Atomic Mass When measuring the mass of an atom of an element all three sub-atomic particles are included. electron (e - ), proton (p + ), neutron(n 0 ) Electrons are so small that it hardly makes a difference in the mass if they are included or not. So the mass is made up of the much more massive protons and neutrons.
General Notation A Z A = atomic mass Z = atomic number A = # p + plus # n 0 Z = # p + (and # e - for neutral atom) A - Z = # n 0
Atomic Mass and Number One can calculate the number of neutrons from the atomic mass and the atomic number. Atomic Mass = protons + neutrons Atomic Number = number of protons Atomic mass – Atomic number = neutrons
Neutron Number Copper has an atomic mass of 63.5 Rounded to the whole number 64 Copper has an atomic number of 29 So copper has 64 – 29 = 35 neutrons 64 29 Cu
CLASS WORK Complete and hand in BLM 2-15 BLM 2-17 Did you complete and hand in WB p38-43?
Ion Charge When an atom gains or loses electrons it becomes an ion. An atom that gains electrons becomes a negatively charged ion called an anion. Non-metals gain electrons. An atom that loses electrons becomes a positively charged ion called a cation. Metals lose electrons.
Magnesium Ion Mg Mg 2+ Magnesium atom loses 2 valence electrons
Nitride Ion N N 3- Nitrogen atom gains 3 valence electrons
Let’s Practice! Element# p + #n 0 #e - Bohr Diagram of Atom Bohr Diagram of Ion Ion 1 1 H 4 2 He 7 3 Li
Let’s Practice Some More! Element# p + #n 0 #e - Bohr Diagram of Atom Bohr Diagram of Ion Ion 23 11 Na 40 18 Ar
CLASS WORK Complete and hand in the Bohr Diagrams hand out.