(2.2) the periodic table (p118-121). matter is made of atoms
TRANSCRIPT
(2.2) The Periodic Table
(p118-121)
Matter is Made of Atoms
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.
Periodic Table of the Elements (p450)
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(n0) 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 massZ = atomic number
A = # p+ plus # n0
Z = # p+ (and # e- for neutral atom)
A - Z = # n0
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
6429 Cu
CLASS WORK
Complete and hand in BLM 2-15 BLM 2-17
Did you complete and hand inWB p38-43?
(2.2) The Periodic Table
(p118-121)
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 Mg2+
Magnesium atom loses 2 valence electrons
Nitride Ion
N N3-
Nitrogen atom gains 3 valence electrons
Let’s Practice!
Element # p+ #n0 #e- Bohr Diagram of Atom
Bohr Diagram
of Ion
Ion
11 H
42 He
73 Li
Let’s Practice Some More!
Element # p+ #n0 #e- Bohr Diagram of Atom
Bohr Diagram
of Ion
Ion
2311 Na
4018 Ar
CLASS WORK
Complete and hand in the Bohr Diagrams hand out.