the periodic table organizes all of the known elements according to their chemical properties. they...
TRANSCRIPT
The periodic table organizes all of the known elements according to their chemical properties.
They can be grouped into three major cateogories: metals, non-metals and metalloids.
staircase line
• Metals have a shiny, metallic lustre.
• Metals are good conductors of heat and electricity.
• Metals are malleable.
For example, tin (Sn) can be hammered into very thin sheets without breaking
• Metals are ductile.
They can be drawn into long wires.
• All metals are solids at room temperature, except for mercury (Hg), which is a liquid.
tin
silver
Typical metallic solid and it’s “sea of electrons:”
sulphur
• Nonmetals are dull.
• Nonmetals do not conduct heat well and do not conduct electric currents.
• Nonmetals are brittle.
• Nonmetals are solid, liquid or gas at room temperature.
iodine
• Metalloids have characteristics of both metals and nonmetals.
arsenic
• Metalloids are often brittle solids.
• Metalloids conduct electricity, but not as well as metals.
silicon
boron
(1834-1907) Dimitri Mendeleev
The first periodic table was invented by Dimitri Mendeleev in 1872.
7 periods
18 groups or families
alkali metals
alkaline earth metals halogens
noble gases
All atoms are made up of three subatomic particles:
1) proton psymbol:
2) neutron0nsymbol:
3) electron esymbol:
Protons and neutrons are located in the nucleus.
The mass of a proton or neutron is about 1800 times the mass of an electron.
Electrons are found in energy levels around the nucleus.
The atomic number of an element indicates the number of protons it has.
An atom of any element is electrically neutral, so the number of positive charges (protons) is equal to the number of negative charges (electrons).
State the number of protons for atoms of each of the following:
1) sodium:
2) carbon:
3) chlorine:
11
6
17
The elements on the periodic table are
organized by increasing atomic number!
Atoms of the same element have the same number of protons, but can have different numbers of neutrons.
Isotopes are atoms of the same element that contain different numbers of neutrons.
To differentiate between isotopes of a given element, we use a number called the mass number.
The mass number is a number equal to the total number of protons and neutrons in the nucleus of an atom.
AZ X
element symbol
mass number
atomic number
Isotope notation:
Three naturally occurring isotopes of carbon:
126 C 13
6 C 146 C
The bottom number is sometimes not written because you can determine the atomic number from the symbol.
Isotopes of TinSn-1120.97%
Sn-1140.65% Sn-115
0.34%
Sn-11614.53%
Sn-1177.68%
Sn-11824.23%Sn-119
8.59%
Sn-12032.59%
Sn-1224.63%
Sn-1245.79%
Any sample of an element found in nature is a mixture of different isotopes. Each isotope will occur in different proportions, usually given as a percentage.
For example:Each of these isotopes contains 50 protons.
The atomic mass of an element that is listed on the periodic table is called the atomic molar mass.
This value is calculated as the average mass of all of the isotopes of an element, taking the percent abundance into account.
Isotopes of TinSn-1120.97%
Sn-1140.65% Sn-115
0.34%
Sn-11614.53%
Sn-1177.68%
Sn-11824.23%Sn-119
8.59%
Sn-12032.59%
Sn-1224.63%
Sn-1245.79%
Since the mass of individual atoms is so small, it is not convenient to use a unit like grams (g).
Instead, we use the atomic mass unit (amu).
An atom of carbon-12 was assigned an exact mass of 12.00 amu.
For example, an atom twice as heavy has a mass of 24.00 amu, and an atom half as heavy has a mass of 6.00 amu.
Then the relative masses of all other atoms is determined by comparing each to the mass of an atom of carbon-12.
An atom has 14 protons and 20 neutrons.
1) Its atomic number is :
A) 14 B) 16 C) 34
2) Its mass number is :
A) 14 B) 16 C) 34
3) The element is:
A) Si B) Ca C) Se
4) Another isotope of this element is :
A) B) C)3416 X 34
14 X 3614 X
Write the atomic symbols for atoms with the following:
A. 8 p+ , 8 n0 , 8 e-
B. 17 p+ , 20 n0 , 17 e-
C. 47 p+ , 60 n0 , 47 e-
168O
3717 Cl
10747 Ag
An atom of zinc has a mass number of 65.
1) The number of protons in the zinc atom:
A) 30 B) 60 C) 65
2) The number of neutrons in the zinc atom:
A) 30 B) 35 C) 65
3) The mass number of a zinc atom with 37 neutrons is:
A) 37 B) 65 C) 67
read pages 28 – 34 (up to Formation of Ions)
Worksheets: Line Master 4 - Atomic Mass and Mass Number
Line Master 5 - Atoms, Protons, and Electrons
# p+
# n0
A model that shows the placement of electrons around the nucleus of an atom or ion.
Energy levels contain electrons that are similar in energy and distance from nucleus.
Low energy electrons are closest to the nucleus.
Each level can hold a certain maximum number of electrons before it is full:
Level Max. # of Electrons
1 2
2 8
3 8
All the elements in a group have the same electron configuration in their outermost shells. Electrons in the outer shell that is not full are called valence electrons.
Noble gases have no valence electrons, their outer shell is full. That is why they are so stable and non-reactive.
The period number (horizontal row) that an element is in is the same as the number of energy levels the atom has.
12 n0
12 p+
2 e-
8 e-
2 e-
12 n0
12 p+
2 e-
8 e-
2 e-
Draw energy level diagrams for the following isotopes:
a)2412 Mg
OR:
For neutral atoms, the number of
protons equals the number of electrons.
Excellent!!
17 n0
15 p+
2 e-
8 e-
5 e-c)32 P
11 n0
9 p+
2 e-
7 e-b)20
9 F
Given the diagram, write the symbol.
12 n0
14 p+
2 e-
8 e-
d)
2614Si
7 n0
5 p+
2 e-
3 e-e)
125 B
4 e-
An ion is a an atom (or a group of atoms) that has a positive or negative electric charge.
Recall that an atom of any element is neutral, so the number of protons equals the number of electrons.
The formation of an ion is called ionization, and is the result of an atom either gaining or losing electrons.
The number of protons only changes in nuclear reactions,
never in the formation of ions.
Cations are positively charged ions.
Ant-ion?
Anions are negatively charged ions.
They are formed when a metal atom loses valence electrons (electrons in the outermost energy level).
They are formed when a non-metal atom accepts electrons into its outer energy level.
The octet rule says that atoms tend to gain, lose or share electrons so as to have eight electrons in their outer electron shell.
Atoms gain or lose electrons so that they have the same number of electrons as the nearest noble gas.
Some metal atoms, depending on the nature of the chemical reaction, can form stable ions with more than one charge.
For example copper atoms will lose either one or two electrons.
+Cu2+Cu
These elements are called multivalent, and the first charge given on the periodic table is the most common.
Symbol Atomic # Protons Electrons Neutrons Mass # Charge
Ag
35
82
8 10
Cu 60
7 -3
47 47 47
35
61 108 0
Br 35
Pb
42 77 0
82 82 123 205 0
O2- 8 8 16 -2
29 29 29 31 0
N3- 7 10 7 14
read pages 34 – 38 (except p. 37)
A2.1 Check and Reflect
#’s 1 - 12