Download The diameter of a Ni atom is

Gems 160 - January 18, 2006
• Homework for Chapter 1 due today
• Chem in the news on Friday - Sarah Roeschley
• Lab handouts for Thursday
• Today
• Elements in our world
• Ch. 2, parts of an atom
•
Compounds ==>
•
Elements ==> ??
•
Atoms
•
Atomos - Greek for indivisible - the smallest particle of
an element that we can identify as that element
•
How small is small ?
•
14.3 billion Ni atoms equal the
diameter of a nickel. What is the
diameter of a single Ni atom?
5¢
2.1 cm
The diameter of a Ni atom is
1.
3% 2.
76%3.
5% 4.
3% 5.
5% 6.
8%
6.81 x 10-9 cm
6.8 x 109 cm
1.47 x 10-10 cm
1.47 x 1010 cm
3.5 x 10-10 cm
3.5 x10-12 m
1
•
How small is small in terms of mass?
•
A nickel weighs 5.0 grams and contains 5.13 x 1022 atoms.
What is the mass of a single atom?
•
Review use of scientific notation, see Appendix A.
•
Review appendix B and C for metric units and conversions.
•
1 lb = 454 g, 1 kg = 1000g; How many kg is a 170 lb man?
•
Difference between mass and weight•
Mass is a fundamental property, not affected by location defined as the resistance to acceleration
•
Weight results from the force of gravity acting on mass
Which has the greatest weight?
1.
44%
2.
18%
3.
0%
4.
33%
5.
5%
100 g of gold on the moon
100 g of styrofoam peanuts on the lab bench
100 g of wood floating in the ocean
100 g of helium in a balloon in this room
All have the same weight
The world around us is composed of • Compounds ==>
• Elements ==>
• Atoms ==>
• Use common knowledge and consult with a
colleague to answer the following:
2
The most abundant element in the
earths crust is
11%1.
68%2.
8%
3.
13%4.
0%
5.
Silicon
Iron ore
Copper
Oxygen
Aluminum
The most abundant element by
weight in the ocean is
67%1.
18%2.
13%3.
3%
0%
4.
5.
Hydrogen
Sodium
Oxygen
Chlorine
Water
The most abundant gas in the
atmosphere by volume is
1. Carbon dioxide
Oxygen
46%3. Nitrogen
3% 4. Hydrogen
0% 5. Methane
0% 6. Gasoline
5%
46%2.
3
The most abundant element in the
universe in terms of number of atoms is
13%1.
67%2.
8%
3.
10%4.
3%
5.
Helium
Hydrogen
Oxygen
Nitrogen
Neon
Two ways of seeing the world around us
• Macroscopic
• Microscopic
• Compound: combination of • Compound: a molecule
two or more elements in a
formed when atoms with
specific weight ratio.
different atomic numbers
combine in a specific ratio
• Element: pure substance
• Element: substance whose
that cannot be decomposed or
atoms all have the same
converted to a simpler
atomic number (number of
substance.
protons).
• Both are characterized by
• Both are characterized by the
their physical and chemical
nature of their sub-atomic
properties
structure.
As a result of studies over a long time the atomic theory
has been well developed - it provides a basis for
understanding why different elements and compounds
have the physical and chemical properties that they do
• Atoms have parts
–
–
–
•
Protons
Neutrons
Electrons
Atoms have structure
–
–
Inner nucleus with protons and neutrons
Outer “orbitals” with electrons
4
•
In all atoms the number of
electrons equals the number of
protons.
•
In ions the number of electrons
may be less than the number of
protons (cations +) or more than
the number of protons (anions –)
Symbolic structure for the atoms
•
•
•
•
X is the element symbol
A
Z
Z is the number of protons
Z determines X - periodic table
A is the sum of protons + neutron (mass number)
X
• Write the notation for the following:
• Carbon with 6 neutrons
• Carbon with 8 neutrons
!
Chlorine with 18 neutrons is
Cl
18 Cl
3. 1735Cl
4. 3517Cl
25%
1.
25%
2.
25%
25%
18
35
36
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
5
Hydrogen with 0 neutrons is
H
2. 1 H
3. 01H
4. 1-1H
25%
1.
1
1
0
25%
25%
25%
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
Symbolic structure for the atoms
•
•
•
•
•
Write the notation for the following:
Chlorine with 18 neutrons
Chlorine with 19 neutrons
Hydrogen with 0 neutrons
Hydrogen with 2 neutrons
• Atoms with the same number of protons but
different numbers of neutrons are called isotopes
Isotopes and the real world
• A careful study of Cl atoms shows that 75.8%
have a mass number of 35 and 24.2% have a
mass number of 37.
• What is the average mass number for Cl atoms?
• The average mass number is the atomic weight
that is found on the periodic table (sec 3.6)
• Most chemical calculations are based on the
atomic weight, because any sample of atoms will
be an average of all the isotopes.
6
Describe the relation between the following
symbols and each term in the list
84
87
88
0.5% 38 Sr, 9.9% 86
38 Sr, 7.0% 38 Sr, 82.6% 38 Sr
!
•
•
•
•
•
•
•
Atomic mass unit (amu)
Atomic number
Hand in your answers for these
Mass number
terms at the start of class on
Atomic weight
Friday. Go to the discussion
board for a copy.
Isotope
Protons
Neutron
Periodic table and atomic structure
• All protons and neutrons add to the nucleus
in an equal manner
• Electrons add to outer orbitals, but not all
the orbitals are equal
Electrons, periodic table and atomic structure
• Each row in the table describes an orbital
– A place where electrons are found
– The orbital is also called a quantum shell
• For our purposes
– Row 1 = shell 1, holds up to 2 electrons
– Row 2 = shell 2, holds up to 8 electrons
(a set of 2 and a set of 6)
– Row 3 = shell 3, holds up to 18 electrons
(a set of 2, a set of 6 and a set of 10)
– Row 4 = shell 4, holds up to 32 electrons
7
Electrons, periodic table and atomic structure
• How are the shells different from each other
– 1 is closest to the nucleus, lowest energy
– 2 is further away from nucleus, more energy
– 3 is further away than 2, more energy than 2
– etc
8