Chapter 2Atoms and Elements : LecturePLUS Timberlake 1 Chapter 2Atoms and Elements The Atom
Atomic Number and Mass Number
Isotopes
Atomic Theory : LecturePLUS Timberlake 2 Atomic Theory Atoms are building blocks of elements
Similar atoms in each element
Different from atoms of other elements
Two or more different atoms bond in simple ratios to form compounds
Subatomic Particles : LecturePLUS Timberlake 3 Subatomic Particles Particle Symbol Charge Relative
Mass
Electron e- 1- 0
Proton p+ + 1
Neutron n 0 1
Location of Subatomic Particles : LecturePLUS Timberlake 4 Location of Subatomic Particles 10-13 cm
electrons
protons
neutrons
10-8 cm nucleus
Atomic Number : LecturePLUS Timberlake 5 Atomic Number Counts the number
of
protons
in an atom
Atomic Number on the Periodic Table : LecturePLUS Timberlake 6 Atomic Number on the Periodic Table 11
Na Atomic Number Symbol
All atoms of an element have the same number of protons : LecturePLUS Timberlake 7 All atoms of an element have the same number of protons 11
Na 11 protons Sodium
Learning Check : LecturePLUS Timberlake 8 Learning Check 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
Solution : LecturePLUS Timberlake 9 Solution 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
Mass Number : LecturePLUS Timberlake 10 Mass Number Counts the number
of
protons and neutrons
in an atom
Atomic Symbols : LecturePLUS Timberlake 11 Atomic Symbols Show the mass number and atomic number
Give the symbol of the element
mass number
23 Na sodium-23
atomic number 11
Number of Electrons : LecturePLUS Timberlake 12 Number of Electrons An atom is neutral
The net charge is zero
Number of protons = Number of electrons
Atomic number = Number of electrons
Subatomic Particles in Some Atoms : LecturePLUS Timberlake 13 Subatomic Particles in Some Atoms 16 31 65
O P Zn
8 15 30
8 p+ 15 p+ 30 p+
8 n 16 n 35 n
8 e- 15 e- 30 e-
Isotopes : LecturePLUS Timberlake 14 Isotopes Atoms with the same number of protons, but different numbers of neutrons.
Atoms of the same element (same atomic number) with different mass numbers
Isotopes of chlorine
35Cl 37Cl
17 17
chlorine - 35 chlorine - 37
Learning Check : LecturePLUS Timberlake 15 Learning Check Naturally occurring carbon consists of three isotopes, 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of these carbon atoms.
12C 13C 14C
6 6 6
#p _______ _______ _______
#n _______ _______ _______
#e _______ _______ _______
Solution : LecturePLUS Timberlake 16 Solution 12C 13C 14C
6 6 6
#p 6 6 6
#n 6 7 8
#e 6 6 6
Learning Check : LecturePLUS Timberlake 17 Learning Check An atom of zinc has a mass number of 65.
A. Number of protons in the zinc atom
1) 30 2) 35 3) 65
B. Number of neutrons in the zinc atom
1) 30 2) 35 3) 65
C. What is the mass number of a zinc isotope
with 37 neutrons?
1) 37 2) 65 3) 67
Solution : LecturePLUS Timberlake 18 Solution An atom of zinc has a mass number of 65.
A. Number of protons in the zinc atom
1) 30
B. Number of neutrons in the zinc atom
2) 35
C. What is the mass number of a zinc isotope
with 37 neutrons?
3) 67
Learning Check : LecturePLUS Timberlake 19 Learning Check Write the atomic symbols for atoms with the following:
A. 8 p+, 8 n, 8 e- ___________
B. 17p+, 20n, 17e- ___________
C. 47p+, 60 n, 47 e- ___________
Solution : LecturePLUS Timberlake 20 Solution 16O
A. 8 p+, 8 n, 8 e- 8
B. 17p+, 20n, 17e- 37Cl
17
C. 47p+, 60 n, 47 e- 107Ag
47
Atomic Mass on the Periodic Table : LecturePLUS Timberlake 21 Atomic Mass on the Periodic Table 11
Na
22.99 Atomic Number Symbol Atomic Mass
Atomic Mass : LecturePLUS Timberlake 22 Atomic Mass Atomic mass is the weighted average mass of all the atomic masses of the isotopes of that atom.
Example of an Average Atomic Mass : LecturePLUS Timberlake 23 Example of an Average Atomic Mass Cl-35 is about 75.5 % and Cl-37 about 24.5% of natural chlorine.
35 x 75.5 = 26.4
100
35.5
37 x 24.5 = 9.07
100